Urogenital pathogen inhibition and compatibility between vaginal Lactobacillus strains to be considered as probiotic candidates

Abstract

ObjectivesTo evaluate the production of inhibitory substances against several urogenital pathogens and to determine the compatibility between selected vaginal lactobacilli to be considered as probiotic candidates. Study designThe inhibitory activity of 38 vaginal Lactobacillus strains against urogenital pathogens was assessed using the agar plate diffusion. MethodThe production of hydrogen peroxide was determined by the semi-qualitative tetramethyl-benzidine-peroxidase assay and that of lactic acid by high performance liquid chromatography. Pre-selected lactobacilli were genetically identified by ribosomal 16S-DNA sequencing and used to determine the compatibility of strains. Correlation values between some inhibitory properties were calculated. Results45% of the lactobacilli assayed inhibited the growth of various urogenital pathogens, except Candida albicans, mainly by the effect of organic acids. Even though 71% of the Lactobacillus strains produced hydrogen peroxide in the semi-qualitative test, the antimicrobial effect of the oxidative metabolite on pathogens was not detected under the experimental conditions assayed. On the other hand, the inhibition spectrum of salivaricin CRL 1328 was widened with respect to the one previously reported by our research team. With respect to the degree of interaction between the pre-selected lactobacilli, most of them showed inhibition of at least one strain, mainly due to the effects of both organic acids and hydrogen peroxide. ConclusionSeveral lactobacilli that showed inhibitory activity against urogenital pathogens or produced hydrogen peroxide are compatible between them. Therefore, different potential combinations of strains are proposed for their inclusion in the design of probiotic products to be vaginally administered for the prevention of urogenital infections in women.