Fibronectin binding of Lactobacillus species isolated from women with and without bacterial vaginosis.

Lactobacilli isolated from the vaginas of healthy women (39 strains) and from the vaginal discharge of women with bacterial vaginosis (15 strains) were investigated for their binding to 125I-fibronectin. Nine of the 54 strains bound fibronectin at pH 7.2. The binding capacity of these nine strains was about the same as that observed with Staphylococcus aureas Cowan 1. The binding was specific; an excess of unlabelled fibronectin or its amino-terminal 29-kDa fragment effectively competed for binding, whereas bovine serum albumin, human IgG and orosomucoid did not. Incubation of lactobacilli with fibronectin for different periods revealed a time-dependent increase in binding. Lowering the pH to 4.0 increased the binding capacity of all of the lactobacilli tested; binding occurred with strains that had previously failed to bind at pH 7.2. The increased binding of lactobacilli to fibronectin at a low pH may play a role in the maintenance of the ecological balance of the vagina.