Evaluating a murine model of endometritis using uterine isolates of Escherichia coli from postpartum buffalo

Ascending infection of the uterus with Gram-negative bacteria is responsible for postpartum endometritis in cattle and buffalo and can adversely affect fertility. Development of a laboratory animal model for bovine endometritis would facilitate the understanding of the pathogenesis as it is difficult to conduct controlled experimentation in the native host. In the present study, 30 virgin Swiss Albino mice (5-8 weeks old) were used to evaluate the pathogenic potential of Escherichia coli, isolated from the normally calved postpartum buffalo to induce endometritis. Mice in the diestrus phase of the estrous cycle were randomly allotted to one of the following four intravaginal inoculation (100 μL) treatments: EG (experimental group)-1: sterile normal saline; EG-2, -3 and -4: E. coli@ 1.5 × 104, 105 and 106 CFU/ml, respectively. The animals were then scarified 36 h post-inoculation to study gross and microscopical lesions. Gross changes were confined to EG-4. Acute endometritis was recorded in 50% of the EG-3 and 66.7% of the EG-4. The rate of acute endometritis development was significantly higher in EG-4 (P<0.05) as compared to the other groups. The present study demonstrated that the animal model for bubaline endometritis can be developed in mice by intravaginal inoculation of E. coli@ 1.5 × 106 CFU/ml at diestrus. Ease of intravaginal inoculation, apparent absence of systemic involvement and high infective rate are the advantages of the model over other studies.