Growth and biofilm formation of vaginal lactobacilli in simulating physiological urogenital conditions

MARIA CECILIA LECCESE TERRAF; MARIA SILVINA JUAREZ TOMAS; ELENA BRU; CLARA SILVA; MARIA ELENA FÁTIMA NADER

Tucuman

Simposio; IV Simposio Internacional de Bacterias Lacticas (SIBAL); 2013

CERELA-CONICET

Lactobacillus species are the dominant microorganisms in the vaginal environment, and inhibit pathogenic microorganisms by different mechanisms, as production of organic acids, hydrogen peroxide and bacteriocins. Different syndromes, as bacterial vaginosis, aerobic vaginitis and urinary infection affect the balance and disrupt the vaginal ecosystem. The intravaginal administration of pharmaceutical formulas containing beneficial strains has been proposed to restore the healthy vaginal microbiome. The adhesion and biofilm formation (communities of bacteria, included in a self-synthesized extracellular polymeric matrix) are strain-properties that promote and help their permanence in the human vagina. The objective of this study was to evaluate if beneficial vaginal lactobacilli (BVL) strains are able to grow and to form biofilm in laboratory experimental models in sterilized urines pools and in a culture medium simulating the vaginal content. Lactobacillus rhamnosus CRL1332, Lactobacillus reuteri CRL1324 and Lactobacillus gasseri CRL1263 were evaluated. L. rhamnosus CRL1332 and L.reuteri CRL1324 are biofilm-forming strains in MRS broth without Tween 80 (MRS-T) and inhibits the growth of urogenital pathogens. L.gasseri CRL1263, a non-biofilm forming strain in MRS-T, was used as control. A 3x2x2 factorial design was applied, evaluating three BVL strains, two media (pooled human urine (PU) and medium simulating vaginal fluid (MSVF) and two Tween 80 concentrations (0 and 0.1%). Growth kinetic was determined by optical density (OD) at 540 nm, number of viable cells and pH. Organic acids (acetic and lactic) levels were quantified by HPLC. Biofilm formation under different conditions was carried out by crystal violet-staining microplate assay. Results were analyzed by ANOVA (general linear mixed models). The BVL strains showed different behavior under the various conditions assayed. L. rhamnosus CRL1332 and L. reuteri CRL1324 were able to grow in MSVF and PU with and without Tween (PU-T). L. gasseri CRL 1263 has grown in MSVF with Tween, but not without Tween (MSVF-T). However, the growth of this strain in PU and in PU-T was similar. The growth of L. gasseri was significantly higher in MSVF than in PU. When estimating the relationships between OD and pH, significant negative correlations through time were observed for the three strains. Among the three factors assayed, only the concentration of Tween 80 exerted statistically significant effects on biofilm formation. L. rhamnosus CRL1332 and L. reuteri CRL1324 were able to form biofilm in MSVF-T and PU-T. L. gasseri CRL 1263 formed biofilm only in MSVF-T.The results demonstrate that BVL can grow, maintain their viability and form biofilm in conditions simulating the physiological environment of the tracts in which they will be applied. These beneficial and functional characteristics are basic selection criteria for inclusion of BVL in products to be used in the urogenit