Bio 202 Essay
Exam 2 Study Guide Bio 202 Chapter 13
Differentiate a virus from a bacterium
Describe the chemical and physical structure of both an enveloped and a nonenveloped virus. (Include a description of the envelope, capsid, and core
The nucleic acid of a virus is protected by a protein coat called the capsid. The structure of the capsid is ultimately determined by the viral nucleic acid and accounts for most of the mass of a virus, especially of small ones. Each capsid is composed of protein subunits called capsomeres. In some viruses, the proteins composing the capsomeres are of a single type; in other viruses, several types of protein may be present. In some viruses, the capsid is covered by an envelope, which …show more content…
usually consists of some combination of lipids, proteins, and carbohydrates. Some animal viruses are released from the host cell by an extrusion process that coats the virus with a layer of the host cell’s plasma membrane; that layer becomes the viral envelope. In many cases, the envelope contains proteins determined by the viral nucleic acid and materials derived from normal host cell components. Depending on the virus, envelopes may or may not be covered by spikes, which are carbohydrate-protein complexes that project from the surface of the envelope. Some viruses attach to host cells by means of spikes. capsomere Nucleic Acid
Envelope
Spikes
Viruses whose capsids are not covered by an envelope are known as nonenveloped viruses. The capsid of a nonenveloped virus protects the nucleic acid from nuclease enzymes in biological fluids and promotes the virus’s attachment to susceptible host cells. Short summary:
-chemical composition: the envelope usually consists of some combination of lipids, proteins, and carbohydrates; some animal viruses are released from the host cell by an extrusion process that coats the virus with a layer of the host cell's plasma membrane; that layer becomes the viral envelope. in many cases, the envelope contains proteins determined by the viral nucleic acid and materials derived from normal host cell components
non envelope: just has a protein coat over it called a capsid
-physical structure: depending on the virus, envelopes may or may not be covered by spikes; enveloped viruses are roughly spherical
Briefly describe how viruses are classified. Give an example of a family, genus, and common name for a virus.
New, fast DNA sequencing allows the International Committee on Taxonomy of Viruses to group viruses into families based on genomics and structure. The suffix -virus is used for genus names; family names end in viridae; and order names end in -ales.
In formal usage, the family and genus names are used in the following manner:
Family Herpesviridae, genus Simplexvirus, (in text) (Herpesvirus in powerpoint) species: human herpesvirus 2.
A viral species is a group of viruses sharing the same genetic information and ecological niche (host range). Specific epithets for viruses are not used. Thus, viral species are designated by descriptive common names, such as human immunodeficiency virus (HIV), with subspecies (if any) designated by a number (HIV-1).
Family names end in -viridae
Genus names end in -virus
Viral species: a group of viruses sharing the same genetic information and ecological niche (host)
Common names are used for species
Subspecies are designated by a number
Describe how bacteriophages are cultured.
-bacteriophages can be grown either in suspensions of bacteria in liquid media or in bacterial cultures on solid media
-the use of solid media makes possible the plaque method for detecting and counting viruses
Bacteriophages form plaques on a lawn of bacteria
Describe how animal viruses are cultured.
Animal viruses may be grown in living animals or in embryonated eggs
Animal and plant viruses may be grown in cell culture Continuous cell lines may be maintained indefinitely
List three techniques used to identify viruses.
Cytopathic effects – visible effects on viral-infected cells (see next slide)
Serological tests
Detect antibodies against viruses in a patient
Use antibodies to identify viruses in neutralization tests, viral hemagglutination, and Western blot
Nucleic acids (molecular tests)
List and describe the steps in a typical animal virus life cycle
Animal:
Attachment: Viruses attach to cell membrane
Penetration by endocytosis or fusion
Uncoating by viral or host enzymes
Biosynthesis: Production of nucleic acid and proteins
Maturation: Nucleic acid and capsid proteins assemble (also referred to as “Assembly”)
Release by budding (enveloped viruses) or rupture
List and describe the steps in a typical retrovirus life cycle.
Retrovirus:
Attachment: Tall fibers attach to cell wall proteins
Penetration: Viral DNA is injected into host cell
Uncoating: unnecessary
Biosynthesis: Production of phage DNA and proteins. (in cytoplasm)
Maturation: viral components are assembled into virions
Release: Host cell lysis, virions are released
Define oncogene and transformed cell.
Oncogene – cancer-causing alterations to cellular DNA affect parts of the genome
Transformed cell: When activated, oncogenes (cancer causing genes) transform normal cells into cancerous cells. Viruses that are capable of producing tumors are called oncogenic viruses.
Discuss the relationship between DNA- and RNA-containing viruses and cancer.
Molecular biological research shows that the mechanisms of the diseases are similar, even when a virus does not cause the cancer. A human cancer-causing virus was discovered and isolated in 1972 by American bacteriologist Sarah Stewart.
Oncogenes can be activated to abnormal functioning by a variety of agents, including mutagenic chemicals, high-energy radiation, and viruses. Viruses capable of inducing tumors in animals are called oncogenic viruses, or oncoviruses. Approximately 10% of cancers are known to be virus-induced. An outstanding feature of all oncogenic viruses is that their genetic material integrates into the host cell’s DNA and replicates along with the host cell’s chromosome. This mechanism is similar to the phenomenon of lysogeny in bacteria, and it can alter the host cell’s characteristics in the same way.
Provide an example of a latent viral infection.
Acute infection
Latent
Persistent
Latent viral infection: Varicellovirus – the chicken pox can exist in latent form & come about as shingles
Differentiate persistent viral infections from latent viral infections and name a group of viruses that are well-known for causing latent infections.
A latent viral infection is one in which the virus remains in the host cell for long periods without producing an infection. Stress or some other cause may trigger its appearance or reappearance. This is the case with herpes simplex virus, which causes cold sores, and chickenpox virus, which causes shingles.
A persistent viral infection refers to a disease process that occurs gradually over a long time and is generally fatal. Persistent viral infections are caused by conventional viruses, where the virus accumulates over a long time period. These are typically fatal. Ex: Subacute sclerosing panencephalitis (Measels)
Define prion and list several prion-related diseases
Proteinaceous infectious particle. These diseases are caused by the conversion of a normal hostglycoprotein called PrPC (for cellular prion protein) into an infectious form called PrPSc (for scrapie protein). The gene for PrPC is located on chromosome 20 in humans. Recent evidence suggests that PrPC is involved in regulating cell death.
Inherited and transmissible by ingestion, transplant, and surgical instruments
Spongiform encephalopathies: sheep scrapie,
Creutzfeldt-Jakob disease, fatal familial insomnia mad cow disease chronic wasting disease
Explain how bacteriophage may be used for control of bacteria (either in the environment, or in the body)
Because we know how they form, we have certain drugs & processes that can inhibit or prevent some of these steps in order to control the bacteria.
Chapter 7
Refer to: text book page 191, chart on physical methods of microbial growth page 201-202, chart on chemical methods page 200, chart on microorganism resistance
Discuss the historical roles played by Ignaz Semmelweis and Joseph Lister in preventing the spread of infection. (you will probably have to do a little Internet research to find out more information about these two men)
Semmelweis discovered incidences of childbirth fever could be reduced by use of hand disinfection. He made the connection that student doctors who delivered women that came down with childbirth fever had recently been handling cadavers. His contemporaries rejected the idea of cleanliness because it went against standard medical beliefs and practices of the time.
Lister was a pioneer of antiseptic surgery. Using Pasteur’s advances in microbiology, he successfully introduced carbolic acid (phenol) to sterilize surgical instruments and to clean wounds. This led to a reduction in post-operative infections.
Define the following key terms related to microbial control: sterilization, disinfection, antisepsis, biocide, germicide, bacteriostasis, and asepsis
Sterilization: removing all microbial life (100% of life forms)
Disinfection: removing microorganisms from inanimate surfaces
Antisepsis: removing microorganism from living tissue
Biocide: a substance capable of killing microorganisms
Germicide: same as biocide
Bacteriostasis: inhibiting microbes (NOT killing)
Asepsis: the absence of contamination by unwanted organisms
Describe the effects of microbial control agents on cellular structures.
Alternation of membrane permeability (detergents)
Damage to proteins (denaturing- heat)
Damage to nucleic acids (radiation)
Compare the effectiveness of moist heat (boiling, autoclaving, pasteurization) and dry heat.
Moist heat:
Boiling water- 100oC, Kills vegetative cells, most viruses and protozoa within 10 minutes. Endospores and some viruses are NOT killed; DOES NOT STERILIZE (disinfects)
Autoclave: Minimum 121oC, 15 psi and 15 minutes will STERILIZE
Pasteurization: DOES NOT STERILIZE. Except for ultra high temp process, which sterilizes but is not technically pasteurization.
Dry heat:
STERILIZATION: kills by oxidation
Examples: flaming, incinerators, hot-air sterilization
List the 2 goals of pasteurization.
Safety: kills pathogens
Extend shelf life of product/reduces spoilage
Compare pasteurization (classic and HTST) to UHT. What is accomplished by UHT that is not accomplished by either pasteurization method.
Classic: 63oC for 30 min, does not sterilize
High temp, short time (HTST): 72oC for 15 seconds, does not sterilize
Ultra high temp (UHT): 140oC for less than 1 second. Sterilizes but does not affect texture and flavor of food.
Define (equivalent treatments) and provide 2 examples.
Equivalent treatment is when different treatments have the same effect on controlling microbial growth
Example: hot air treatment, 170oC for 2 hours has the same sterilization effect as autoclave at 121oC for 15 min
Describe how filtration, low temperatures, high pressure, desiccation, and osmotic pressure suppress microbial growth.
Filtration: air or fluid passes through a filter and pathogens are trapped. Filters come in different pore sizes.
Air: HEPA filter. Removes microbes >.3 microns. Often used in hospital setting.
