Abstract
Objective: Bacterial vaginosis (BV) is characterized by a shift in vaginal tract ecology, which includes a decrease
in the concentration and/or prevalence of facultative lactobacilli. Currently, mechanisms which could account
for the disappearance of lactobacilli are not well understood. The objective of this study was to determine whether
vaginal streptococci/enterococci can produce bacteriocin-like inhibitors antagonistic to vaginal lactobacilli.Methods: Seventy strains of vaginal streptococci or enterococci were tested for antagonistic activities against
vaginal lactobacilli using the deferred antagonism technique.Results: One strain, Enterococcus faecium 62-6, which strongly inhibited growth of lactobacilli was selected for
further characterization. The spectrum of inhibitory activity of strain 62-6 included Gram-positive organisms
from the vaginal environment, although native lactobacilli from the same host were resistant to inhibitor action.
Following growth inMRSbroth the strain 62-6 inhibitor was shown to be heat- (100℃, 30 minutes), cold- (4℃, less
than 114 days) and pH- (4–7) stable. The sensitivity of inhibitor-containing supernatants to pepsin and
α-chymotrypsin suggested an essential proteinaceous component. The inhibitor was sensitive to lipase but resistant
to lysozyme. Dialysis of inhibitor-containing culture supernatants suggested a molecular mass greater than
12 000 Da. All physicochemical properties were consistent with its classification as a bacteriocin-like inhibitor.
Kinetic assays demonstrated a sharp onset of inhibitor production coinciding with a concentration of 62-6 of