normal microbial flora

Question 1

name some normal aerobic/facultative mouth flora

Answer 1

• viridans streptococci
• neisseria
• diphtheroids (corynebacterium)
• Staph epidermidis

Question 2

what are some important reasons for normal flora?

Answer 2

• 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

Question 3

viridans streptococci #s

Answer 3

10^6 - most prevalent bacteria in mouth

Question 4

viridans streptococci are the most common cause of:

Answer 4

subacute bacterial endocarditis

Question 5

what is dextran?

Answer 5

polysaccharide product from sugar digestion by V. streptococci. ingredient in dental plaque

Question 6

viridans strepcocci - shape and gram stain

Answer 6

gram positive cocci

Question 7

neisseria - shape and gram stain

Answer 7

gram negative diplococci

Question 8

neisseria #s

Answer 8

second most prevalent in mouth

Question 9

neisseria can cause:

Answer 9

N. meningitides can cause meningitis - rare

Question 10

what are diphtheroids?

Answer 10

corynebacterium species which are not C. diphtheriae

Question 11

diphtheroids - shape and gram stain

Answer 11

pleomorphic gram positive rods

Question 12

S. epidermidis - shape and gram stain

Answer 12

gram positive cocci - grape clusters

Question 13

what are S. epidermidis and diphtheroids both known for?

Answer 13

They are the two most common contaminants of blood cultures

Question 14

Eikenella corrodens?

Answer 14

normal mouth flora associated with human bites and clenched fist injuries

Question 15

name some normal anaerobic mouth flora

Answer 15

• fusobacterium
• prevotella
• anaerobic streptococci
• actinomyces

Question 16

what part of the upper resp/GI tract is not affected by anaerobic flora?

Answer 16

lower trachea - anaerobic bacteria do not extend there and it is virtually bacteria free

Question 17

explain aspiration pneumonia:

Answer 17

• aspiration of own oral secretion

- offending pathogens are combination of normal mouth flora (mixed aerobes and anaerobes)

Question 18

is penicillin useful against infections caused by mouth flora?

Answer 18

generally yes, most are sensitive to penicillin

Question 19

under what circumstances can bacteria flourish in the stomach?

Answer 19

• gastic achlorhydia (no stomach acid)

- gastric obstruction

Question 20

why is the upper small intestine generally sterile?

Answer 20

• peristalsis

- unconjugated bile acids

Question 21

when is disease possible in upper small intestine?

Answer 21

• anatomical alterations that effect peristalsis such as gastric bypass surgery

Question 22

why is there bacterial proliferation in terminal ileum and large intestine?

Answer 22

greater stasis

Question 23

name 7 flora present in most large intestines/feces

Answer 23

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

Question 24

infant intestinal flora:

Answer 24

• fetal intestine is sterile
• breast-fed - primarily bifidobacterium
• weaning/bottle fed - like adult flora

Question 25

normal flora of skin:

Answer 25

• staph epidermidis
• staph aureus
• diphtheroids
• anaerobes such as proprionibacterium and peptococcus

Question 26

normal upper respiratory tract flora:

Answer 26

• nose: staph aureus
• throat: viridan streptococci, neisseria, staph epidermidis
• anaerobes: bacteroides, fusobacterium, costridium, peptostreptococcus

Question 27

vaginal flora

Answer 27

• 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