A study of the candidate virulence factors of Bacteroides fragilis

Abstract

Bactevuides fragifis strains were classified as virulent or avirulent on the basis of their clearance from the subcutaneous tissues of mice. To determine the factors which may contribute to the virulence of B.fragifis strains, we studied encapsulation, hydrophobicity, growth rate, serum sensitivity, agglutination with erythrocytes of different origin, and neuraminidase production. The strains of the virulent group displayed a higher growth rate in broth and a lower sensitivity to the bactericidal activity of serum than the strains of the avirulent group. They also agglutinated different types of erythrocytes more strongly than did the avirulent strains. No significant differences were found between the two groups of strains as regards encapsulation, hydrophobicity and neuraminidase activity.

Virulence markers and antimicrobial susceptibility of bacteria of the Bacteroides fragilis group isolated from stool of children with diarrhea in São Paulo, Brazil

“…The capsular polysaccharide B. fragilis acts as a protector against neutrophil phagocytes and the complement bactericidal activity; it can produce abscesses in animals (Lindberg & Weintraub 1985). Moreover, all the tested strains showed characteristics such as β-hemolytic, hydrophilic, and human or horse serum resistant, in accordance with Rotimi and Eke (1984), Oyston and Handley (1990), and Namavar et al (1991).…”

“…Thus, the resistance of the B. fragilis strain against human or horse sera may explain its pathogenic potential in severe clinical infections (Rotimi & Eke 1984). Namavar et al (1991) showed that avirulent B. fagilis strains were more sensitive to serum than the virulent ones, indicating that the complement is crucial for killing of avirulent strains.…”

“…Capsule detection -Capsules were detected by using a Hiss stain with modifications (Namavar et al 1991). Each isolate was anaerobically grown in peptone-yeast extract (PY) with 1% glucose.…”

“…Serum resistance -Serum resistance was tested using human and horse sera (Namavar et al 1991). Each serum was pooled, and aliquots of 1 ml were stored at -20°C.…”

Avaliação quantitativa de enteropatógenos em crianças com e sem diarréia na cidade de São Paulo, SP.

“…Bacteroides fragilis possui também um elevado potencial invasivo, processo que é favorecido pela produção de proteinases, neuraminidase, hialuronidases, fosfatases e DNAses (JOTWANI et al, 1991;NAKANO et al, 2007;NAMAVAR et al, 1991). …”