Anti-Candida activity of beneficial vaginal lactobacilli in in vitro assays and in a murine experimental model

Abstract

Vulvovaginal candidiasis (VVC) is one of the most frequent infections affecting women worldwide. Healthy vaginalmicrobiota is dominated by lactobacilli, which form a strong defense line against pathogens. In this work, in vitroantimicrobial properties of thirty vaginal Lactobacillus strains were evaluated against eleven Candida vaginal clinical isolates,employing three different methods. Also, the effect of intravaginal (i.va.) administrations (preventive, therapeutic andpreventive-therapeutic) of L. reuteri CRL1324 or L. rhamnosus CRL1332 strains against the i.va. challenge with Candida albicansC2 (C.a.) was evaluated in a murine experimental model. From the results of agar overlay and liquid medium assays theselected lactobacilli strains have shown to inhibit the growth of at least one Candida strain. The inhibition was mainly dueto the effect of organic acids. Anti-Candida activity was not evidenced in the agar plate diffusion method. In theexperimental murine model, only preventive-therapeutic administration of both lactobacilli was able to significantly reduceviable C.a. numbers recovered in vaginal washes and the leukocyte influx induced by the fungi. In conclusion, lactobacilliexhibited in vitro and in vivo antimicrobial effects on Candida, suggesting that they could be promising candidates forprotection against VVC. Lactobacilli predominant in human vagina and protect from VVC. The manuscript reports different methods to determine lactobacilli inhibitory effect at the laboratory, and protection against Candida in murine vagina.