Changes in the aerobic vaginal bacterial mucous load and assessment of the susceptibility to antibiotics after treatment with intravaginal sponges in anestrous ewes

The aim of the study was to assess changes in the aerobic vaginal bacteria mucous load at different times following treatment with intravaginal sponges and evaluate the antibiotic susceptibility of bacteria in vitro. Intravaginal sponges impregnated with 60 mg medroxy-progesterone acetate were inserted in 22 Corriedale ewes for a period of 5 days (n = 6), 9 days (n=8) or 13 days (n = 8), respectively, during the non-breeding season. At sponge withdrawal, all ewes received 350 IU eCG im. Bacterial counts and antibiotic susceptibility studies were performed on the vaginal mucus samples obtained before the introduction of the sponges, at sponge withdrawal, 24 h following sponge withdrawal, and on the day of estrus in the three treatment groups. Nine additional ewes without pretreatment with intravaginal sponges (controls) were induced into estrus by means of the ram effect and their vaginal bacterial load was assessed at estrus. The total numbers of aerobic bacteria in the vaginal flow were not different between the groups at any point in time. The mean colony forming units (×103 ml−1) were 1.0±0.2 on the day of intravaginal sponge insertion, increased to 320.4±76.1 (P < 0.05) at sponge withdrawal, decreased 24 h later to 38.2±17.9 and decreased sharply (P < 0 05) to 1.2±0.4 at the day of estrus. The controls recorded 10.9±5.7 colony forming units (×103 ml−1) on the day of estrus which was not significantly different from the treated ewes. Qualitative features of the bacterial load (with respect to antibiotic resistance) changed with time, with increased numbers resistant to ampicillin and amoxycillin. There were no samples with resistant bacteria to cephalothin and gentamycin at any point in time. It was concluded that the use of intravaginal sponges increased bacterial flora in the vaginal mucus to the same degree despite being inserted for different periods. The different intervals of intravaginal sponge treatment did not affect the ability of the ewe to clear the bacteria reaching pre-insertion numbers by the day of estrus. Cephalothin and gentamycin seem to be the most effective antibiotic to prevent bacterial growth. © 2005 Elsevier B.V. All rights reserved.