Bacteroides

Bacteria of this genus are a significant part of the intestinal flora, some species are potentially pathogenic. Their membrane contains sphingolipids, and there is diaminopimelic acid in their wall.

Bacteroides are gram-negative pleomorphic rods with round ends, usually encapsulated. They are typical for being resistant to bile acids. They massively colonize both the large and small intestine, where they play a role in digesting complex molecules, and the upper respiratory tract. In the vagina the species B. fragilis, B. capillosus, or B. ureolyticus are commensal species. Their endotoxin has low biological activity.

Pathogenicity
B. fragilis is among the most significant pathogens, with a polysaccharide capsule as its virulence factor. It can cause peritonitis, infections during surgery in the gastro-intestinal tract, and appendicitis. It inhibits phagocytosis and like other species of this genus it’s resistant to beta-lactames, aminoglycosides, and recently there have appeared strains resistant to erythromycin and tetracycline. Another notable species in the Bacteroides genus are B. ovatus, B. vulgatus, and B. gracilis.

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