Incubation of normal human erythrocytes with the supernatant of centrifuged culture of some strains of Bacteroides fragilis results in the exposure of Tk polyagglutination determinants on the erythrocyte membrane. These determinants are present on non papain-labile structures and are probably exposed by an enzyme mechanism. Other strains of B. fragilis were found to produce neuraminidase, haemo...

In order to determine the therapeutic value of penicillins in the management of anaerobic infections caused by Bacteroides fragilis, the antibacterial activity of penicillin G, ampicillin, and carbenicillin against 10 strains of B. fragilis subsp. fragilis, isolated from clinical material, was studied. This was undertaken by using a triple-layer technique, enzymatic inactivation of the antibiot...

Radioimmunoassay methods were evaluated for immunoglobulin G and immunoglobulin M antibodies against Bacteroides fragilis antigen. Of 12 serum samples from patients with B fragilis infections, 9 had higher concentrations of immunoglobulin G antibodies than any from 11 control subjects. Of 9 serum samples from infected patients, 6 had higher concentrations of immunoglobulin M than any from contr...

Bacteroides fragilis is a bacterium that resides in the normal human gastro-intestinal tract; however, it is also the most commonly isolated Gram-negative obligate anaerobe from human clinical infections, such as intra-abdominal abscesses, and the most common cause of anaerobic bacteraemia. Abscess formation is important in bacterial containment, limiting dissemination of infection and bacterae...

A medium, Bacteroides fragilis bile-esculin (BBE) agar, was designed for the selection and, presumptive identification of the B. fragilis group. BBE agar contains bile, esculin, ferric ammonium citrate, hemin, and gentamicin in a Trypticase soy agar base. Growth in the presence of 20% bile and esculin hydrolysis, detected by blackening of the medium, provide presumptive evidence for the identif...

Clinical isolates of the Bacteroides fragilis group (n = 387) were collected from patients attending nine Canadian hospitals in 2010-2011 and tested for susceptibility to 10 antimicrobial agents using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method. B. fragilis (59.9%), Bacteroides ovatus (16.3%), and Bacteroides thetaiotaomicron (12.7%) accounted for ~90% of i...

Bacteroides fragilis colonizes dog guts both as a commensal and as an opportunistic pathogen. This study aims to evaluate virulence factors of 13 B. fragilis strains isolated from dog intestinal tracts and their ability for biofilm formation. Capsules were detected in all the evaluated strains. A total of 61.5% of all strains were biofilm producers. These attributes most likely play an importan...

Orientations of the seven invertible polysaccharide biosynthesis locus promoters of Bacteroides fragilis were determined from bacteria grown in vitro, from feces of monoassociated and complex colonized mice, and from B. fragilis-induced murine abscesses. Bacteria grown in vivo have greater variability in orientation of polysaccharide locus promoters than culture-grown organisms.

The potential for mutual enhancement of growth of the Bacteroides fragilis and B. melaninogenicus groups and the aerobic and facultative organisms commonly isolated with them in mixed infections was evaluated. Enhancement was studied by measuring the relative increase in CFU of the two bacterial components inducing subcutaneous abscesses in mice. Of the 42 combinations between three isolates ea...

Strains (115) of Bacteroides fragilis were identified at the subspecific level and were tested for susceptibility to ampicillin, cephalothin, chloramphenicol, clindamycin, penicillin, and tetracycline using an agar dilution technique. We tested the following strains: B. fragilis subsp. distasonis, 12; B. fragilis subsp. fragilis, 39; B. fragilis subsp. ovatus, 10; B. fragilis subsp. thetaiotaom...