Liquid: membrane filtration removes microbes >.22 microns. Used on heat-sensitive liquids.
Low temperature: inhibits microbial growth (bacteriostatic, does not kill). Refrig, freezer.
High pressure: denatures proteins without heat
Osmotic pressure: low osmotic pressure causes plasmolysis of bacterial cells. Example, salting meats
Dessication: drying out, prevents metabolism. Example, raisins
Explain how radiation (ionizing radiation, as well as UV radiation) kills cells.
Ionizing radiation: x-rays, gamma rays, electron beams
Damages DNA: breaks phophodiester bonds
Used on lab and hospital supplies
Hamburger, spices, some vegetables
Non-ionizing radiation: UV
Damages DNA
Sterilizing air and surfaces in hospitals, “pasteurize” cider.
Disadvantage: does not penetrate, can only sterilize surfaces.
Microwaves
Kill by heat, not really antimicrobial
List appropriate applications of ionizing and UV radiation for sterilization. (see question 9)
List the factors related to effective disinfection.
Concentration of disinfectant: more isn’t always better, some need water added to work
Organic matter: have to clean the item off before disinfecting pH Time: how long disinfecting product is in contact with contaminated surface
Interpret the results of use-dilution tests and the disk-diffusion method.
Disk diffusion: measure the zone of inhibition. The larger the zone, the better the disinfecting agent worked. You can look up the “accepted” sizes of the zone of inhibition for different bacteria to determine which are good to use
Use-dilution: method of determining the effectiveness of a disinfectant using serial dilutions. A bacteria is exposed to disinfectant then is cultured. The effectiveness of the disinfectant is determined by the number of cultures that grow after being exposed to disinfectant. Identify the methods of action and preferred uses of chemical disinfectants. **CHART PAGE 201-202***
Phenols & phenolics: disrupt plasma membrane. Used by Lister to control infection in operating rooms
Bisphenols: disrupt plasma membranes. Phisohex, triclosan
Biguanides: disrupt plasma membrane. Chlorhexidine- skin antisepsis before surgery. Perioguard, hibiclens.
Halogens:
iodophors (betadine, povidone iodine)- surgical scrub, skin prep, ANTISEPTIC
Chlorine: bleach, chloramine, chlorine dioxide gas
Alcohols: denature proteins, dissolve lipids. Require water. Hand sanitizers
Heavy metals: Ag, Hg, Cu.
Silver: neonatal gonohhreal opthalamia, burn cream
Copper: algicide
Oligodynamic action: very tiny amounts are effective
Surfactants (detergents)- quaternary ammonium compounds (quats) denature proteins, disrupt plasma membrane both antiseptics (mouthwash) and disinfectants (Lysol, clorox, cavicide)
Chemical food preservatives
Organic acids: inhibit metabolism, controls molds and bacteria in foods & cosmetics. Benzoic acid, etc.
Nitrite: prevents endospore germination. Prevents botulism in sausage, etc
Antibiotics: natamycin prevents spoilage in cheese
Aldehydes: inactivate proteins by cross-linking with functional groups
**Medical equipment use:
Glutaraldehyde (CIDEX). Will STERILIZE. Virucidal in 10 mins, sporicidal in 3-10 hours
Gaseous sterilants: ethylene oxide
Denatures proteins
Use on heat sensitive materials (plastics). Very penetrating. Can sterilize medical equip through package.
Will STERILIZE
Uses: medical supplies/equipment, plastic ware, sutures, implanted prosthetics, large equipment
Plasma (gas): newer. Free radicals destroy microbes. Used on tubular instruments (endoscopy equip)
Super critical fluids: CO2 with gaseous and liquid properties (under pressure). Used for medical implants (heart valves, organs)
Peroxygens (oxidizing agents):
Ozone- water disinfection hydrogen peroxide- don’t use on wounds; for inanimate objects, contact lenses peracetic acid- STERILIANT
Differentiate halogens used as antiseptics from halogens used as disinfectants.
Antiseptics: iodophors
Disinfectants: bleach, etc
Identify the appropriate uses for surface-active agents (quats).
Antiseptic- mouthwash
Disinfectants- Lysol, Clorox, Cavicide
List the advantages of glutaraldehyde over other chemical disinfectants.
Will STERILIZE if given long enough exposure time
Identify chemical sterilizers.
Glutaraldehyde
Ethylene oxide
Peracetic acid
Describe appropriate applications of ethylene oxide sterilization.
Medical supplies/equipment, plastic ware, textiles, sutures, lensed instruments, implanted prosthetics, large pieces of equipment
Given an item requiring disinfection of sterilization, describe the most effective method/process to accomplish this.
Explain how the type of microbe affects the control of microbial growth.
Different microbes are resistant to different methods of control.
Illustrate the hierarchy of microorganisms from those easiest to destroy to those most difficult to destroy
These are the problem microorganisms
Chapter 14
Differentiate between infection and disease and provide examples of related processes.
Infection is the invasion or colonization of the body by pathogenic microorganisms; disease occurs when an infection results in any change from a state of health.
Disease is an abnormal state in which part or all of the body is not properly adjusted or incapable of performing its normal functions. An infection may exist in the absence of detectable disease. For example, the body may be infected with the virus that causes AIDS but experience no symptoms of the disease.
The presence of a particular type of microorganism in a part of the body where it is not normally found is also called an infection-and may lead to disease. For example, although large numbers of E. coli are normally present in the healthy intestine, their infection of the urinary tract usually results in disease.
Define symbiosis and list and describe the three types of symbiosis. Relate these types of symbiosis to the microorganisms that live in and on our bodies.
The relationship between the normal microbiota and the host is called symbiosis, a relationship between two organisms in which at least one organism is dependent on the other.
3 types of SYMBIOSIS-
Commensalism: one organism benefits, and the other is unaffected. For example, Staphylococcus epidermis on the skin. These bacteria live on secretions and sloughed-off cells, and they bring no apparent benefit or harm to the host.
Mutualism: Both organisms benefit. For example, the large intestine contains bacteria, such as E. coli, that synthesize vitamin K and some B vitamins. These vitamin are absorbed into the bloodstream and distributed for use by body cells. In exchange, the large intestine provides nutrients used by the bacteria, resulting in their survival.
Parasitism: One organism benefits at the expense of the other. Many disease-causing bacteria are parasites. For example, H1N1 virus particles benefit by deriving nutrients at the expense of the host cells.
Define opportunist.
Opportunistic pathogens—those that take advantage of certain situations—such as bacterial, viral, fungal or protozoan infections that usually do not cause disease in a healthy host, one with a healthy immune system. For example, microbes that gain access through broken skin or mucous membranes can cause opportunistic infections. Or, if the host is already weakened or compromised by infection, microbes that are usually harmless can cause disease (AIDS and Pneumocystis pneumonia)
Differentiate between communicable disease and noncommunicable disease and give an example of each.
Communicable disease refers to diseases that can pass from one person to another. For example, Chickenpox, measles and genital herpes.
Non-communicable diseases occur in one person and cannot be passed on to another person. These diseases are caused by microorganisms that normally inhabit the body and only occasionally produce disease. An example is tetanus: Clostridium tetani produces disease only when it is introduced into the body via abrasions.
Communicable diseases are also known as infectious diseases, and non-communicable diseases are referred to as chronic.
Define endemic, epidemic, and pandemic and give an example of each.
Endemic disease- A disease constantly present in a population; an example of such is the common cold.
Epidemic disease- If many people in a given area acquire a certain disease in a relatively short period; influenza is an example of a disease that often achieves epidemic status.
Pandemic disease- An epidemic disease that occurs worldwide. Influenza as well as AIDS are examples.
Differentiate between acute, chronic, and latent infections.
Acute- one that develops rapidly but lasts only a short time; i.e. Influenza
Chronic- develops more slowly, and the body’s reactions may be less severe, but the disease is likely to continue or reoccur for long periods. i.e. hepatitis B
Latent- one in which the causative agent remains inactive for a time but then becomes active to produce symptoms of the disease. i.e. shingles
Differentiate between local and systemic infections.
Local Infection- One in which the invading microorganisms are limited to a relatively small area of the body. Some examples of local infections are boils and abscesses.
Systemic Infection- Microorganisms or their products are spread throughout the body by the blood or lymph. Measles is an example of a systemic infection.
Differentiate between bacteremia and septicemia.
Bacteremia refers to a bacterial invasion into blood circulation. Bacteremia can occur when you brush your teeth, pick a scab, or squeeze a zit. Bacteremia may also result from any type of dental or surgical procedure. Bacteremia may or may not cause any symptoms, depending on whether the organism was able to replicate themselves in the blood stream. For most people, the immune system should "notice" the organisms immediately and respond with specialized white blood cells to search out and destroy them. Of course, it is possible for bacteremia to progress to septicemia, especially if an individual has a weakened immune system.
Septicemia, also called blood poisoning, is a systemic infection arising from the multiplication of pathogens in the blood. This is an infection that moves rapidly and is life-threatening. Simply put, septicemia is bacteremia with replicating bacteria to cause an infection. Septicemia is a common example of sepsis (a toxic inflammatory condition arising from the spread of microbes)
Differentiate between primary infection and secondary infection.
Primary infection- an acute infection that causes the initial illness.
Secondary infection- one caused by an opportunistic pathogen after the primary infection has weakened the body’s defenses. Secondary infections of the skin and respiratory tract are common and are sometimes more dangerous than the primary infections.
List the sequence of events in the development of an infectious disease.
Incubation Period- Time between infection and onset of signs and/or symptoms.
Prodromal Period- Short time of generalized, mild symptoms preceding illness. Symptoms often include malaise and muscle aches. Not all infectious diseases have a prodromal period Period of Illness- Most severe stage of an infectious disease. Signs and symptoms are most evident at this time. Patient’s immune system has not yet fully responded. Pathogen is harming the body and causing disease. A physician typically sees the patient during this stage
Period of Decline-
Body gradually returns to a normal state of health.
