Influence of estrogen and normal flora on vaginal candidiasis in the rat.

The vaginal epithelium of randomly bred albino rats normally does not contain yeast. This study demonstrated that estrogen-primed, castrated rats could be colonized by Candida albicans following intravaginal challenge, whereas rats not treated with estrogen remained resistant to colonization. The bacteriologic conditions of the vagina were also studied in yeast-colonized and non-yeast-colonized rats. No evidence of bacterial interference with yeast colonization was obtained from this study since the vaginal flora of the estrogen-treated, yeast-colonized rats was more abundant and diverse than that of the non-estrogen-treated rats, which were resistant to yeast colonization. Scanning electron microscopy of the vaginal epithelium of yeast-colonized rats showed that C. albicans entered the mycelial phase during colonization of the vagina. It also appeared that the mycelia penetrate the cornified vaginal epithelial cells.