Uterine Culture of the Mare

Numerous commercial guarded swabs are available that help prevent contamination by the normal microorganisms that are present at the caudal (rear) aspect of the reproductive tract (vulva, vaginal canal) as the swab is passed into the uterus through the cervix. Some of these swabs also work well to collect a microscopic sample of cells (cytology) from the lining of the uterus (endometrium).

There are considerable differences of opinion as to the best time to collect a uterine culture. During the winter when most mares are anestrus (lacking heat cycles) or transitional (lacking regular ovulating heat cycles) culturing the mare's reproductive tract is questionable. The lining of the uterus is dry and chances of collecting those bacteria that cause chronic endometritis are very low. When the mares are beginning to have regular cycles and the secretions of the uterus are increasing is probably the most meaningful time to obtain uterine cultures. Uterine cultures correlate well when there are exudates (drainage) from the infected uterus present at the cervix.

Meaningful uterine culture results depend on proper interpretation of laboratory results gained by proper technique. The veterinarian needs to know what microorganisms are present and in what quantity. Ideally, the uterine swab is streaked on a blood agar plate immediately after collection. This allows correlation of the number of organisms on the swab with the number of colonies growing on the blood agar plate. When collecting samples on the farm the swab may dry and the bacteria may be lost or if the samples are stored in transport media or nutrient broth, proliferation of a few contaminating bacteria makes quantification impossible. An indication of the number of colonies present is important to include in the laboratory report, as is the identification of the microorganism. Pure cultures are more significant than mixed ones.

Cultures of the bacteria beta Streptococcus, E. coli, Pseudomonas, Klebsiella and the yeast Monilia are considered pathogenic (disease causing). Many other species of bacteria are commonly cultured, however, most of these organisms are considered to be normal bacterial flora of the reproductive tract and they are contaminants of the uterine culture. Examination of the cells of the uterine lining that are collected at the same time the uterine culture is obtained can be very helpful as to whether significant inflammation is present. The presence of numerous white blood cells on the cytology smear from a uterine swab is highly correlated with a diagnosis of endometritis.In my opinion, the uterine culture, by itself, is not very meaningful. It is part of the complete gynecologic exam that includes a physical examination of the mare, examination of the perineum (rear end), transrectal palpation of the reproductive tract, transrectal ultrasonic examination of the reproductive tract, vaginal speculum and digital exam, uterine culture, and uterine cytology. What stallion owners want to know and what mare owners should want to know: Is my mare ready to breed and is she likely to settle when she is bred? Without a complete examination meaningful, accurate answers cannot be obtained. Talk to your veterinarian. Talk to your stallion owner. Proper preparation prevents poor performance.

Looking forward to spring!

Warmest regards, Dr. Frosty Franklin