Hormonal modulation of the vaginal bacterial flora in experimental polycystic ovarian disease

Rats exposed to constant light develop polycystic ovarian (PCO) disease with persistent estrus, representing an estrogen-dominant condition. Herein, we report that fluctuations seen in the vaginal microflora in cyclic rats were not observed in PCO rats with persistent estrus. The vaginal-cervical mucosa of PCO rats showed numerous adherent bacteria by scanning electron microscopy, similar to that seen in proestrus and estrus rats, but unlike the diestrus rats in which fewer organisms adhered to the mucosa. Administration of human chorionic gonadotropin induced ovulation in PCO rats, which was associated with a significant decrease in serum estradiol, an increase in progesterone, and a significant decrease in the estradiol/progesterone ratio compared with baseline values (P < 0.01). This also resulted in an influx of leukocytes in the vagina with a significant decrease in vaginal anaerobic as well as aerobic bacterial flora. These data demonstrate that loss of cyclic ovarian activity in PCO rats with persistent estrus causes increased bacterial colonization of the vaginal-cervical mucosa, and the ovarian hormones appear to modulate the colonization of bacteria in the lower genital tract.