has been isolated from several human and non-human monomicrobial and mixed infections. In this study, some virulence markers and the antimicrobial susceptibility of bacteria of the B. fragilis
group isolated from children's stools were evaluated. All the 64 isolates showed the following characteristics: capsulated, b-hemolytic, hydrophilic, and serum-resistant. Only, 24 (37.5%) strains were resistant at 60°C, for 30 min, and among them, 12 (18.75%) were resistant at 60°C, for 60 min. Also, none strain was resistant at 100°C. Four strains were able to hemagglutinate erythrocytes and D-mannose, D-galactose, D-arabinose, and D-xylose inhibited hemagglutination in 2 B. fragilis
strains (p76a, p76b). The hemagglutination in the strain B. uniformis p3-2 was inhibited by D-xylose and D-galactose. The bft gene detection and the enterotoxin production were observed only in 13 EF-enterotoxigenic species. Fragilysin activity was confirmed on HT-29 cells. The antimicrobial determination confirmed that both imipenem and metronidazole were efficient against B. fragilis
species; all the strains were resistant to lead and nickel. Plasmids of 2.9, 4.4, 4.8, and 8.9 kb were observed in 6 tested strains. These results show the values of the species identification from clinical infections, as well as of the periodic evaluation of the resistance patterns of the B. fragilis
group at Brazilian medical institutions.