Establishment and Validation of a Mouse Bacterial Vaginosis Model

Bacterial vaginosis (BV) is a common vaginal infection without a reliable animal model. To establish a novel mouse BV model, we evaluated multiple parameters of various identified bacteria-infected mice, including Staphylococcus aureus (SA), Escherichia coli (EC), Streptococcus agalactiae, β-Hemolytic streptococcus, and Gardnerella vaginalis (GV).

Mature female KM mice were randomly allocated to a vehicle group (group A, without any treatment) and experimental groups. After vaginal secretions were harvested, experimental groups were divided into phosphate buffer solution group (PBS, group B), control group including SA, and EC with a 1:1 ratio (group C), SA, EC, and Streptococcus agalactiae with a 1:2:1 ratio group (group D), SA, EC, and β-Hemolytic streptococcus with a 1:2:1 ratio group (group E), and GV group (group F). The vaginal secretions of experimental mice were collected by flushing with 100 mL sterile PBS on days 2, 4, and 6. Vaginal secretions were examined by Gram staining, sialidase assay, ammonia test, and pH value measurement. IL-6 and IL-10 levels in mouse serum were detected by enzyme-linked immunosorbent assay. Hematoxylineosin staining and mouse cervicovaginal tissue histopathological scores were observed. The diagnostic test results were analyzed by logistic regression analysis and receiver operating characteristic curves. The Shapiro-Wilk analysis of variance, or rank-sum test, was used for normal distribution analysis. Pearson's correlation and chi-squared test determined the correlation and comparison data expressed as a percentage or frequency.

There was less severe vaginal morphology in GV-infected mice compared to other bacteria-infected mice. The sialidase assay, the ammonia test, and the pH values of vaginal secretions showed significant differences between GV-infected and uninfected mice. Serum IL-6 and IL-10 levels and vaginal histological scoring increased in other bacteria-infected mice, but GV-infected mice showed only a mildly increasing trend of IL-10 levels and vaginal histological scoring compared to control mice.

GV-infected mice showed clinical features similar to human BV infection, including vaginal anatomical and pathological indices, and biochemical and immune parameters. Serum IL-10 level has potential for use in BV diagnosis.