The owner of the stud dog may require vaginal culture of the bitch before mating. It must be recognized that the vagina is not sterile (Table 9-1). Semen is not sterile either, so if the owner of the male insists on a culture of the bitch, it is not untoward for the owner of the bitch to insist on a culture of the male. With either gender, a positive culture result does not mean anything in and of itself. A culture result can be considered significant only if there is moderate to heavy growth of one or two organisms. Mycoplasma culture is especially difficult to interpret because many laboratories will not give an idea of quantity when growth is reported. To treat all bitches with antibiotics when bred is not beneficial to the bitch or to the general population. It encourages development of bacteria that are resistant to antibiotics and, when therapy is concluded, allows a rebound of growth of organisms within the vagina.

Table 9-1 Normal Bacterial Flora of the Vagina of the Bitch

Escherichia coli	Klebsiella spp.
Streptococcus spp.	Haemophilus spp.
Pasteurella spp.	Moraxella spp.
Staphylococcus spp.	Flavobacterium
Bacillus spp.	Pseudomonas spp.
Enterococcus spp.	Mycoplasma spp.
Proteus spp.

If vaginal culture is to be performed before breeding, the following principles should be followed:

• A negative vaginal culture should neither be required nor expected. The vagina is not sterile.

• The culture sample should be collected during early proestrus using a long, guarded swab if possible (Figure 9-1). The bloody discharge of heat originates in the uterus so culture during proestrus may allow identification of a uterine infection. Culture early in proestrus allows time for the culture and sensitivity to be performed and antibiotic therapy instituted before breeding at that cycle.

• Antibiotics should be administered only if the culture result is significant. Antibiotics should be administered at least until the onset of diestrus and may be given until the time of pregnancy diagnosis, at midgestation.

Figure 9-1 Long guarded culture swab for vaginal culture during proestrus.

(Courtesy Michelle Mero Reidel.)

II. VAGINAL CYTOLOGY

Cells are easily collected from the vagina of the bitch. Because the vagina is not sterile, a nonsterile swab can be used (Figure 9-2). The swab is moistened with water and introduced into the vaginal vault, cells are gently collected from the ceiling of the vagina, and the swab is withdrawn. The swab is rolled over a glass slide, and the slide is allowed to air-dry. The slide is stained and examined under the light microscope (Figure 9-3). Although individuals may interpret the types of cells present differently, there is no significant variation in management recommended for that dog. Still it is best to have all the vaginal cytology slides for a given bitch during a given estrus read by one person whenever possible.

Figure 9-2 Nonsterile swabs suitable for collection of a vaginal cytology specimen.

Figure 9-3 Collection of a vaginal cytology specimen.

Under the influence of the hormone estrogen, the cells of the vagina are stimulated to divide. As they divide and move farther and farther from the blood supply, the cells nearest the lumen, or opening, of the vagina die (Figure 9-4). These dead cells are called cornified or keratinized cells. As the bitch starts to secrete significant amounts of estrogen during proestrus, the population of collected cells changes. Evaluation of the percentage of cornified cells present on a vaginal swab gives a ballpark idea of what is happening in the dog’s cycle. Vaginal cytology alone cannot be used to determine optimal breeding day in the bitch.