Immune response and/or medical treatment begin to affect the growth and survival of the pathogen. Signs and symptoms subside. The immune response and antibody titers normally peak during this stage of infectious disease. If the patient does not recover, the disease may be fatal.
Period of Convalescence-
This is a period of recovery Damaged tissues and other body systems are repaired
Define reservoir, zoonosis, vector, and carrier, and give examples.
Reservoir- Sites were pathogens persist and go on to cause other infections are termed reservoirs of infection.
Zoonosis- a disease that occurs primarily in wild and domestic animals but can be transmitted to humans.
Vector- An arthropod that carries disease-causing organisms from one host to another.
Carrier- Organism (usually refers to humans) that harbors pathogens and transmits them to others.
List modes of transmission of infectious diseases.
Contact transmission is the spread of an agent of disease by direct contact, indirect contact or droplet transmission.
Direct contact- also known as person-to-person transmission, is the direct transmission of an agent by physical contact between its source and a susceptible host.
Indirect contact- occurs when the agent of disease is transmitted from its reservoir to a susceptible host by means of a nonliving object.
Droplet transmission- microbes are spread in mucous droplets that travel only short distances. These droplets are discharged into the air by coughing, sneezing or talking. (travel less than 1 meter)
Vehicle Transmission is the transmission of disease agents by a medium, such as water, food or air.
Waterborne transmission- pathogens are usually spread by water contaminated with untreated or poorly treated sewage. Airborne transmission- the spread of agents of infection by droplet nuclei in dust that travel more than 1 meter from reservoir to host.
Vectors- (An arthropod that carries disease-causing organisms from one host to another)
Mechanical transmission- the passive transport of the pathogens on the insect’s feet or body parts.
Biological transmission is an active process and is more complex. The arthropod bites an infected person or animal and ingests some of the infected blood.
Define and give an example of a fomite.
A fomite is a nonliving object that can spread infection (a towel, money, clothing or dishes)
Define nosocomial infection, list three common microorganisms recovered from nosocomial infections, and list the most common body sites of nosocomial infections.
A nosocomial infection does not show any evidence of being present or incubating at the time of admission to a hospital; it is required as a result of a hospital stay. (8th leasing cause of death in the U.S.)
Three common microorganisms recovered from nosocomial infections are:
Coagulase-negative staphylococci- 15% of total infections, 89% resistant to Antibiotics, most common cause of sepsis.
Staphylococcus aureus- 15% of total infections, 50% resistant to Antibiotics, most frequent cause of pneumonia.
Enterococcus spp.- 10% of total infections, 4-71% resistant to Antibiotics, most common cause of surgical wound infections.
Principal sites of nonsocial infections:
Urinary tract infections
Surgical site infections
Lower respiratory infections
Bacteremia, caused primarily by IV catheterizations
Describe what is meant by the term “compromised”. State the factors might cause a person to become compromised.
A compromised host is one whose resistance to infection is impaired by disease, therapy or burns. Two principal conditions can comprise the host; broken skin or mucous membranes, and a suppressed immune system.
List several ways in which nosocomial infections are transmitted.
Direct contact transmission from hospital staff to patient and from patient to patient.
Indirect contact transmission through fomites and the hospital’s ventilation system (airborne transmission)
Define epidemiology and state the contributions of Snow, Semmelweis, and Florence Nightingale.
Epidemiology- The science that studies when and where diseases occur and how they are transmitted.
John Snow (15 March 1813 – 16 June 1858) was an English physician and a leader in the adoption of anesthesia and medical hygiene. He is considered one of the fathers of modern epidemiology in part because of his work in tracing the source of a cholera outbreak in Soho, London, in 1854.
Ignaz Philipp Semmelweis(July 1, 1818 – August 13, 1865) was a Hungarian physician of German descent now known as an early pioneer of antiseptic procedures. Described as the "savior of mothers", Semmelweis discovered that the incidence of puerperal fever could be drastically cut by the use of hand disinfection in obstetrical clinics.
Florence Nightingale (May 12, 1820 – August 13, 1910) was a celebrated British social reformer and statistician, and the founder of modern nursing. She came to prominence while serving as a nurse during the Crimean war, where she tended to wounded soldiers. She recorded statistics on epidemic typhus in the English civilian and military populations. In 1858, she published a thousand-page report using statistical comparisons to demonstrate that diseases, poor food, and unsanitary conditions were killing
soldiers.
Synercid- Quinupristin/dalfopristin (trade name Synercid) is a combination of two antibiotics used to treat infections by staphylococci and by vancomycin-resistant Enterococcus faecium.
Linezolid is a synthetic antibiotic developed by a team at Pharmacia and Upjohn Company. It is used for the treatment of serious infections caused by Gram-positive bacteria that are resistant to several other antibiotics.
Chapter 20
Identify the contributions of Paul Ehrlich and Alexander Fleming to chemotherapy.
Ehrlich- Early 20 century, coined the term chemotherapy, speculated on the magic bullet to selectively find and destroy pathogens but not harm the host.
Fleming- Discovered Penicillin in 1928, produced by Penicillium
Name the microbes that produce most antibiotics.
Streptomyces/Actinomycetes- produce more than half, found in soil
Gram-Positive Rods- Bacillus/Paenibacillus polymyxa- endospore forming bacteria
Fungi/Mold- Cephalosporium/Penicillium
Describe the problems of chemotherapy for viral, fungal, protozoan, and helminthic infections.
Viral- the pathogen is within human hosts cells and the genetic information of the virus is directing human cells to make viruses rather than synthesize normal cell material
Fungal-Protozoan-Helminthic infections- the pathogen is a eukaryotic cell. These cells closely resemble human cells and choices of drugs are much more limited.
Define the following terms: spectrum of activity, broad-spectrum antibiotic, superinfection
Spectrum of activity- defines the range of pathogens which are sensitive to an infection
Broad spectrum antibiotics- Antibiotics that affect a broad range of gram-positive or gram negative bacteria= Ampicillin
Narrow spectrum antibiotics- Antibiotics that affect a small range of microbial types= Penicillin G, affects gram-positive bacteria but very few gram-negative
Superinfection- infection occurring after or on top of an earlier infection, esp. following treatment with broad-spectrum antibiotics. Also when growth of a target pathogen that has developed resistance to the antibiotic.
Describe how broad spectrum antibiotics may contribute to the development of superinfections.
Broad spectrum drugs destroy many normal microbiota of the host, normal microbiota ordinarily compete with and check the growth of pathogens, if the antibiotic doesn’t destroy certain organisms in the normal microbiota but does destroy their competitors, the survivors may flourish and become opportunistic pathogens. Ex Candida albicans, an overgrowth of yeast.
Identify five modes of action of antimicrobial drugs.
Inhibiting cell wall synthesis= interfere with peptidoglycan- penicilllins, cephalsoporins, bacitracin, vancomycin
Inhibition of protein synthesis= interfere with ribosomes- chlorampehenicol, erythromycin, tetracycline, streptomycin
Inhibition of nucleic acid replication and transcription= inhibits DNA or RNA synthesis- quinolones, fluoroquinolones, rifampin
Injury to plasma membrane= humans have this, hard to isolate- Polymixin B
Inhibition of essential metabolite synthesis/competitive inhibitor of enzymes- sulfanilamide, trimethoprim
Describe the mode of action of the following antibiotics: penicillin (natural and semisynthetic)- Inhibitor of cell wall synthesis- susceptible to beta-lactamase cephalosporin- Inhibitor of cell wall synthesis- susceptible to beta-lactamase, differ in spectrum and route of administration. Many generations, each slightly different vancomycin- Inhibitor of cell wall synthesis, important “last line” against antibiotic resistant S. aureus (MRSA) aminoglycosides- Inhibitor of Protein Synthesis(Streptomycin, Neomycin, Gentamycin) tetracycline- Inhibitor of protein synthesis, broad spectrum-concerns with developing teeth chloramphenicol- Inhibitor Protein Synthesis, broad spectrum, concerns can cause bone marrow production to shut down, toxic erythromycin- Inhibitor of protein synthesis- narrow spectrum sulfonamides- Competitive Inhibitor of enzymes, inhibit folic acid synthesis trimethoprim-sulfamethoxazole= Comptetive inhibitor of enzymes ex Bactrim, Septra rifampin- Inhibitor of nucleic acid synthesis, inhibits RNA synthesis ciprofloxacin- Inhibitor of nucleic acid synthesis, inhibits DNA gyrase synercid- Inhibitor of protein synthesis- used against MRSA, VRE linezolid- Inhibitor of protein synthesis- used against MRSA and VRE- Vancomycin Resistant Enterococcus Name the two major advantages of semisynthetic penicillin and identify two different semisynthetic “cillins” and which advantage they illustrate.
Semisynthetic=partly produced by mold, part added synthetically-
Extended spectrum- developed to overcome the problem of narrow spectrum of natural penicillins. Effective against many gram-negative and gram-positive bacteria. Ex ampicillin, amoxacillin
Penicillinase resistant- an enzyme produced by some bacteria that actively destroy penicillin, these penicilllins are not damaged by this enzyme. Ex Oxacillin and Methicillin
Not mutually exclusive!
Name two antimycobacterial agents and describe how these drugs act selectively against mycobacteria.
