A rat model of unilateral utero-tubo-ovarian abscess

Unilateral (utero-tubo-ovarian) abscesses were produced in rats with Bacteroides fragilis in pure culture. One horn of the rat's bicornuate uterus was ligated, and the inoculum of B. fragilis was placed in the uterine horn above the point of ligation. The 50% infecting dose (ID50) of B. fragilis was approximately 10(5) colony forming units (cfu). When harvested the abscesses contained up to 10(8) cfu of B. fragilis in pure culture as well as many white blood cells. Abscesses were 2-3 cm in length and contained 0.5-1.5 ml of purulent material. The oxidation-reduction potential (Eh) of the abscesses ranged from -230 to -323 millivolts. Abscess formation was comparable in all four phases of the estrous cycle. In rats treated with depoestradiol (to create a high-estrogen state), the rate of growth and size of the abscesses (3-5 cm in length and 2-3 ml of purulent material) were greater than in untreated rats.