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12 Uterine Culture Collection: Swab/Brush

John J. Dascanio

School of Veterinary Medicine, Texas Tech University, USA

Introduction

Culture of the uterus is performed as part of the routine mare breeding soundness examination. It is also performed as part of an infertility workup, or upon request by a stallion owner prior to breeding, or as surveillance for disease. Culture may be performed via a standard uterine culture swab, from secretions obtained from a uterine brush, from a uterine biopsy, or from fluid obtained from a low volume uterine lavage.

The method for performing a uterine culture depends on a number of factors, such as cost, time to perform the procedure, and availability of equipment. Generally, a guarded or double‐guarded swab or brush is routinely used to obtain a sample for culture, while a low volume uterine lavage would be indicated for an infertility workup in a problem mare or in a mare that is suspected of an infection, but has had a negative uterine swab/brush. With persistent or chronic infections, culture of a uterine biopsy may be warranted.

The best time to perform a uterine culture may be debatable, but is most often performed in early estrus. Cultures may be performed in diestrus, but prostaglandins should be administered after the collection procedure to lyse any luteal tissue and bring the mare into estrus, so that any contaminants introduced during the procedure may be eliminated.

Culture swabs should be immediately plated onto blood agar or other appropriate microbial culture media. If a culture swab is transported to a laboratory, it should be held at refrigerator temperature to prevent overgrowth of contaminants.

Equipment and Supplies

Tail wrap, tail rope, non‐irritant soap, roll cotton, stainless steel bucket, disposable liner for bucket, paper towels, sterile lubricant, sterile obstetrical sleeve, guarded culture device (Kalayjian swab, single‐guarded (Figure 12.1); McCullough swab, double‐guarded (Figure 12.2); or uterine brush, guarded (Figure 12.3)), aerobic bacterial transport device.

Technique

Remove feces from the rectum.

Place a tail wrap and tie the tail out of the way (see Chapter 4).

Clean and dry the perineum of the mare (see Chapter 3).

Place a sterile obstetrical sleeve on the arm.

Place the guarded culture device into the palm of the hand.

Place sterile lubricant on the knuckles and down the length of the sleeve being careful not to get lubricant onto the palm. If the culture device becomes inundated with lubricant, it may be more difficult to obtain a diagnostic sample.

Rub lubricant from the knuckles onto the vulva, straighten the fingers and insert through the vulva.

Using a slight rotating motion, pass the hand into the vagina so that the mid‐forearm is to about the level of the vulva. This should enable palpation of the external cervical os.Figure 12.1 Kalayjian swab in the open position.Figure 12.2 McCullough swab in the open position.

Gently insert the index finger into the external cervical os. Sometimes the os may be off center, located slightly downward, or to the left or right of center.

Pass the index finger through the cervix to the last knuckle (metacarpo‐phalangeal joint). Usually one can detect when the fingertip enters the uterine body lumen. Pass the uterine culture instrument past the inserted index finger into the uterine body. Sometimes, if the cervical canal is under the influence of progesterone and is toned, the index finger may need to be removed prior to passing the culture device. The culture instrument may need to be pointed in a slightly downward direction when being passed through the cervix due to the dependent nature of the suspended uterus within the abdomen, especially in older broodmares.

As most culture devices used today have a guard over the inserted end, the inner swab/brush is subsequently pushed forward through the cap/guard.Figure 12.3 Uterine brush in the open position.

Gently press the swab or brush in contact with the endometrium and gently rotate in one direction. It is recommended that the swab/brush be in contact with the endometrium for 10–15 seconds.

The swab/brush is retracted back inside the outer guards and then the device is removed from the mare. Care should be taken when rotating the swab as excessive motion can result in breaking of the end of the swab (Figure 12.4).

Once the culture instrument has been withdrawn from the external cervical os, a cupped hand should be placed over the device to limit vaginal contamination to the swab/brush.

The swab should be immediately plated or transferred to a transport device with media such as a CultureSwab™ (Figure 12.5). Often the outer swab guard is removed from the inner guard before extending the swab/brush into a transport device to limit contamination from the outer guard.

Figure 12.4 Tip of a uterine culture instrument broken off in the uterine lumen.

Figure 12.5 Transport device for uterine cultures.

Interpretation

In mares with a dependent uterus, well over the brim of the pelvis, the swab may be subjected to the downward weight of the uterus, making breakage of the tip of the swab more likely. Breakage of the swab tip may occur particularly when the swab is rotated, thus caution should be used.

Note any discharge present on the sterile sleeve when the gloved arm is pulled from the vagina. There should not be any purulent or hemorrhagic discharge, only the lubricant and clear mucous should be present.

Ensure that the culture device is intact and that no part of the instrument was left within the mare's uterus/cervix/vagina.

Note any discharge on the tip of the culture device. It is not uncommon to see some mild hemorrhage on the culture device as it rubbed against the endometrium.

The most common pathogens of the equine uterus are Streptococcus equi subspecies zooepidemicus, Escherichia coli, Klebsiella species, Pseudomonas aeruginosa, and fungi, among others.

Heavy growth of one organism may have more significance than light growth of multiple organisms.

Uterine culture results should be correlated with uterine cytology and other reproductive findings to determine significance.