Isoniazid (INH) –inhibits mycolic acid synthesis
Ethambutol- Inhibits incorporation of mycolic acid
Used against TB!!! Rifamycin/Rifampin also used against TB
Describe how sulfa drugs inhibit microbial growth.(Competitive Inhibitors of Enzymes)
Inhibit folic acid synthesis (humans don’t make folic acid), broad spectrum, some people develop allergies
Describe significant side effects of the following antimicrobials:
Aminoglycosides (gentamicin, tobramycin, amikacin) - Used against Pseudomonas aeruginosa. Can develop ototoxicity- 8th cranial nerve and nephrotoxicity- in the kidneys, must be monitored
Tetracycline- Concerns over discoloration of teeth. Not given to pregnant women( can also cause liver problems in pregnant women) or kids under 12
Ciprofloxacin- can damage developing cartilage
Chloramphenicol- Suppresses bone marrow activity which affects the formation of blood cells, can not be given for long periods of time.
Briefly explain the modes of action of currently used antifungal drugs.
Eukaryotes such as fungi use the same mechanisms to synthesize proteins and nucleic acids as humans. Inhibition of ergosterol synthesis (fungal cell membrane, plasma membrane) Polyenes- Amphotericin B
Azoles- Miconazole, Triazoles Inhibition of cell wall synthesis- Cancidas is used against Candida and Pneumocystitis Ex. Echinocandins Inhibition of nucleic acid synthesis- Flucytocine, Diflucan Other anitfungals- Griseofulvin- affective against fungal infections in hair and nails Tolnaftate- alternative to miconazole, topical Pentamidine- used for Pneumocystis pneumonia Explain the modes of action of currently used antiviral drugs.
Nucleoside and Nucleotide Analogs- Acyclovir Famciclovir Ganciclovir Valciclovir Ribavirin Interferons-Cells infected by a virus produce interferon, which inhibits the spread of infection. “Paul Revere” proteins, messengers, Tweeters Alpha interferon- treats viral hepatitis Imiquimod- stimulates the production of interferons Enzyme inhibitors/Inhibit neuraminidase- to treat influenza Zanamivir (Relenza) Oseltamivir(Tamiflu) Inhibit uncoating- to treat influenza Amantadine Drugs for HIV Protease inhibitors- indinavir Integrase inhibitors- Fusion inhibitors Entry inhibitors Describe two tests for microbial susceptibility to chemotherapeutic agents, including one qualitative method and one quantitative method.
Diffusion methods-
Disc-Diffusion Method/ Kirby-Bauer test = Qualitative method- If the agent is effective a zone of inhibition forms around the disc, this can be measured and reported as, Sensitive, Intermediate, Resistant Results are inadequate, but it is simple and inexpensive
The E test- enables an estimate of the minimal inhibitory concentration (MIC) = the lowest antibiotic concentration that prevents visible bacterial growth. Broth dilution test- Quantitative To determine MIC and MBC- minimal bactericidal concentration
Describe the mechanisms of drug resistance (the concept map will help with this) Describe an R plasmid (Resistance Factor) and state how it contributes to the spread of antimicrobial resistance. Describe the problems in treating infections due to MDR-TB and XDR-TB, MRSA, VRSA, and VRE
Mutations lead to antibiotic resistance
Antibiotics are NOT mutagenic- do not cause mutations
4 ways of resistance
Blocking entry- altered porins
Inactivating enzymes, ex Beta lactamase
Alteration of target molecule- prevents binding of antibiotic
Efflux of antibiotic (pumps)- Membrane pumps/resistance pumps
Mutations are spread Horizontally
Conjugation
Transduction Vertically
Cell division
R plasmid (Resistance Factor)
Resistance is carried by plasmids which can jump from one piece of DNA to another
R plasmids can be transferred between bacterial cells in a population and between bacterial populations
MDR-TB and XDR-TB= Mycobacterium tuberculosis
ORSA/MRSA= Oxacillin/Methicillin Resistant Staphylococcus aureus
Vancomycin is reserved for these
Now VRSA-Vancomycin Resistant Staphylococcus aureus= treated with Synercid/Linezolid
VRE- Vancymycin Resistant Enterococcus- treated with Synercid/Linezolid
CRE/CRK- Carbepenam resistant
Describe some of the problems resulting from heavy overuse of antibiotics and include in this description the problem of use of antibiotics in livestock feeds.
Heavy overuse of antibiotics leads to resistance Using outdated or weakened antibiotics Using antibiotics for a cold Failing to complete the prescribed regimen Using someone else’s prescription
Using antibiotics in animal feed
Causing a “survival of the fittest” antibiotics kill some bacteria but other bacteria have properties that help them survive Resistance to antimicrobial drugs results in mutations, these mutations are transferred FQ- Fluoroquinolone resistant C. jejuni in humans emerged in 1990s
Not in review-
Antimicrobial drugs- interfere with the growth of microbes within a host
Antibiotics- a substance produced by a microbe that in small amounts inhibits another microbe
Selective toxicity- a drug that kills harmful microbes without damaging the host
Bactericidal- kill microbes directly
Bacteriostatic- prevents microbes from growing
Synergism- when the effect of 2 drugs together is greater than the effect of either one alone
Antagonism- when the effect of 2 drugs together is less than the effect of either one alone
Future of chemotherapeutic agents Antimicrobial peptides Broad spectrum antibiotics Nisin- lactic acid bacteria Defensins- human
CHAPTER 15
Identify the principal portals of entry
Mucous membranes, skin and the parenteral route (beneath the skin or membranes)
Define ID50 and LD50
ID50 is the number of microorganisms that will infect 50% of the population. LD50 is the amount of toxin needed to be lethal to 50% of the population
Using examples, explain how microbes adhere to host cells
The attachment between pathogen and host is accomplished by means of surface molecules on the pathogen called adhesins or ligands that bind specifically to complementary surface receptors on certain host tissue. Streptococcus mutans attaches to teeth surface via glycocalax. Escherichia coli use fimbriae to attach and Streptococcus pyogenes uses an M protein.
Describe how biofilms contribute to microbial virulence
Biofilms are resistant to antibiotic. Bacteria uses biofilms to attach, communicate and share nutrients.
Explain how capsules and cell wall components contribute to pathogenicity
Capsules resist the host’s defenses by impairing phagocytosis. The chemical nature of the capsule prevents the phagocytic cell from adhering to the bacterium. The capsule itself may be causative (S. pneumoniae). S. pyogenes produces a heat and acid resistant protein called M protein in the cell wall and surface. Capsules and biofilms resist phagocytosis and helps pathogens stick.
Compare the effects of coagulases, kinases, hyalaurinidase, and collagenase
Coagulase an enzyme that clots fibrinogen in the blood isolates bacteria by “walling off” areas in the body produced by S. aureus.
Kinase digests fibrin clots. There are 2 types Staphylokinase and Streptokinase.
Hyalurondiase is an enzyme secreted by Staph and Strep cocci. It hydrolyses hyaluronic acid which is a type of polysaccharide formed in the body. Can help diffuse meds.
Collagenase breaks down collagen by hydrolysis, produced by several species including Clostridium.
Define and give examples of antigenic variation
Antigenic variationis the mechanism by which a pathogen evades a host immune response by changing its surface proteins. It is adaptive; the most fit for the environment will survive and reproduce. N. gonorrhoeae has several copies of the Opa-encoding gene, resulting in cells with different antigens over time
Describe the function of siderophores
Siderphores are proteins that are secreted when a pathogen requires iron. They bind more steal the iron and make the iron-siderophore complex which is the delivered to the siderphore receptors on the surface of the bacteria
Provide an example of direct damage, and compare this to toxin production
Direct damage is very parasite like, the pathogen essentially takes over the host cell and consumes its nutrients and leaves its waste. The bacteria grow and may eventually lyse the cell. Most damage however is due to toxins which are poisonous substances that are produced by some microorganisms
Contrast the nature and effects of exotoxins and endotoxins
Exotoxins are proteins produced inside the bacteria and are mostly Gram positive. They are structure and or function specific. There are 3 types: A-B toxins, membrane disrupting and supreanitgens
Endotoxins are the lipid portion of lipopolysaccharides that are part of the outer membrane of the cell wall of gram-negative bacteria. The endotoxins are liberated when the bacteria die and the cell wall breaks apart
List 5 examples of exotoxins, including the organism that produces each and the effects of each specific exotoxin
Disease Bacteria Toxin Mechanism and effect
Botulism Clostridium difficile Botulinum A-B Neurotoxin prevents nerve impulse
Tetanus Clostridium tetani Tetanospasmin A-B Neurotoxin blocks nerve impulses to muscle relaxation pathway
Diptheria Corynebacterium diphtheria A-B Cytotoxin inhibits protein synthesis in nerve, heart and kidney
Antibiotic associated Clostridium membrane- enterotoxin causes
Diarrhea difficile disrupting secretion of fluids and electrolytes, result in diarrhea. Cytotoxin disrupts host cytoskeleton
Toxic shock Staph .aureus Superantigen Toxin causes secretion of fluids and electrolytes from capillaries that reduce blood vol. and lower blood pressure
List 9 cytopathic effects of viral infections
During multiplication cytocidal viruses cause the macromolecular synthesis w/in the cell host to stop
Virus causes hosts lysozomes to release their enzymes resulting in destruction of intracellular contents and host cell death
Inclusions in nucleus from Papovavirus and Adenovirus. Inclusions in cytoplasm from Rhabdovirus. Inclusions in both from Cytomegalovirus.
Viruses may cause cells to form a very large multi-nucleated cell called a synctium. From measles mumps and the common cold
May reduce cells ability to fight infection by prompting cells to reduce production of immune substance
Viral infections prompt host cell DNA to code for interferons
Viral infections can induce antigenic changes on the host cell surface. These antigenic changes elicit a host antibody response against the infected cell
Viral infections can change host chromosomes, oncogenes may be added causing cancer
Cancer causing viruses inhibit “contact inhibition” between host cells thus promoting cancer
Differentiate portals of entry and portals of exit
Portals of entry are where microorganisms enter the body, some examples are respiratory tract, gastrointestinal tract, genitourinary tract, conjunctiva, skin and the parenteral route. Portals of exit are where microorganisms exit the body and are generally the same places as entry.
