The role of microbiota in the etiology of dysplastic and oncological diseases of the cervix, vagina, and vulva: A review

The vaginal microbiota of a healthy woman is a unique microecosystem comprising more than 300 bacterial species. The main vaginal bacteria of a healthy woman are Lactobacillus spp. (90–95%), with the most common being L. crispatus, L. iners, L. jensenii, and L. gasseri. Based on the dominant Lactobacillus species, five types of communities are distinguished: CST I, II, III, IV, and V. Lactobacilli ensure a normal vaginal pH (3.8–4.4) and inhibit the growth of other microorganisms, particularly Escherichia coli, Trichomonas vaginalis, Gardnerella vaginalis, Prevotella bivia, etc. Different lactobacilli species produce different levels of reactive oxygen species. Many studies demonstrated a close relationship between vaginal microbiota disturbance and the development of malignancies, particularly cervical, vagina, and vulvar cancer. This review analyzes published studies, which showed a positive correlation between a low content of lactobacilli, an increase in the abundance of pathogenic bacteria, and cancer of the anogenital region; the association between some bacteria, the persistence of the human papillomavirus, and the development of dysplasia of the lower reproductive system was demonstrated. Timely diagnosis and treatment of vulvovaginal infections and vaginal dysbiosis would reduce the risk of human papillomavirus persistence and, consequently, the development of dysplasia and cancers of the lower genital tract.