noticeable characteristics of most anaerobic infections:
- abscesses - from native flora
- foul-smelling discharge
- gas in necrotic tissue
where do most anaerobic infections occur?
deep or necrotic tissue where the oxygen is low ( lack of oxidation-reduction potential) and access to endogenous local bacteria is available
predisposing conditions for anaerobic infections:
- pulmonary aspiration
- bowel surgery
- poor dental hygiene
- abortion
- human or animal bites
- trauma
- malignancy
do most anaerobic infections involve only one organism?
- no, in contrast to aerobic infections, most anaerobic infections involve multiple offending organisms
diaphragm and bacteroides fragilis
bacteroides fragilis is penicillin resistant and is only found in infections below the diaphragm (distinguishes upper from lower GI tract infection)
common anaerobes in dental infections
- prevotella
- fusobacterium nucleatum
- peptostreptococcus
- actinomyces
common anaerobes in CNS infections
oral anaerobes
common anaerobes in otitis media
oral anaerobes
common anaerobes in lung infections
- prevotella
- fusobacterium
- peptostreptococcus
common anaerobes in peritonitis
- bacteroides fragilis
- fusobacterium
- peptostreptococcus
- clostridium
common anaerobes in liver and subphrenic abscesses
colonic flora
common anaerobes in OB/GYN infections
colonic flora
common anaerobes in perirectal abscesses
colonic flora
common anaerobes in skin and muscle infections
clostridium
bacteroides fragilis shape and gram stain
gram negative rod
which two anaerobes combined cause about 80% of all anaerobic septicemias and about 8% of all septicemias?
bacteroides fragilis and clostridium perfringens
where is bacteroides fragilis found
large numbers in large intestine
what is the most important characteristic of bactericides fragilis?
penicillin resistant
is prevotella sensitive to penicillin?
yes, many strains are
which is more sensitive to oxygen when trying to culture? bacteroides fragilis or prevotella?
prevotella
shape and gram stain of prevotella
gram negative rod
shape and gram stain of fusobacterium
gram negative rod - but very thin and needle shaped
is fusobacterium senstive to oxygen? penicillin?
yes to both
most common bacteroides infections
intraabdominal, female genital
most common prevotella infections
peridontal, sometimes genital
most common fusobacterium infections
oral infections, lung abscesses, abdominal
name 3 anaerobic gram negative rods
- bacteroides fragilis
- prevotella melaninogenicus
- fusobacterium
what are the spore forming anaerobic gram positive rods?
clostridium species
4 non-spore forming anaerobic gram positive rods
- bifidobacterium
- corynebacterium
- lactobacillus
- actinomyces
corynebacterium infections
- endocarditis in compromised patients
where is corynebacterium usually found?
normal inhabitant of skin
where is lactobacillus found?
normally in intestine and vagina
lactobacillus is important for:
maintaining low pH
actinomyces normally found in
oral pharynx, GI tract
what feature is characteristic of actinomyces infections?
sulfur granules, yellow granules seen in lesions that are composed of micro colonies
name 2 anaerobic gram positive cocci
- peptostreptococcus
- peptococcus
peptostreptococcus normally found in:
mouth, urogenital and GI tract
peptococcus normally found in:
mouth, upper resp tract, large intestine
name an anaerobic gram negative cocci
veillonella
what antibiotics are effective against bacteroides fragilis?
newer cephalosporins such as cefoxitin
what is the proper treatment for mixed aerobe-anaerobe infections? (very common)
aminoglycoside + antibiotic for anaerobes
like: gentamicin + cefoxitin or gentamicin + clindamycin
is penicillin effective against anaerobes?
yes, except for bacteroides fragilis, therefore penicillin alone is not used for infections below the diaphragm