Differentiate a virus from a bacterium
Describe the chemical and physical structure of both an enveloped and a nonenveloped virus. (Include a description of the envelope, capsid, and core
The nucleic acid of a virus is protected by a protein coat called the capsid. The structure of the capsid is ultimately determined by the viral nucleic acid and accounts for most of the mass of a virus, especially of small ones. Each capsid is composed of protein subunits called capsomeres. In some viruses, the proteins composing the capsomeres are of a single type; in other viruses, several types of protein may be present. In some viruses, the capsid is covered by an envelope, which …show more content…
usually consists of some combination of lipids, proteins, and carbohydrates. Some animal viruses are released from the host cell by an extrusion process that coats the virus with a layer of the host cell’s plasma membrane; that layer becomes the viral envelope. In many cases, the envelope contains proteins determined by the viral nucleic acid and materials derived from normal host cell components. Depending on the virus, envelopes may or may not be covered by spikes, which are carbohydrate-protein complexes that project from the surface of the envelope. Some viruses attach to host cells by means of spikes. capsomere Nucleic Acid
Envelope
Spikes
Viruses whose capsids are not covered by an envelope are known as nonenveloped viruses. The capsid of a nonenveloped virus protects the nucleic acid from nuclease enzymes in biological fluids and promotes the virus’s attachment to susceptible host cells. Short summary:
-chemical composition: the envelope usually consists of some combination of lipids, proteins, and carbohydrates; some animal viruses are released from the host cell by an extrusion process that coats the virus with a layer of the host cell's plasma membrane; that layer becomes the viral envelope. in many cases, the envelope contains proteins determined by the viral nucleic acid and materials derived from normal host cell components
non envelope: just has a protein coat over it called a capsid
-physical structure: depending on the virus, envelopes may or may not be covered by spikes; enveloped viruses are roughly spherical
Briefly describe how viruses are classified. Give an example of a family, genus, and common name for a virus.
New, fast DNA sequencing allows the International Committee on Taxonomy of Viruses to group viruses into families based on genomics and structure. The suffix -virus is used for genus names; family names end in viridae; and order names end in -ales.
In formal usage, the family and genus names are used in the following manner:
Family Herpesviridae, genus Simplexvirus, (in text) (Herpesvirus in powerpoint) species: human herpesvirus 2.
A viral species is a group of viruses sharing the same genetic information and ecological niche (host range). Specific epithets for viruses are not used. Thus, viral species are designated by descriptive common names, such as human immunodeficiency virus (HIV), with subspecies (if any) designated by a number (HIV-1).
Family names end in -viridae
Genus names end in -virus
Viral species: a group of viruses sharing the same genetic information and ecological niche (host)
Common names are used for species
Subspecies are designated by a number
Describe how bacteriophages are cultured.
-bacteriophages can be grown either in suspensions of bacteria in liquid media or in bacterial cultures on solid media
-the use of solid media makes possible the plaque method for detecting and counting viruses
Bacteriophages form plaques on a lawn of bacteria
Describe how animal viruses are cultured.
Animal viruses may be grown in living animals or in embryonated eggs
Animal and plant viruses may be grown in cell culture Continuous cell lines may be maintained indefinitely
List three techniques used to identify viruses.
Cytopathic effects – visible effects on viral-infected cells (see next slide)
Serological tests
Detect antibodies against viruses in a patient
Use antibodies to identify viruses in neutralization tests, viral hemagglutination, and Western blot
Nucleic acids (molecular tests)
List and describe the steps in a typical animal virus life cycle
Animal:
Attachment: Viruses attach to cell membrane
Penetration by endocytosis or fusion
Uncoating by viral or host enzymes
Biosynthesis: Production of nucleic acid and proteins
Maturation: Nucleic acid and capsid proteins assemble (also referred to as “Assembly”)
Release by budding (enveloped viruses) or rupture
List and describe the steps in a typical retrovirus life cycle.
Retrovirus:
Attachment: Tall fibers attach to cell wall proteins
Penetration: Viral DNA is injected into host cell
Uncoating: unnecessary
Biosynthesis: Production of phage DNA and proteins. (in cytoplasm)
Maturation: viral components are assembled into virions
Release: Host cell lysis, virions are released
Define oncogene and transformed cell.
Oncogene – cancer-causing alterations to cellular DNA affect parts of the genome
Transformed cell: When activated, oncogenes (cancer causing genes) transform normal cells into cancerous cells. Viruses that are capable of producing tumors are called oncogenic viruses.
Discuss the relationship between DNA- and RNA-containing viruses and cancer.
Molecular biological research shows that the mechanisms of the diseases are similar, even when a virus does not cause the cancer. A human cancer-causing virus was discovered and isolated in 1972 by American bacteriologist Sarah Stewart.
Oncogenes can be activated to abnormal functioning by a variety of agents, including mutagenic chemicals, high-energy radiation, and viruses. Viruses capable of inducing tumors in animals are called oncogenic viruses, or oncoviruses. Approximately 10% of cancers are known to be virus-induced. An outstanding feature of all oncogenic viruses is that their genetic material integrates into the host cell’s DNA and replicates along with the host cell’s chromosome. This mechanism is similar to the phenomenon of lysogeny in bacteria, and it can alter the host cell’s characteristics in the same way.
Provide an example of a latent viral infection.
Acute infection
Latent
Persistent
Latent viral infection: Varicellovirus – the chicken pox can exist in latent form & come about as shingles
Differentiate persistent viral infections from latent viral infections and name a group of viruses that are well-known for causing latent infections.
A latent viral infection is one in which the virus remains in the host cell for long periods without producing an infection. Stress or some other cause may trigger its appearance or reappearance. This is the case with herpes simplex virus, which causes cold sores, and chickenpox virus, which causes shingles.
A persistent viral infection refers to a disease process that occurs gradually over a long time and is generally fatal. Persistent viral infections are caused by conventional viruses, where the virus accumulates over a long time period. These are typically fatal. Ex: Subacute sclerosing panencephalitis (Measels)
Define prion and list several prion-related diseases
Proteinaceous infectious particle. These diseases are caused by the conversion of a normal hostglycoprotein called PrPC (for cellular prion protein) into an infectious form called PrPSc (for scrapie protein). The gene for PrPC is located on chromosome 20 in humans. Recent evidence suggests that PrPC is involved in regulating cell death.
Inherited and transmissible by ingestion, transplant, and surgical instruments
Spongiform encephalopathies: sheep scrapie,
Creutzfeldt-Jakob disease, fatal familial insomnia mad cow disease chronic wasting disease
Explain how bacteriophage may be used for control of bacteria (either in the environment, or in the body)
Because we know how they form, we have certain drugs & processes that can inhibit or prevent some of these steps in order to control the bacteria.
Chapter 7
Refer to: text book page 191, chart on physical methods of microbial growth page 201-202, chart on chemical methods page 200, chart on microorganism resistance
Discuss the historical roles played by Ignaz Semmelweis and Joseph Lister in preventing the spread of infection. (you will probably have to do a little Internet research to find out more information about these two men)
Semmelweis discovered incidences of childbirth fever could be reduced by use of hand disinfection. He made the connection that student doctors who delivered women that came down with childbirth fever had recently been handling cadavers. His contemporaries rejected the idea of cleanliness because it went against standard medical beliefs and practices of the time.
Lister was a pioneer of antiseptic surgery. Using Pasteur’s advances in microbiology, he successfully introduced carbolic acid (phenol) to sterilize surgical instruments and to clean wounds. This led to a reduction in post-operative infections.
Define the following key terms related to microbial control: sterilization, disinfection, antisepsis, biocide, germicide, bacteriostasis, and asepsis
Sterilization: removing all microbial life (100% of life forms)
Disinfection: removing microorganisms from inanimate surfaces
Antisepsis: removing microorganism from living tissue
Biocide: a substance capable of killing microorganisms
Germicide: same as biocide
Bacteriostasis: inhibiting microbes (NOT killing)
Asepsis: the absence of contamination by unwanted organisms
Describe the effects of microbial control agents on cellular structures.
Alternation of membrane permeability (detergents)
Damage to proteins (denaturing- heat)
Damage to nucleic acids (radiation)
Compare the effectiveness of moist heat (boiling, autoclaving, pasteurization) and dry heat.
Moist heat:
Boiling water- 100oC, Kills vegetative cells, most viruses and protozoa within 10 minutes. Endospores and some viruses are NOT killed; DOES NOT STERILIZE (disinfects)
Autoclave: Minimum 121oC, 15 psi and 15 minutes will STERILIZE
Pasteurization: DOES NOT STERILIZE. Except for ultra high temp process, which sterilizes but is not technically pasteurization.
Dry heat:
STERILIZATION: kills by oxidation
Examples: flaming, incinerators, hot-air sterilization
List the 2 goals of pasteurization.
Safety: kills pathogens
Extend shelf life of product/reduces spoilage
Compare pasteurization (classic and HTST) to UHT. What is accomplished by UHT that is not accomplished by either pasteurization method.
Classic: 63oC for 30 min, does not sterilize
High temp, short time (HTST): 72oC for 15 seconds, does not sterilize
Ultra high temp (UHT): 140oC for less than 1 second. Sterilizes but does not affect texture and flavor of food.
Define (equivalent treatments) and provide 2 examples.
Equivalent treatment is when different treatments have the same effect on controlling microbial growth
Example: hot air treatment, 170oC for 2 hours has the same sterilization effect as autoclave at 121oC for 15 min
Describe how filtration, low temperatures, high pressure, desiccation, and osmotic pressure suppress microbial growth.
Filtration: air or fluid passes through a filter and pathogens are trapped. Filters come in different pore sizes.
Air: HEPA filter. Removes microbes >.3 microns. Often used in hospital setting.
