Normal Microbial Flora Flashcards
What are the Important Contributions of Microbiota?
1a. PROTECTIVE
- decrease pathogen colonization
1b. BUT, can cause disease (esp in immunocompromised)
2a. NUTRITIONAL
- provide B and K vitamins
2b. BUT overgrowth can lead to fat malabsorption and vitamin deficiency
What are the common aerobic MOUTH flora?
V. Streptococci
Neisseria
Diptheroids
S. Epidermidis
(Strep, Staph, and diplococci)
What’s the predominant mouth organism?
V. Streptococci
106 per ml saliva
Positive cocci chains
What does oral Strep thrive on?
Sugar, obvs,
Sucrose -> plaque
Lactic acid byproduct causes cavities
What’s the second most common mouth organism?
Non pathogenic Neisseria
NOT meningitidis (which can colonize throat but is a pathogen)
How can you tell it’s Neisseria?
Gram negative diplococci
What’s a common cause of blood culture contaminant?
Diptheroids/Corynebacterium
Colonize skin
Also mouth
Gram positive
Most common contaminant of blood cultures in presence of foreign body?
Staph Epidermidis
Gram positive grapes
coagulate negative
Why shouldn’t you bite people?
Eikenella Corrodens
Gram negative rod normally found in mouth
BUT
Can cause skin and soft tissue infections
What are the normal anaerobes in the mouth?
Fusobacterium -rod
Prevotella -rod
Peptostrep +cocci
Actinomyces
oral flora diseases and treatments
Periodontal infections
Aspiration pneumonia
Most sensitive to penicillin
What’s most common cause of subacute bacterial endocarditis?
V. Strep
What’s normally found in the stomach?
NOTHING
Ha, too much acid
Bacteria can proliferate in Gastric Achlorhydria or gastric obstruction
Who usually colonizes upper small intestine?
Generally no one in fasting individual
- Fast movement through
- Unconjugated bile = killer
Ok the, what about the terminal ileum?
Usually less than 106 per ml
Resembles stool biota
Coliforms and anaerobes (B. Fragilis)
The juicy stuff: What does the colon and feces look like?
Bacterial proliferation (1000 per gram of wet feces)
Stasis and better pH
Predominantly ANAEROBES
Most common organism in colon and feces?
BACTEROIDES (Fragilis)
Gram- anaerobic rods
*What’s the important metabolic activity of bacteroides?
Generate:
ammonia,
acid,
gas
Ammonia formed by splitting urea and proteins
How would you treat abdominal infections?
DON”T USE PENICILLIN
Fragilis is resistant
Clindamycin
Cefoxitin
Metronidazole
+
Aminoglycoside
What are the lesser known colonizers of bowel?
Bifidobacterium
- not pathogenic
- sensitive to Penicilin
- common in breast fed infants
Lactobacillus
Clostridium
Coliforms (enteric gram negative rods)
-e. Coli
How do bacteria and bile interact?
Bacteria turn conjugated bile acids -> free bile acids
Conjugated bile acids necessary for fat absorption
-> Overgrowth in small intestine leads to malabsorption
Bacteria and ammonia?
Bacterial degradation in colon
-> inc blood ammonia levels
Liver tries to bring back down
What happens to Carbs in the gut?
Those not absorbed are fermented by intestinal flora
-> pH drop
Good for local flora, Keeps out pathogens
Which bacteria are usually found on the skin?
Staph Epidermidis
Staph Aureus
Diptheroids
Anaerobes
What’s the most common skin organism?
S. Epidermidis
Generally non pathogenic
-EXCEPT with foreign bodies
