Fibronectin binding and cell surface hydrophobicity contribute to adherence properties of group B streptococci.

The matrix protein, fibronectin, which is detectable in various tissues, when present in the vaginal fluid of women in labour, indicates the rupture of membranes. It is known that many bacteria adhere to fibronectin, thus establishing a first step of infection. In women in labour, group B streptococci are common agents of chorioamnionitis. For group B streptococci, unspecific adherence mechanisms like negative net charge and hydrophobic interactions have already been discussed in literature. In the present study, group B streptococci isolates from 57 patients with premature rupture of membranes were studied for fibronectin binding activities, using a particle agglutination assay and for cell surface hydrophobicity, by testing adhesion to hydrocarbons. Particle agglutination assays and adhesion assays were done with strains grown on blood-containing media and media without blood. Fibronectin binding was shown to be present in 14 and 11 out of 57 isolates grown on Mueller-Hinton and Tryptic Soy agar, respectively. When the strains were grown on blood-containing media, fibronectin-binding was found to be concomitant with decreased hydrophobicity. According to the results obtained in a total of 57 strains, cell surface hydrophobicity is an unspecific adhesion factor in group B streptococci. Fibronectin binding seems to be an additional adherence factor in some of the strains and may be assumed to play a major role in establishing infectious processes.