Effect of Bacteriocin-like Inhibitory Substances Produced by Vaginal Lactobacilli on Group B Streptococcus

Abstract

Reduction of vaginal Lactobacillus population leads to overgrowth of opportunistic organisms such as Streptococcus agalactiae (Group B Streptococcus, GBS), which causes life threatening neonatal infections. The activities of bacteriocin-like inhibitory substances (BLIS) produced by Lactobacillus species isolated from the vagina of pregnant women were tested on GBS. Crude Bacteriocins were produced from seven Lactobacillus isolates using de Man Rogosa Sharpes media. Partial purification was done using ammonium sulphate saturation (90%) and dialysis methods. The antibacterial effects of the crude and partially purified BLIS were carried out by disc Agar diffusion method. The BLIS from strains R5 and L2 gave the highest and lowest inhibition zone diameter (IZD) of 16.9 mm and 12.1 mm, respectively, for the crude extracts and 18.5 mm and 14.2 mm, respectively, for the partially purified extracts. All the BLIS had their strongest activity at 30°C and decreased with increase in temperature. BLIS from strains L3 and L4 lost their activities at 100°C. The activities of all the BLIS were higher at acidic pH. The IZD of the combined crude extract was 19.06 mm, while that of the combined partially purified extracts was 21.07 mm. The combined BLIS had higher activity than each of the single compound. There were no statistical difference between the sensitivities of the partially purified BLIS and the crude BLIS (P > 0.05). The findings of this study show that BLIS produced by vaginal Lactobacilli spp. can be used as probiotics for the control of GBS and that combining the BLIS may be more effective.

Keywords: Antibacterial, Group B Streptococci, Vaginal Lactobacillus