Liquid: membrane filtration removes microbes >.22 microns. Used on heat-sensitive liquids.
Low temperature: inhibits microbial growth (bacteriostatic, does not kill). Refrig, freezer.
High pressure: denatures proteins without heat
Osmotic pressure: low osmotic pressure causes plasmolysis of bacterial cells. Example, salting meats
Dessication: drying out, prevents metabolism. Example, raisins
Explain how radiation (ionizing radiation, as well as UV radiation) kills cells.
Ionizing radiation: x-rays, gamma rays, electron beams
Damages DNA: breaks phophodiester bonds
Used on lab and hospital supplies
Hamburger, spices, some vegetables
Non-ionizing radiation: UV
Damages DNA
Sterilizing air and surfaces in hospitals, “pasteurize” cider.
Disadvantage: does not penetrate, can only sterilize surfaces.
Microwaves
Kill by heat, not really antimicrobial
List appropriate applications of ionizing and UV radiation for sterilization. (see question 9)
List the factors related to effective disinfection.
Concentration of disinfectant: more isn’t always better, some need water added to work
Organic matter: have to clean the item off before disinfecting pH Time: how long disinfecting product is in contact with contaminated surface
Interpret the results of use-dilution tests and the disk-diffusion method.
Disk diffusion: measure the zone of inhibition. The larger the zone, the better the disinfecting agent worked. You can look up the “accepted” sizes of the zone of inhibition for different bacteria to determine which are good to use
Use-dilution: method of determining the effectiveness of a disinfectant using serial dilutions. A bacteria is exposed to disinfectant then is cultured. The effectiveness of the disinfectant is determined by the number of cultures that grow after being exposed to disinfectant. Identify the methods of action and preferred uses of chemical disinfectants. **CHART PAGE 201-202***
Phenols & phenolics: disrupt plasma membrane. Used by Lister to control infection in operating rooms
Bisphenols: disrupt plasma membranes. Phisohex, triclosan
Biguanides: disrupt plasma membrane. Chlorhexidine- skin antisepsis before surgery. Perioguard, hibiclens.
Halogens:
iodophors (betadine, povidone iodine)- surgical scrub, skin prep, ANTISEPTIC
Chlorine: bleach, chloramine, chlorine dioxide gas
Alcohols: denature proteins, dissolve lipids. Require water. Hand sanitizers
Heavy metals: Ag, Hg, Cu.
Silver: neonatal gonohhreal opthalamia, burn cream
Copper: algicide
Oligodynamic action: very tiny amounts are effective
Surfactants (detergents)- quaternary ammonium compounds (quats) denature proteins, disrupt plasma membrane both antiseptics (mouthwash) and disinfectants (Lysol, clorox, cavicide)
Chemical food preservatives
Organic acids: inhibit metabolism, controls molds and bacteria in foods & cosmetics. Benzoic acid, etc.
Nitrite: prevents endospore germination. Prevents botulism in sausage, etc
Antibiotics: natamycin prevents spoilage in cheese
Aldehydes: inactivate proteins by cross-linking with functional groups
**Medical equipment use:
Glutaraldehyde (CIDEX). Will STERILIZE. Virucidal in 10 mins, sporicidal in 3-10 hours
Gaseous sterilants: ethylene oxide
Denatures proteins
Use on heat sensitive materials (plastics). Very penetrating. Can sterilize medical equip through package.
Will STERILIZE
Uses: medical supplies/equipment, plastic ware, sutures, implanted prosthetics, large equipment
Plasma (gas): newer. Free radicals destroy microbes. Used on tubular instruments (endoscopy equip)
Super critical fluids: CO2 with gaseous and liquid properties (under pressure). Used for medical implants (heart valves, organs)
Peroxygens (oxidizing agents):
Ozone- water disinfection hydrogen peroxide- don’t use on wounds; for inanimate objects, contact lenses peracetic acid- STERILIANT
Differentiate halogens used as antiseptics from halogens used as disinfectants.
Antiseptics: iodophors
Disinfectants: bleach, etc
Identify the appropriate uses for surface-active agents (quats).
Antiseptic- mouthwash
Disinfectants- Lysol, Clorox, Cavicide
List the advantages of glutaraldehyde over other chemical disinfectants.
Will STERILIZE if given long enough exposure time
Identify chemical sterilizers.
Glutaraldehyde
Ethylene oxide
Peracetic acid
Describe appropriate applications of ethylene oxide sterilization.
Medical supplies/equipment, plastic ware, textiles, sutures, lensed instruments, implanted prosthetics, large pieces of equipment
Given an item requiring disinfection of sterilization, describe the most effective method/process to accomplish this.
Explain how the type of microbe affects the control of microbial growth.
Different microbes are resistant to different methods of control.
Illustrate the hierarchy of microorganisms from those easiest to destroy to those most difficult to destroy
These are the problem microorganisms
Chapter 14
Differentiate between infection and disease and provide examples of related processes.
Infection is the invasion or colonization of the body by pathogenic microorganisms; disease occurs when an infection results in any change from a state of health.
Disease is an abnormal state in which part or all of the body is not properly adjusted or incapable of performing its normal functions. An infection may exist in the absence of detectable disease. For example, the body may be infected with the virus that causes AIDS but experience no symptoms of the disease.
The presence of a particular type of microorganism in a part of the body where it is not normally found is also called an infection-and may lead to disease. For example, although large numbers of E. coli are normally present in the healthy intestine, their infection of the urinary tract usually results in disease.
Define symbiosis and list and describe the three types of symbiosis. Relate these types of symbiosis to the microorganisms that live in and on our bodies.
The relationship between the normal microbiota and the host is called symbiosis, a relationship between two organisms in which at least one organism is dependent on the other.
3 types of SYMBIOSIS-
Commensalism: one organism benefits, and the other is unaffected. For example, Staphylococcus epidermis on the skin. These bacteria live on secretions and sloughed-off cells, and they bring no apparent benefit or harm to the host.
Mutualism: Both organisms benefit. For example, the large intestine contains bacteria, such as E. coli, that synthesize vitamin K and some B vitamins. These vitamin are absorbed into the bloodstream and distributed for use by body cells. In exchange, the large intestine provides nutrients used by the bacteria, resulting in their survival.
Parasitism: One organism benefits at the expense of the other. Many disease-causing bacteria are parasites. For example, H1N1 virus particles benefit by deriving nutrients at the expense of the host cells.
Define opportunist.
Opportunistic pathogens—those that take advantage of certain situations—such as bacterial, viral, fungal or protozoan infections that usually do not cause disease in a healthy host, one with a healthy immune system. For example, microbes that gain access through broken skin or mucous membranes can cause opportunistic infections. Or, if the host is already weakened or compromised by infection, microbes that are usually harmless can cause disease (AIDS and Pneumocystis pneumonia)
Differentiate between communicable disease and noncommunicable disease and give an example of each.
Communicable disease refers to diseases that can pass from one person to another. For example, Chickenpox, measles and genital herpes.
Non-communicable diseases occur in one person and cannot be passed on to another person. These diseases are caused by microorganisms that normally inhabit the body and only occasionally produce disease. An example is tetanus: Clostridium tetani produces disease only when it is introduced into the body via abrasions.
Communicable diseases are also known as infectious diseases, and non-communicable diseases are referred to as chronic.
Define endemic, epidemic, and pandemic and give an example of each.
Endemic disease- A disease constantly present in a population; an example of such is the common cold.
Epidemic disease- If many people in a given area acquire a certain disease in a relatively short period; influenza is an example of a disease that often achieves epidemic status.
Pandemic disease- An epidemic disease that occurs worldwide. Influenza as well as AIDS are examples.
Differentiate between acute, chronic, and latent infections.
Acute- one that develops rapidly but lasts only a short time; i.e. Influenza
Chronic- develops more slowly, and the body’s reactions may be less severe, but the disease is likely to continue or reoccur for long periods. i.e. hepatitis B
Latent- one in which the causative agent remains inactive for a time but then becomes active to produce symptoms of the disease. i.e. shingles
Differentiate between local and systemic infections.
Local Infection- One in which the invading microorganisms are limited to a relatively small area of the body. Some examples of local infections are boils and abscesses.
Systemic Infection- Microorganisms or their products are spread throughout the body by the blood or lymph. Measles is an example of a systemic infection.
Differentiate between bacteremia and septicemia.
Bacteremia refers to a bacterial invasion into blood circulation. Bacteremia can occur when you brush your teeth, pick a scab, or squeeze a zit. Bacteremia may also result from any type of dental or surgical procedure. Bacteremia may or may not cause any symptoms, depending on whether the organism was able to replicate themselves in the blood stream. For most people, the immune system should "notice" the organisms immediately and respond with specialized white blood cells to search out and destroy them. Of course, it is possible for bacteremia to progress to septicemia, especially if an individual has a weakened immune system.
Septicemia, also called blood poisoning, is a systemic infection arising from the multiplication of pathogens in the blood. This is an infection that moves rapidly and is life-threatening. Simply put, septicemia is bacteremia with replicating bacteria to cause an infection. Septicemia is a common example of sepsis (a toxic inflammatory condition arising from the spread of microbes)
Differentiate between primary infection and secondary infection.
Primary infection- an acute infection that causes the initial illness.
Secondary infection- one caused by an opportunistic pathogen after the primary infection has weakened the body’s defenses. Secondary infections of the skin and respiratory tract are common and are sometimes more dangerous than the primary infections.
List the sequence of events in the development of an infectious disease.
Incubation Period- Time between infection and onset of signs and/or symptoms.
Prodromal Period- Short time of generalized, mild symptoms preceding illness. Symptoms often include malaise and muscle aches. Not all infectious diseases have a prodromal period Period of Illness- Most severe stage of an infectious disease. Signs and symptoms are most evident at this time. Patient’s immune system has not yet fully responded. Pathogen is harming the body and causing disease. A physician typically sees the patient during this stage
Period of Decline-
Body gradually returns to a normal state of health.
