The genus bacteroides

Abstract

Bacteroides species has a large genome that allows it to adapt to particular environments or conditions. The genome of Bacteroides fragilis, the type species of the genera, is also quite plastic and contains a large number of moving elements such as plasmids, transposons, and conjugative transposons that are important in dissemination of resistance and virulence elements. Thus, BF may serve as a gut reservoir for resistance determinants that they can pass on to much more virulent bacteria that move through the gut only periodically. Bacteroides fragilis is normally a human gut commensal or even a symbiont. BF can become a virulent pathogen if it escapes its gastrointestinal niche as a consequence of disruption of the integrity of the intestinal barrier due to surgery, trauma, or disease. BF only accounts for 2 % of the total gut Bacteroides, but it is the agent of >70 % of Bacteroides infections. BF can be found in almost every type of infection including bacteremia, serious gynecological infections, peritonitis, soft tissue infections, and brain abscess. Some BF contain a gene coding for an enterotoxin (ETBF) that can cause severe diarrheal disease. BF makes a polysaccharide capsule (PSA) that is important in the immune development of the newborn and may be important in preventing colitis; ironically, PSA is required for B. fragilis to initiate abscess formation in experimental models.