Infectious Disease Compendium

Bacteroides

Microbiology

Anaerobic gram negative rod. B. fragilis, B. distatonis, B. ovatus, B. thetaiotaomicron (these last three put the d-o-t- in DOT), B. gracilus, B. urolyticus, B. vulgatus.

Epidemiologic Risks

A minor anaerobe (30 to 70% have it) but a major pathogen from the colon and really lousy teeth.

Syndromes

Usually part of a mixed infection where abscesses are found anywhere in the body. They require a lack of oxygen and/or dead meat to grow. B. fragilis can cause "marked abdominal pain and nonfebrile inflammatory diarrhea" due to an enterotoxin (PubMed).

Enterotoxigenic Bacteroides may be causal for bowel cancer (too early to be definitive) and Bacteroides in the blood may be associated with an underlying bowel adenocarcinoma (PubMed).

Treatment

Is usually cold steel or a big ole drainage tube. Antibiotics, in my order of preference: metronidazole, carbapenems, penicillin/beta-lactamase inhibitors, clindamycin, cephamycins.

MDR B. fragilis is starting to rear its ugly head (PubMed), resistant to metronidazole, imipenem, piperacillin/tazobactam, clindamycin, cefotetan, ampicillin/sulbactam, and moxifloxacin also was observed..

Notes

Clindamycin resistance is as high as 33%. The DOT group is resistant to cefotetan and cefmetazole. Nothing is as good as metronidazole for strict anaerobes; nothing.