normal flora microbiology

Intro to Microbiology:
Gram stain:

Gram +
Gram -

Exotoxin
Except Listeria has endotoxin
Endotoxin
Except
Capsules
Strep pneumo
VERY Dangerous:
(Some Strange Killers Have Pretty Nice Capsules)
1. Salmonella
2. Strep
3. Kleibsiella
4. Hemophilus B
5. Pseudomonas
6. Nisseria-(largest capsule- most likely cause of any toxicity)
7. Citroacter

Gram (+) Gram (-)

N-acetyl muramic acid (Nam) +
N-acetyl glucosamine (Nag) = Peptidoglycan wall
Contains Techtoic Acid → non-toxic

Steps for Gram stain
1. Crystal violet → picked up by gram (+) by peptidoglycan
2. Iodine (sealant) seal the color in
a. Too little won’t adhere to G+
b. Too much might stain G-
3. Wash excess crystal violet with EtOH
4. Sapphrine (pink/red to stain G-)

Endotoxin(Periplasmic Space – contains endotoxin)
Lipoopolysaccharides means (lipid (A) and sugar-(0-antigensaccharides) and the core antigen is variable
Once u give antibiotic the condition get worse because endotoxin release cause (inflammation) so in pedriatic pretreat with steroid ( board exam) Destroying outer membrane will first release Lipid A causing pt to get worse before getting better
-Severe shock  Gram negative sepsis. pediatrics- give steroids before antibiotics for bacterial meningitis (dexamethasone BEFORE antibiotics) to keep inflammation down and prevent hearing loss and neuropathies.

Acid Fast Stain:
For Mycolic Acid
Mycobacteria
Nocardia is partially acid fast and Gram +
Cryptosporidium is protozoa that is partially acid fast.
Only the pathogen will be pink, everything else will be blue.

NORMAL FLORA

Gram + or Gram - ??
If the part of the body that is affected is EXPOSED TO O2 → Gram + Aerobe
But if Hiding from O2 → Gram + Anaerobe
If part of the body that is affected is NOT EXPOSED TO O2 → Gram – Anaerobe
If in both locations with or without O2 → Facultative
Facultative Anaerobe prefers no O2
Facultative Aerobe