anaerobic infections and normal flora

Question 1

noticeable characteristics of most anaerobic infections:

Answer 1

• abscesses - from native flora
• foul-smelling discharge
• gas in necrotic tissue

Question 2

where do most anaerobic infections occur?

Answer 2

deep or necrotic tissue where the oxygen is low ( lack of oxidation-reduction potential) and access to endogenous local bacteria is available

Question 3

predisposing conditions for anaerobic infections:

Answer 3

• pulmonary aspiration
• bowel surgery
• poor dental hygiene
• abortion
• human or animal bites
• trauma
• malignancy

Question 4

do most anaerobic infections involve only one organism?

Answer 4

• no, in contrast to aerobic infections, most anaerobic infections involve multiple offending organisms

Question 5

diaphragm and bacteroides fragilis

Answer 5

bacteroides fragilis is penicillin resistant and is only found in infections below the diaphragm (distinguishes upper from lower GI tract infection)

Question 6

common anaerobes in dental infections

Answer 6

• prevotella
• fusobacterium nucleatum
• peptostreptococcus
• actinomyces

Question 7

common anaerobes in CNS infections

Answer 7

oral anaerobes

Question 8

common anaerobes in otitis media

Answer 8

oral anaerobes

Question 9

common anaerobes in lung infections

Answer 9

• prevotella
• fusobacterium
• peptostreptococcus

Question 10

common anaerobes in peritonitis

Answer 10

• bacteroides fragilis
• fusobacterium
• peptostreptococcus
• clostridium

Question 11

common anaerobes in liver and subphrenic abscesses

Answer 11

colonic flora

Question 12

common anaerobes in OB/GYN infections

Answer 12

colonic flora

Question 13

common anaerobes in perirectal abscesses

Answer 13

colonic flora

Question 14

common anaerobes in skin and muscle infections

Answer 14

clostridium

Question 15

bacteroides fragilis shape and gram stain

Answer 15

gram negative rod

Question 16

which two anaerobes combined cause about 80% of all anaerobic septicemias and about 8% of all septicemias?

Answer 16

bacteroides fragilis and clostridium perfringens

Question 17

where is bacteroides fragilis found

Answer 17

large numbers in large intestine

Question 18

what is the most important characteristic of bactericides fragilis?

Answer 18

penicillin resistant

Question 19

is prevotella sensitive to penicillin?

Answer 19

yes, many strains are

Question 20

which is more sensitive to oxygen when trying to culture? bacteroides fragilis or prevotella?

Answer 20

prevotella

Question 21

shape and gram stain of prevotella

Answer 21

gram negative rod

Question 22

shape and gram stain of fusobacterium

Answer 22

gram negative rod - but very thin and needle shaped

Question 23

is fusobacterium senstive to oxygen? penicillin?

Answer 23

yes to both

Question 24

most common bacteroides infections

Answer 24

intraabdominal, female genital

Question 25

most common prevotella infections

Answer 25

peridontal, sometimes genital

Question 26

most common fusobacterium infections

Answer 26

oral infections, lung abscesses, abdominal

Question 27

name 3 anaerobic gram negative rods

Answer 27

- bacteroides fragilis - prevotella melaninogenicus - fusobacterium

Question 28

what are the spore forming anaerobic gram positive rods?

Answer 28

clostridium species

Question 29

4 non-spore forming anaerobic gram positive rods

Answer 29

- bifidobacterium - corynebacterium - lactobacillus - actinomyces

Question 30

corynebacterium infections

Answer 30

- endocarditis in compromised patients

Question 31

where is corynebacterium usually found?

Answer 31

normal inhabitant of skin

Question 32

where is lactobacillus found?

Answer 32

normally in intestine and vagina

Question 33

lactobacillus is important for:

Answer 33

maintaining low pH

Question 34

actinomyces normally found in

Answer 34

oral pharynx, GI tract

Question 35

what feature is characteristic of actinomyces infections?

Answer 35

sulfur granules, yellow granules seen in lesions that are composed of micro colonies

Question 36

name 2 anaerobic gram positive cocci

Answer 36

- peptostreptococcus | - peptococcus

Question 37

peptostreptococcus normally found in:

Answer 37

mouth, urogenital and GI tract

Question 38

peptococcus normally found in:

Answer 38

mouth, upper resp tract, large intestine

Question 39

name an anaerobic gram negative cocci

Answer 39

veillonella

Question 40

what antibiotics are effective against bacteroides fragilis?

Answer 40

newer cephalosporins such as cefoxitin

Question 41

what is the proper treatment for mixed aerobe-anaerobe infections? (very common)

Answer 41

aminoglycoside + antibiotic for anaerobes like: gentamicin + cefoxitin or gentamicin + clindamycin

Question 42

is penicillin effective against anaerobes?

Answer 42

yes, except for bacteroides fragilis, therefore penicillin alone is not used for infections below the diaphragm