Bacteroides fragilis

1. a species name given to a group of closely related bile-resistant, saccharolytic organisms comprising all the former subspecies of B. fragilis (fragilis, distasonis, ovatus, thetaiotaomicron, vulgatus), which are now considered to be separate species, along with a few other species, such as B. uniformis. Collectively, the organisms constitute the numerically dominant species found in the human intestine and are the most commonly encountered anaerobic bacteria in clinical specimens. They are also present normally in the mouth, throat, and vaginal tract. 2. one of the species included in the B. fragilis group of bacteria. It is the most important of the anaerobic bacteria causing human infection, being most frequently implicated in intra-abdominal infections, but is also found in bacteremias, abscesses, and other lesions throughout the body. Organisms in this species are more resistant to antibiotics than any other anaerobe.