Estudo da microbiota vaginal de mulheres com e sem vaginose bacteriana, com ênfase em Gardnerella vaginalis e Lactobacillus spp.

Abstract

Bacterial vaginosis (BV) is a condition associated with alterations in the vaginal microbiota, which is normally dominated by Lactobacillus spp. and becomes mainly replaced by Gardnerella vaginalis. Understanding vaginal microbial ecology is essential for improving therapeutic strategies, since conventional treatments may disrupt the autochthonous microbiota, promote reinfections, select resistant microorganisms, and cause adverse effects. In this context, the use of probiotic microorganisms emerges as a promising therapeutic alternative, as these agents can colonize the vaginal tract, inhibit urogenital pathogens, present a low risk of resistance selection, and contribute to the restoration of the vaginal microbiota. This study aimed to characterize the vaginal microbiota of healthy women and women with BV, with emphasis on Gardnerella vaginalis and Lactobacillus spp.; to determine the antimicrobial susceptibility profile of G. vaginalis strains; and to select Lactobacillus strains with probiotic potential evaluated in vitro and in vivo, using gnotobiotic animals. Seventy women participated in the study, 30 with BV and 40 without BV, assisted at the Gynecology Service of the Hospital das Clínicas, Federal University of Minas Gerais (UFMG). Vaginal specimens were cultured on selective media, and bacterial species were identified using previously standardized methodologies. G. vaginalis strains were subjected to susceptibility testing against the antimicrobials most commonly used in clinical practice. Lactobacillus spp. strains were evaluated for probiotic potential through the production of antagonistic substances using the overlay technique and by hydrogen peroxide production in vitro. The selected strain, Lactobacillus johnsonii, isolated from a healthy patient, was inoculated into gnotobiotic mice, which were subsequently challenged with G. vaginalis, with or without hormonal induction. The results demonstrated a higher frequency of G. vaginalis in women with BV, whereas Lactobacillus spp. predominated in healthy women, especially L. crispatus, L. jensenii, and L. johnsonii. Lactobacillus strains isolated from women without BV showed significantly higher production of antagonistic substances and hydrogen peroxide. The selected L. johnsonii strain was able to colonize gnotobiotic animals and provided partial protection against experimental infection with G. vaginalis, as evidenced by bacterial counts and histopathological analyses. Hormonal administration did not significantly influence colonization by G. vaginalis but affected colonization by L. johnsonii. It is concluded that certain Lactobacillus spp. species are essential for maintaining the health of the vaginal ecosystem, whereas G. vaginalis plays a central role in the etiology of BV. In addition, a Lactobacillus johnsonii strain with promising probiotic characteristics was identified, as demonstrated in vitro and in vivo.