Feasibility of histological scoring and colony count for evaluating infective severity in mouse vaginal candidiasis

Qualitative measurement of the infective level is relatively difficult in experimental vaginal candidiasis. Female BALB/c mice aged 8 to 10 weeks were randomly divided into E1, E2 and E0 groups, which received subcutaneous injection of 0.05 mg, 0.1 mg of estradiol benzoate or 0.1 ml soybean oil 3 days before vaginal inoculation, respectively, and hormone treatment continued every other day thereafter. Each group was further divided into infected and noninfected subgroups. The infected mice were inoculated intravaginally with 10 μl (5 × 10(4) conidia) of Candida albicans suspension, while the noninfected mice were inoculated with 10 μl phosphate-buffered saline. Direct microscopic examination, colony count and vaginal histopathology including infection degree and inflammation extent were performed at 3, 7 and 14 days post inoculation. Estrogen treatment increased the vaginal fungal burden and extent of infection and inflammation compared with the control group, and 0.3 mg/week estrogen generally induced more severe infection and inflammation than 0.15 mg/week estrogen did. Colony count peaked on day 3 and decreased remarkably after 7 days. Infection score increased gradually during the first 7 days and decreased on day 14, while inflammation extent exacerbated progressively over the course of 14 days. This study demonstrates that the modified histological scoring system might be more feasible than colony count for evaluation of infectivity and dynamic change in experimental vaginal candidiasis.