Anaerobic gram negative rod.
Most common anaerobic infection "below the diaphragm."
Colonizes GI tract of humans, colon>small bowel.
Other Bacteroides spp. such as B. thetaiotaomicron and B. ovatus are less frequently isolated, but may occur in similar infections.
Metronidazole and piperacillin-tazobactam remain drug of choice for non-B. frag Bacteroides spp.