Pelvic inflammatory diseases occupy a special place in the structure of general morbidity, and are polymicrobial in nature with dominance of opportunistic microorganisms, in particular bacteria of the family Enterobacteriaceae. The aim was to study the composition of the vaginal microbiota in women of reproductive age with pelvic inflammatory diseases, as well as to determine the sensitivity of isolated microorganisms to antibiotics and bacteriophages. The study included 70 women of reproductive age, among them 37 were diagnosed with colpitis and cervicitis, 33 women in the comparison group (women screened for a diagnosis). Isolated microorganisms were identified by abdominoperineal methods, including the disk diffusion method to determine the sensitivity of microorganism cultures of Enterobacteriaceae family to antibiotics, and the method of crosses (evaluation of lytic activity of bacteriophages by the number of crosses) to determine the sensitivity to specific therapeutic bacteriophages. Vaginal biocenosis was characterized by deficit of lactobacilli (< 106 CFU/ml in 100 %), the presence of conditionally pathogenic microflora: bacteria of Enterobacteriaceae family, coccal flora and Candida fungi. From 60.0 to 89.3 % of Enterobacteria strains were resistant to aminoglycosides and quinolones, but also had a low level of sensitivity to therapeutic bacteriophages. The obtained data indicate the reduction of colonization resistance of vaginal mucosa in pelvic inflammatory diseases and specify the need to use medicinal drugs only under medical supervision to prevent clinically significant drug resistance.