Immune response and/or medical treatment begin to affect the growth and survival of the pathogen. Signs and symptoms subside. The immune response and antibody titers normally peak during this stage of infectious disease. If the patient does not recover, the disease may be fatal.
Period of Convalescence-
This is a period of recovery Damaged tissues and other body systems are repaired
Define reservoir, zoonosis, vector, and carrier, and give examples.
Reservoir- Sites were pathogens persist and go on to cause other infections are termed reservoirs of infection.
Zoonosis- a disease that occurs primarily in wild and domestic animals but can be transmitted to humans.
Vector- An arthropod that carries disease-causing organisms from one host to another.
Carrier- Organism (usually refers to humans) that harbors pathogens and transmits them to others.
List modes of transmission of infectious diseases.
Contact transmission is the spread of an agent of disease by direct contact, indirect contact or droplet transmission.
Direct contact- also known as person-to-person transmission, is the direct transmission of an agent by physical contact between its source and a susceptible host.
Indirect contact- occurs when the agent of disease is transmitted from its reservoir to a susceptible host by means of a nonliving object.
Droplet transmission- microbes are spread in mucous droplets that travel only short distances. These droplets are discharged into the air by coughing, sneezing or talking. (travel less than 1 meter)
Vehicle Transmission is the transmission of disease agents by a medium, such as water, food or air.
Waterborne transmission- pathogens are usually spread by water contaminated with untreated or poorly treated sewage. Airborne transmission- the spread of agents of infection by droplet nuclei in dust that travel more than 1 meter from reservoir to host.
Vectors- (An arthropod that carries disease-causing organisms from one host to another)
Mechanical transmission- the passive transport of the pathogens on the insect’s feet or body parts.
Biological transmission is an active process and is more complex. The arthropod bites an infected person or animal and ingests some of the infected blood.
Define and give an example of a fomite.
A fomite is a nonliving object that can spread infection (a towel, money, clothing or dishes)
Define nosocomial infection, list three common microorganisms recovered from nosocomial infections, and list the most common body sites of nosocomial infections.
A nosocomial infection does not show any evidence of being present or incubating at the time of admission to a hospital; it is required as a result of a hospital stay. (8th leasing cause of death in the U.S.)
Three common microorganisms recovered from nosocomial infections are:
Coagulase-negative staphylococci- 15% of total infections, 89% resistant to Antibiotics, most common cause of sepsis.
Staphylococcus aureus- 15% of total infections, 50% resistant to Antibiotics, most frequent cause of pneumonia.
Enterococcus spp.- 10% of total infections, 4-71% resistant to Antibiotics, most common cause of surgical wound infections.
Principal sites of nonsocial infections:
Urinary tract infections
Surgical site infections
Lower respiratory infections
Bacteremia, caused primarily by IV catheterizations
Describe what is meant by the term “compromised”. State the factors might cause a person to become compromised.
A compromised host is one whose resistance to infection is impaired by disease, therapy or burns. Two principal conditions can comprise the host; broken skin or mucous membranes, and a suppressed immune system.
List several ways in which nosocomial infections are transmitted.
Direct contact transmission from hospital staff to patient and from patient to patient.
Indirect contact transmission through fomites and the hospital’s ventilation system (airborne transmission)
Define epidemiology and state the contributions of Snow, Semmelweis, and Florence Nightingale.
Epidemiology- The science that studies when and where diseases occur and how they are transmitted.
John Snow (15 March 1813 – 16 June 1858) was an English physician and a leader in the adoption of anesthesia and medical hygiene. He is considered one of the fathers of modern epidemiology in part because of his work in tracing the source of a cholera outbreak in Soho, London, in 1854.
Ignaz Philipp Semmelweis(July 1, 1818 – August 13, 1865) was a Hungarian physician of German descent now known as an early pioneer of antiseptic procedures. Described as the "savior of mothers", Semmelweis discovered that the incidence of puerperal fever could be drastically cut by the use of hand disinfection in obstetrical clinics.
Florence Nightingale (May 12, 1820 – August 13, 1910) was a celebrated British social reformer and statistician, and the founder of modern nursing. She came to prominence while serving as a nurse during the Crimean war, where she tended to wounded soldiers. She recorded statistics on epidemic typhus in the English civilian and military populations. In 1858, she published a thousand-page report using statistical comparisons to demonstrate that diseases, poor food, and unsanitary conditions were killing
soldiers.
Synercid- Quinupristin/dalfopristin (trade name Synercid) is a combination of two antibiotics used to treat infections by staphylococci and by vancomycin-resistant Enterococcus faecium.
Linezolid is a synthetic antibiotic developed by a team at Pharmacia and Upjohn Company. It is used for the treatment of serious infections caused by Gram-positive bacteria that are resistant to several other antibiotics.
Chapter 20
Identify the contributions of Paul Ehrlich and Alexander Fleming to chemotherapy.
Ehrlich- Early 20 century, coined the term chemotherapy, speculated on the magic bullet to selectively find and destroy pathogens but not harm the host.
Fleming- Discovered Penicillin in 1928, produced by Penicillium
Name the microbes that produce most antibiotics.
Streptomyces/Actinomycetes- produce more than half, found in soil
Gram-Positive Rods- Bacillus/Paenibacillus polymyxa- endospore forming bacteria
Fungi/Mold- Cephalosporium/Penicillium
Describe the problems of chemotherapy for viral, fungal, protozoan, and helminthic infections.
Viral- the pathogen is within human hosts cells and the genetic information of the virus is directing human cells to make viruses rather than synthesize normal cell material
Fungal-Protozoan-Helminthic infections- the pathogen is a eukaryotic cell. These cells closely resemble human cells and choices of drugs are much more limited.
Define the following terms: spectrum of activity, broad-spectrum antibiotic, superinfection
Spectrum of activity- defines the range of pathogens which are sensitive to an infection
Broad spectrum antibiotics- Antibiotics that affect a broad range of gram-positive or gram negative bacteria= Ampicillin
Narrow spectrum antibiotics- Antibiotics that affect a small range of microbial types= Penicillin G, affects gram-positive bacteria but very few gram-negative
Superinfection- infection occurring after or on top of an earlier infection, esp. following treatment with broad-spectrum antibiotics. Also when growth of a target pathogen that has developed resistance to the antibiotic.
Describe how broad spectrum antibiotics may contribute to the development of superinfections.
Broad spectrum drugs destroy many normal microbiota of the host, normal microbiota ordinarily compete with and check the growth of pathogens, if the antibiotic doesn’t destroy certain organisms in the normal microbiota but does destroy their competitors, the survivors may flourish and become opportunistic pathogens. Ex Candida albicans, an overgrowth of yeast.
Identify five modes of action of antimicrobial drugs.
Inhibiting cell wall synthesis= interfere with peptidoglycan- penicilllins, cephalsoporins, bacitracin, vancomycin
Inhibition of protein synthesis= interfere with ribosomes- chlorampehenicol, erythromycin, tetracycline, streptomycin
Inhibition of nucleic acid replication and transcription= inhibits DNA or RNA synthesis- quinolones, fluoroquinolones, rifampin
Injury to plasma membrane= humans have this, hard to isolate- Polymixin B
Inhibition of essential metabolite synthesis/competitive inhibitor of enzymes- sulfanilamide, trimethoprim
Describe the mode of action of the following antibiotics: penicillin (natural and semisynthetic)- Inhibitor of cell wall synthesis- susceptible to beta-lactamase cephalosporin- Inhibitor of cell wall synthesis- susceptible to beta-lactamase, differ in spectrum and route of administration. Many generations, each slightly different vancomycin- Inhibitor of cell wall synthesis, important “last line” against antibiotic resistant S. aureus (MRSA) aminoglycosides- Inhibitor of Protein Synthesis(Streptomycin, Neomycin, Gentamycin) tetracycline- Inhibitor of protein synthesis, broad spectrum-concerns with developing teeth chloramphenicol- Inhibitor Protein Synthesis, broad spectrum, concerns can cause bone marrow production to shut down, toxic erythromycin- Inhibitor of protein synthesis- narrow spectrum sulfonamides- Competitive Inhibitor of enzymes, inhibit folic acid synthesis trimethoprim-sulfamethoxazole= Comptetive inhibitor of enzymes ex Bactrim, Septra rifampin- Inhibitor of nucleic acid synthesis, inhibits RNA synthesis ciprofloxacin- Inhibitor of nucleic acid synthesis, inhibits DNA gyrase synercid- Inhibitor of protein synthesis- used against MRSA, VRE linezolid- Inhibitor of protein synthesis- used against MRSA and VRE- Vancomycin Resistant Enterococcus Name the two major advantages of semisynthetic penicillin and identify two different semisynthetic “cillins” and which advantage they illustrate.
Semisynthetic=partly produced by mold, part added synthetically-
Extended spectrum- developed to overcome the problem of narrow spectrum of natural penicillins. Effective against many gram-negative and gram-positive bacteria. Ex ampicillin, amoxacillin
Penicillinase resistant- an enzyme produced by some bacteria that actively destroy penicillin, these penicilllins are not damaged by this enzyme. Ex Oxacillin and Methicillin
Not mutually exclusive!
Name two antimycobacterial agents and describe how these drugs act selectively against mycobacteria.
