Streptomycin-resistant Escherichia coli as a marker of vulvovestibular contamination of endometrial culture swabs in the mare.

To investigate the vulvovestibular contamination of endometrial culture swabs in the mare, a liquid culture of a streptomycin-resistant strain of Escherichia coli was applied to the vulvovestibular area of mares and used as a marker of contamination of endometrial culture swabs. Prior to taking endometrial swabs, the perineal area was washed with soap, rinsed with water, and dried. Endometrial culture swabs were taken from mares that were in anestrus or diestrus and from mares that were in estrus. When a manual transvaginal swabbing technique was used, 22 of 24 endometrial swab specimens from 12 mares were contaminated with the experimental bacterial strain; culture of only one endometrial swab yielded more than nine colonies. When a speculum approach was employed, three of 12 swab specimens from 12 mares yielded between one and three colonies. The stage of cycle had no effect on the extent of contamination, but the proportion of positive cultures was significantly smaller when swabs were taken via a vaginal speculum approach, compared to a manual transvaginal approach. Complete preclusion of vulvovestibular contamination of endometrial swab specimens was not achieved; however, fewer than ten colonies can be expected even in mares in which the vulvovestibular area has been thoroughly contaminated with a broth culture, provided that the perineal area is adequately cleaned prior to swabbing.