normal microbial flora Flashcards
name some normal aerobic/facultative mouth flora
- viridans streptococci
- neisseria
- diphtheroids (corynebacterium)
- Staph epidermidis
what are some important reasons for normal flora?
- protective host defense mechanism by interfering with colonization of pathogenic bacteria
- nutritional function, produce B12 and vitamin K
- bacterial overgrowth in small intestine can lead to fat malabsorption and B12 deficiency
viridans streptococci #s
10^6 - most prevalent bacteria in mouth
viridans streptococci are the most common cause of:
subacute bacterial endocarditis
what is dextran?
polysaccharide product from sugar digestion by V. streptococci. ingredient in dental plaque
viridans strepcocci - shape and gram stain
gram positive cocci
neisseria - shape and gram stain
gram negative diplococci
neisseria #s
second most prevalent in mouth
neisseria can cause:
N. meningitides can cause meningitis - rare
what are diphtheroids?
corynebacterium species which are not C. diphtheriae
diphtheroids - shape and gram stain
pleomorphic gram positive rods
S. epidermidis - shape and gram stain
gram positive cocci - grape clusters
what are S. epidermidis and diphtheroids both known for?
They are the two most common contaminants of blood cultures
Eikenella corrodens?
normal mouth flora associated with human bites and clenched fist injuries
name some normal anaerobic mouth flora
- fusobacterium
- prevotella
- anaerobic streptococci
- actinomyces
what part of the upper resp/GI tract is not affected by anaerobic flora?
lower trachea - anaerobic bacteria do not extend there and it is virtually bacteria free
explain aspiration pneumonia:
- aspiration of own oral secretion
- offending pathogens are combination of normal mouth flora (mixed aerobes and anaerobes)
is penicillin useful against infections caused by mouth flora?
generally yes, most are sensitive to penicillin
under what circumstances can bacteria flourish in the stomach?
- gastic achlorhydia (no stomach acid)
- gastric obstruction
why is the upper small intestine generally sterile?
- peristalsis
- unconjugated bile acids
when is disease possible in upper small intestine?
- anatomical alterations that effect peristalsis such as gastric bypass surgery
why is there bacterial proliferation in terminal ileum and large intestine?
greater stasis
name 7 flora present in most large intestines/feces
1) bacteroides fragilis
2) bifidobacterium - non-pathogenic
3) loctobacilli
4) clostridial species
5) coliforms and enterococcus (aerobes)
6) other anaerobes
7) S. aureus, pseudomonas, proteus, kebsiella
infant intestinal flora:
- fetal intestine is sterile
- breast-fed - primarily bifidobacterium
- weaning/bottle fed - like adult flora
normal flora of skin:
- staph epidermidis
- staph aureus
- diphtheroids
- anaerobes such as proprionibacterium and peptococcus
normal upper respiratory tract flora:
- nose: staph aureus
- throat: viridan streptococci, neisseria, staph epidermidis
- anaerobes: bacteroides, fusobacterium, costridium, peptostreptococcus
vaginal flora
- lactobacillus - maintains low pH
- E coli - from fecal matter, UTIs and occasionally sepsis
- 15-20% have group B strep, possible sepsis in newborn through birth canal