Isoniazid (INH) –inhibits mycolic acid synthesis
Ethambutol- Inhibits incorporation of mycolic acid
Used against TB!!! Rifamycin/Rifampin also used against TB
Describe how sulfa drugs inhibit microbial growth.(Competitive Inhibitors of Enzymes)
Inhibit folic acid synthesis (humans don’t make folic acid), broad spectrum, some people develop allergies
Describe significant side effects of the following antimicrobials:
Aminoglycosides (gentamicin, tobramycin, amikacin) - Used against Pseudomonas aeruginosa. Can develop ototoxicity- 8th cranial nerve and nephrotoxicity- in the kidneys, must be monitored
Tetracycline- Concerns over discoloration of teeth. Not given to pregnant women( can also cause liver problems in pregnant women) or kids under 12
Ciprofloxacin- can damage developing cartilage
Chloramphenicol- Suppresses bone marrow activity which affects the formation of blood cells, can not be given for long periods of time.
Briefly explain the modes of action of currently used antifungal drugs.
Eukaryotes such as fungi use the same mechanisms to synthesize proteins and nucleic acids as humans. Inhibition of ergosterol synthesis (fungal cell membrane, plasma membrane) Polyenes- Amphotericin B
Azoles- Miconazole, Triazoles Inhibition of cell wall synthesis- Cancidas is used against Candida and Pneumocystitis Ex. Echinocandins Inhibition of nucleic acid synthesis- Flucytocine, Diflucan Other anitfungals- Griseofulvin- affective against fungal infections in hair and nails Tolnaftate- alternative to miconazole, topical Pentamidine- used for Pneumocystis pneumonia Explain the modes of action of currently used antiviral drugs.
Nucleoside and Nucleotide Analogs- Acyclovir Famciclovir Ganciclovir Valciclovir Ribavirin Interferons-Cells infected by a virus produce interferon, which inhibits the spread of infection. “Paul Revere” proteins, messengers, Tweeters Alpha interferon- treats viral hepatitis Imiquimod- stimulates the production of interferons Enzyme inhibitors/Inhibit neuraminidase- to treat influenza Zanamivir (Relenza) Oseltamivir(Tamiflu) Inhibit uncoating- to treat influenza Amantadine Drugs for HIV Protease inhibitors- indinavir Integrase inhibitors- Fusion inhibitors Entry inhibitors Describe two tests for microbial susceptibility to chemotherapeutic agents, including one qualitative method and one quantitative method.
Diffusion methods-
Disc-Diffusion Method/ Kirby-Bauer test = Qualitative method- If the agent is effective a zone of inhibition forms around the disc, this can be measured and reported as, Sensitive, Intermediate, Resistant Results are inadequate, but it is simple and inexpensive
The E test- enables an estimate of the minimal inhibitory concentration (MIC) = the lowest antibiotic concentration that prevents visible bacterial growth. Broth dilution test- Quantitative To determine MIC and MBC- minimal bactericidal concentration
Describe the mechanisms of drug resistance (the concept map will help with this) Describe an R plasmid (Resistance Factor) and state how it contributes to the spread of antimicrobial resistance. Describe the problems in treating infections due to MDR-TB and XDR-TB, MRSA, VRSA, and VRE
Mutations lead to antibiotic resistance
Antibiotics are NOT mutagenic- do not cause mutations
4 ways of resistance
Blocking entry- altered porins
Inactivating enzymes, ex Beta lactamase
Alteration of target molecule- prevents binding of antibiotic
Efflux of antibiotic (pumps)- Membrane pumps/resistance pumps
Mutations are spread Horizontally
Conjugation
Transduction Vertically
Cell division
R plasmid (Resistance Factor)
Resistance is carried by plasmids which can jump from one piece of DNA to another
R plasmids can be transferred between bacterial cells in a population and between bacterial populations
MDR-TB and XDR-TB= Mycobacterium tuberculosis
ORSA/MRSA= Oxacillin/Methicillin Resistant Staphylococcus aureus
Vancomycin is reserved for these
Now VRSA-Vancomycin Resistant Staphylococcus aureus= treated with Synercid/Linezolid
VRE- Vancymycin Resistant Enterococcus- treated with Synercid/Linezolid
CRE/CRK- Carbepenam resistant
Describe some of the problems resulting from heavy overuse of antibiotics and include in this description the problem of use of antibiotics in livestock feeds.
Heavy overuse of antibiotics leads to resistance Using outdated or weakened antibiotics Using antibiotics for a cold Failing to complete the prescribed regimen Using someone else’s prescription
Using antibiotics in animal feed
Causing a “survival of the fittest” antibiotics kill some bacteria but other bacteria have properties that help them survive Resistance to antimicrobial drugs results in mutations, these mutations are transferred FQ- Fluoroquinolone resistant C. jejuni in humans emerged in 1990s
Not in review-
Antimicrobial drugs- interfere with the growth of microbes within a host
Antibiotics- a substance produced by a microbe that in small amounts inhibits another microbe
Selective toxicity- a drug that kills harmful microbes without damaging the host
Bactericidal- kill microbes directly
Bacteriostatic- prevents microbes from growing
Synergism- when the effect of 2 drugs together is greater than the effect of either one alone
Antagonism- when the effect of 2 drugs together is less than the effect of either one alone
Future of chemotherapeutic agents Antimicrobial peptides Broad spectrum antibiotics Nisin- lactic acid bacteria Defensins- human
CHAPTER 15
Identify the principal portals of entry
Mucous membranes, skin and the parenteral route (beneath the skin or membranes)
Define ID50 and LD50
ID50 is the number of microorganisms that will infect 50% of the population. LD50 is the amount of toxin needed to be lethal to 50% of the population
Using examples, explain how microbes adhere to host cells
The attachment between pathogen and host is accomplished by means of surface molecules on the pathogen called adhesins or ligands that bind specifically to complementary surface receptors on certain host tissue. Streptococcus mutans attaches to teeth surface via glycocalax. Escherichia coli use fimbriae to attach and Streptococcus pyogenes uses an M protein.
Describe how biofilms contribute to microbial virulence
Biofilms are resistant to antibiotic. Bacteria uses biofilms to attach, communicate and share nutrients.
Explain how capsules and cell wall components contribute to pathogenicity
Capsules resist the host’s defenses by impairing phagocytosis. The chemical nature of the capsule prevents the phagocytic cell from adhering to the bacterium. The capsule itself may be causative (S. pneumoniae). S. pyogenes produces a heat and acid resistant protein called M protein in the cell wall and surface. Capsules and biofilms resist phagocytosis and helps pathogens stick.
Compare the effects of coagulases, kinases, hyalaurinidase, and collagenase
Coagulase an enzyme that clots fibrinogen in the blood isolates bacteria by “walling off” areas in the body produced by S. aureus.
Kinase digests fibrin clots. There are 2 types Staphylokinase and Streptokinase.
Hyalurondiase is an enzyme secreted by Staph and Strep cocci. It hydrolyses hyaluronic acid which is a type of polysaccharide formed in the body. Can help diffuse meds.
Collagenase breaks down collagen by hydrolysis, produced by several species including Clostridium.
Define and give examples of antigenic variation
Antigenic variationis the mechanism by which a pathogen evades a host immune response by changing its surface proteins. It is adaptive; the most fit for the environment will survive and reproduce. N. gonorrhoeae has several copies of the Opa-encoding gene, resulting in cells with different antigens over time
Describe the function of siderophores
Siderphores are proteins that are secreted when a pathogen requires iron. They bind more steal the iron and make the iron-siderophore complex which is the delivered to the siderphore receptors on the surface of the bacteria
Provide an example of direct damage, and compare this to toxin production
Direct damage is very parasite like, the pathogen essentially takes over the host cell and consumes its nutrients and leaves its waste. The bacteria grow and may eventually lyse the cell. Most damage however is due to toxins which are poisonous substances that are produced by some microorganisms
Contrast the nature and effects of exotoxins and endotoxins
Exotoxins are proteins produced inside the bacteria and are mostly Gram positive. They are structure and or function specific. There are 3 types: A-B toxins, membrane disrupting and supreanitgens
Endotoxins are the lipid portion of lipopolysaccharides that are part of the outer membrane of the cell wall of gram-negative bacteria. The endotoxins are liberated when the bacteria die and the cell wall breaks apart
List 5 examples of exotoxins, including the organism that produces each and the effects of each specific exotoxin
Disease Bacteria Toxin Mechanism and effect
Botulism Clostridium difficile Botulinum A-B Neurotoxin prevents nerve impulse
Tetanus Clostridium tetani Tetanospasmin A-B Neurotoxin blocks nerve impulses to muscle relaxation pathway
Diptheria Corynebacterium diphtheria A-B Cytotoxin inhibits protein synthesis in nerve, heart and kidney
Antibiotic associated Clostridium membrane- enterotoxin causes
Diarrhea difficile disrupting secretion of fluids and electrolytes, result in diarrhea. Cytotoxin disrupts host cytoskeleton
Toxic shock Staph .aureus Superantigen Toxin causes secretion of fluids and electrolytes from capillaries that reduce blood vol. and lower blood pressure
List 9 cytopathic effects of viral infections
During multiplication cytocidal viruses cause the macromolecular synthesis w/in the cell host to stop
Virus causes hosts lysozomes to release their enzymes resulting in destruction of intracellular contents and host cell death
Inclusions in nucleus from Papovavirus and Adenovirus. Inclusions in cytoplasm from Rhabdovirus. Inclusions in both from Cytomegalovirus.
Viruses may cause cells to form a very large multi-nucleated cell called a synctium. From measles mumps and the common cold
May reduce cells ability to fight infection by prompting cells to reduce production of immune substance
Viral infections prompt host cell DNA to code for interferons
Viral infections can induce antigenic changes on the host cell surface. These antigenic changes elicit a host antibody response against the infected cell
Viral infections can change host chromosomes, oncogenes may be added causing cancer
Cancer causing viruses inhibit “contact inhibition” between host cells thus promoting cancer
Differentiate portals of entry and portals of exit
Portals of entry are where microorganisms enter the body, some examples are respiratory tract, gastrointestinal tract, genitourinary tract, conjunctiva, skin and the parenteral route. Portals of exit are where microorganisms exit the body and are generally the same places as entry.