Characterization of Vaginal Lactobacillus Strains and Their Potential Antagonistic Effects on Candida albicans

Aims: To characterize Lactobacillus strains for potential beneficial effects, especially for inhibition of Candida albicans growth.
Materials and Methods: Twelve vaginal Lactobacillus strains belonging to five species from our laboratory collection were studied. The acid production and hydrogen peroxide (H2O2) production were determined. The biofilm formation ability was measured by a semi-quantitative microtiter plate assay. Besides the detection of autoaggregation and coaggregation capacities with C. albicans using a spectrophotometric assay, aggregating clusters were observed by light microscopy. The spot inhibition, agar overlay and Oxford Cup methods were used to test antagonistic activities of Lactobacillus strains against C. albicans.
Results: Seven strains of L. fermentum (A011, A024, A025, A035, A041, A044 and A081) and L. salivarius A023 were revealed to decrease the medium pH below 4.5 just within six hours due to the rapid growth. L. jensenii A083 and L. gasseri A054 were the best biofilm formers in polystyrene plates, whereas the other ten strains could form biofilm with varying affinities. In addition to significant H2O2 production found in L. jensenii A083, L. crispatus A014 and A055, these strains showed strong autoaggregation and coaggregation abilities with C. albicans (ATCC 90029 and Z03). L. salivarius A023, L. fermentum A025 and L. crispatus A014 displayed strong activities against C. albicans in spot inhibition and agar overlay assays.
Conclusion: The potential beneficial properties of Lactobacillus spp. were strain specific. Among the tested strains, L. salivarius A023, L. fermentum A025 and L. crispatus A014 might be better candidates for further investigation on the inhibition of C. albicans growth.