Isolation and Characterization of Inhibitor(s) Produced by Vaginal Streptococcus spp. with Bacteriocin-Like Inhibitory Activity against Vaginal Lactobacillus spp., Which May Be Associated With Bacterial Vaginosis Development in the Vagina
Kelly, Maureen C.
Development of the vaginal syndrome bacterial vaginosis is characterized by an alteration in vaginal microflora, which includes the decline in the Lactobacillus population that are generally dominant in the vagina. Mechanisms which could account for the disappearance of lactobacilli are not well understood. As Streptococcus spp. at other sites within the body are able to produce bacteriocin-like inhibitory substances, the aim of this study was to test vaginal Streptococcus spp. for the production of inhibitors antagonistic to the growth of vaginal Lactobacillus spp. Seventy-two vaginal Streptococcus spp. isolates were tested for inhibitor production with 32 strains of vaginal lactobacilli as indicator strains using the deferred antagonism technique on blood agar. Two streptococcal strains, 46-2 and 62-6, exhibited strong, reproducible inhibitory activity. Results from initial characterization experiments suggested the inhibitor(s) produced by strain 46-2 either required blood for production or that the inhibitory activity was due to blood break-down products. By contrast, the inhibitor(s) of strain 62-6 were produced in the absence of blood both in the growth and on the detection media. The inhibitor(s) produced by strain 62-6 was subjected to physico-chemical characterization assays and shown to be heat-stable (up to 100°C for 30 minutes), stable for up to 14 days when stored at 4°C, sensitive to pepsin, but not trypsin or a-chymotrypsin or proteinase K or catalase, retained on a membrane filter of 0.22µm pore size, and produced under microaerophilic (5% C02) and anaerobic conditions. In addition, the observed inhibition was not due to the presence of either hydrogen peroxide or the pH of the growth media. These results are consistent with the production of a bacteriocin-like inhibitor by strain 62-6.
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