In vitro interactions between lactobacilli and other microorganisms occurring in the vaginal flora.

The present study shows that certain species of lactobacilli isolated from the human vagina can, on artificial culture media, inhibit growth of other bacterial species recovered from the same site. The antibiosis seems to be mediated by one or more extracellular compounds produced by the lactobacilli acting, over a wide pH-range, on both Gram-positive and Gram-negative aerobic and facultatively anaerobic bacteria as well as yeast fungi. Likewise, certain bacteria suppressed growth of lactobacilli under similar test conditions. In some instances a stimulatory effect of the growth of the lactobacilli was noted. The antibacterial and antifungal principles demonstrated in the present study can not be classified, to the best of our knowledge, as any previously known antibiotic principle of lactobacilli.