Evaluation of antipathogenic activity and adherence properties of human Lactobacillus strains for vaginal formulations

Aims: To test different Lactobacillus strains for their antipathogenic activity towards Candida strains and their adhesion properties for the preparation of vaginal ovules and douches to be used in vaginal candidiasis prevention. Methods and Results: Five strains of lactobacilli were tested for their antimicrobial potential against different clinically isolated Candida strains. They were also screened for their ability to produce hydrogen peroxide and to coaggregate with pathogens. Adhesion properties of the five different Lactobacillus strains to HeLa cells and the presence of arcA gene were also assessed. The in vitro experiments demonstrated that all the five Lactobacillus strains tested possessed inhibitory action against the Candida strains using the radial streak method, but the effect is strain dependent. The same situation arises with regard to the ability of coaggregation that is present in all the strains into different degrees. Only Lactobacillus rhamnosus IMC 501® and Lactobacillus paracasei IMC 502® were able to produce H2O2 and none of the strains possess arcA gene. The most adherent strains to HeLa cells were Lact. rhamnosus IMC 501®, Lact. paracasei IMC 502® and also their combination SYNBIO®. This latter was selected for the preparation of ovules and douches using different matrix. Witepsol® ovules have proved the best formulation in terms of probiotic viability. Conclusions: Lactobacillus rhamnosus IMC 501®, Lact. paracasei IMC 502® and SYNBIO® were able to produce H2O2, to coaggregate and to exert antimicrobial activity against pathogenic Candida strains and to strongly adhere to HeLa cells. All these properties together with those technological make these strains good candidates for the realization of formulations suitable for vaginal health. Significance and Impact of the Study: To develop new vaginal formulations taking into account the impact of probiotic strains on pathogens as well as the technological properties of the strains to validate their effectiveness in human health.