Bacteriocins and other bioactive substances of probiotic lactobacilli as biological weapons against Neisseria gonorrhoeae.

In the search of new antimicrobial agents against Neisseria gonorrhoeae, the bacteriocins-producing probiotic lactobacilli deserve special attention. The inhibitory effects of biosubstances such as organic acids, hydrogen peroxide and each bacteriocin-like inhibitory substance (BLIS) L23 and L60 on the growth of different gonococcal strains were investigated. Different non-treated and treated cell-free supernatants of two probiotic lactobacilli containing these metabolites were used. The aims of this work were (i) to evaluate the antimicrobial activity of the biosubstances produced by two probiotic lactobacilli, estimating the proportion in which each of them is responsible for the inhibitory effect, (ii) to define their minimum inhibitory concentrations (MICs) and, (iii) to determine the potential interactions between these biosubstances against N. gonorrhoeae. The main antimicrobial metabolites were the BLIS-es L23 and L60 in comparison with other biosubstances. Proportionally, their contributions to the inhibition on the gonococcal growth were 87.28% and 80.66%, respectively. The MIC values of bacteriocins were promising since these substances, when diluted, showed considerable inhibitory activity for all gonococci. In the interaction between bacteriocins, 100% of synergism was found on the gonococcal growth. In summary, this study indicates that both L23 and L60 could potentially serve to design new bioproducts against N. gonorrhoeae.

Synergistic effect between two bacteriocin-like inhibitory substances produced by Lactobacilli Strains with inhibitory activity for Streptococcus agalactiae.

Group B streptococci (GBS) are bacterial species that colonize the vagina in pregnant women and as such may cause serious infections in neonates that passed through the birth channel. The objective of this work was to study the inhibitory activities produced by each bacteriocin-like inhibitory substance (BLIS) of Lactobacillus rhamnosus L60 and Lactobacillus fermentum L23, and the effects of the combined BLIS-es of these lactobacilli on GBS. The interactions between the BLIS-es were assessed by qualitative and quantitative methods on agar plates. The minimum inhibitory concentrations (MICs) and fractional inhibitory concentrations (FICs) were determined by a modification of the broth microdilution and checkerboard methods, respectively. Antibiotic susceptibilities of all S. agalactiae strains were assayed and the results of these tests were evaluated for statistical significance. A 7.5% of GBS isolates were recovered from 760 pregnant women and 91% of those strains were susceptible to each BLIS produced by L. fermentum, L. rhamnosus, and also to a mixture of them. The comparisons among the BLIS-es showed statistically significant differences, with a combination of the BLIS-es from the two Lactobacillus species being better than the BLIS of each one alone (P < 0.05) as GBS growth inhibitors. Synergistic activities between the BLIS-es were found on 100% of susceptible GBS strains, MICs ranges of BLIS of L23 and L60 were 80-160 and 160-320 UA ml(-1), respectively. By the checkerboard method, the BLIS-es combination showed synergistic effect on all sensitive strains tested, with values of FICs ranging from 0.131 to 0.218. The BLIS-es produced by these lactobacilli of vaginal origin were able to inhibit S. agalactiae isolates. The results indicate that these strains may have probiotic potential for the control of GBS in women and may consequently prevent GBS infections in newborns.

Antimicrobial activity, inhibition of urogenital pathogens, and synergistic interactions between lactobacillus strains.

Lactobacillus fermentum strain L23 and L. rhamnosus strain L60 were selected as an alternative treatment to prevent or treat urogenital infections based on their probiotic properties and production of bacteriocins. The objectives of the present work were to study the inhibitory activities of these two bacteriocin-producing strains, and to analyze the interactions between pairs of bacteriocins that inhibit urogenital pathogens. Antimicrobial activity tests of L23 and L60 were performed by a diffusion method with 207 bacterial strains, isolated from female patients presenting a urogenital infection. Inhibitory substances interaction tests were carried out by using a streak-diffusion method on agar plates. One hundred percent of the clinical isolates showed sensitivity to the antimicrobial substances produced by L23 and L60. The selected lactobacilli produced larger inhibition halos when compared to several antibiotics commonly used for treating these infections. Synergistic interactions and indifferent interactions were recorded in 68.6% and 31.4% of the cases, respectively. No antagonistic interactions were observed. In conclusion, the bacteriocin-producing strains L23 and L60 are potential candidates for probiotic prophylaxis and treatment of urogenital disorders in women.