Inhibition of Vaginal Lactobacilli by a Bacteriocin-Like InhibitorProduced byEnterococcus faecium62-6: Potential Significancefor Bacterial Vaginosis

[摘要] Objective:Bacterial vaginosis (BV) is characterized by a shift in vaginal tract ecology, which includes a decreasein the concentration and/or prevalence of facultative lactobacilli. Currently, mechanisms which could accountfor the disappearance of lactobacilli are not well understood. The objective of this study was to determine whethervaginal streptococci/enterococci can produce bacteriocin-like inhibitors antagonistic to vaginal lactobacilli.Methods:Seventy strains of vaginal streptococci or enterococci were tested for antagonistic activities againstvaginal lactobacilli using the deferred antagonism technique.Results:One strain,Enterococcus faecium62-6, which strongly inhibited growth of lactobacilli was selected forfurther characterization. The spectrum of inhibitory activity of strain 62-6 included Gram-positive organismsfrom 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℃, lessthan 114 days) and pH- (4–7) stable. The sensitivity of inhibitor-containing supernatants to pepsin andα-chymotrypsin suggested an essential proteinaceous component. The inhibitor was sensitive to lipase but resistantto lysozyme. Dialysis of inhibitor-containing culture supernatants suggested a molecular mass greater than12 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 of107cfu/ml, suggesting that production may be regulated by quorum sensing.Conclusions:These results may have clinical significance as a novel mechanism to account for the decline of vaginalLactobacilluspopulations and contribute to both the establishment and recurrence of BV.

[学科分类] 妇产科学