Introduction to Microbiology
Foundations in MicrobiologySeventh Edition
13.1 We Are Not Alone
The human body exists in a state of dynamic equilibrium
Many interactions between human body and microorganisms involve the development of biofilms
Colonization of the body involves a constant “give and take”
Contact, Colonization, Infection, Disease
Microbes that engage in mutual or commensal associations – normal (resident) flora , indigenous flora, microbiota
Infection – a condition in which pathogenic microbes penetrate host defenses, enter tissues, and multiply
Pathogen – infectious agent
Infectious disease – an infection that causes damage or disruption to tissues and organs
Resident Flora
Most areas of the body in contact with the outside environment harbor resident microbes
Internal organs, tissues, and fluids are microbe-free
Transients – microbes that occupy the body for only short periods
Residents – microbes that become established
Resident Flora
Bacterial flora benefit host by preventing overgrowth of harmful microbes – microbial antagonism
Endogenous infections – occur when normal flora is introduced to a site that was previously sterile
Initial Colonization of the Newborn
Uterus and contents are normally sterile and remain so until just before birth
Breaking of fetal membrane exposes the infant; all subsequent handling and feeding continue to introduce what will be normal flora
Flora of the Human Skin
Skin is the largest and most accessible organ
Two cutaneous populations
Transients: influenced by hygiene
Resident: stable, predictable, less influenced by hygiene
Flora of the Gastrointestinal Tract
GI tract is a long hollow tube, bounded by mucous membranes
Tube is exposed to the environment
Variations in flora distribution due to shifting conditions (pH, oxygen tension, anatomy)
Oral cavity, large intestine, and rectum harbor appreciable flora
Flora of the Mouth
Most diverse and unique flora of the body
Numerous adaptive niches
13.1 We Are Not Alone
The human body exists in a state of dynamic equilibrium
Many interactions between human body and microorganisms involve the development of biofilms
Colonization of the body involves a constant “give and take”
Contact, Colonization, Infection, Disease
Microbes that engage in mutual or commensal associations – normal (resident) flora , indigenous flora, microbiota
Infection – a condition in which pathogenic microbes penetrate host defenses, enter tissues, and multiply
Pathogen – infectious agent
Infectious disease – an infection that causes damage or disruption to tissues and organs
Resident Flora
Most areas of the body in contact with the outside environment harbor resident microbes
Internal organs, tissues, and fluids are microbe-free
Transients – microbes that occupy the body for only short periods
Residents – microbes that become established
Resident Flora
Bacterial flora benefit host by preventing overgrowth of harmful microbes – microbial antagonism
Endogenous infections – occur when normal flora is introduced to a site that was previously sterile
Initial Colonization of the Newborn
Uterus and contents are normally sterile and remain so until just before birth
Breaking of fetal membrane exposes the infant; all subsequent handling and feeding continue to introduce what will be normal flora
Flora of the Human Skin
Skin is the largest and most accessible organ
Two cutaneous populations
Transients: influenced by hygiene
Resident: stable, predictable, less influenced by hygiene
Flora of the Gastrointestinal Tract
GI tract is a long hollow tube, bounded by mucous membranes
Tube is exposed to the environment
Variations in flora distribution due to shifting conditions (pH, oxygen tension, anatomy)
Oral cavity, large intestine, and rectum harbor appreciable flora
Flora of the Mouth
Most diverse and unique flora of the body
Numerous adaptive niches