Effect of treatment with two intravaginal inserts on the uterine and vaginal microflora of early postpartum beef cows.

OBJECTIVE: To describe the bacterial species found within the uterus and vagina of early postpartum (10 to 20 d) beef cows treated for 14 d with (i) two intravaginal (CIDR-B) progesterone releasing inserts (C-P4; n=31); (ii) two identical but blank inserts (C-BL; n=15); (iii) untreated controls (CON; n=15). It was hypothesised that due to the locally immunosuppressive effects of progesterone on the uterus, the bacterial microflora of C-P4 would be altered by this treatment in contrast to CON and C-BL. PROCEDURE: Cows were enrolled at two intervals 7 d apart. Blood samples were collected at 0, 7 and 14 d after beginning treatments for subsequent progesterone assay. A triple guarded swabbing technique was used to collect bacteriological samples from the uterus of every cow on days 0, 7 and 14 following CIDR insertion. Swabs were also collected from the inserts and vagina of every cow on day 14. Due to the small sample sizes, only descriptive statistics were generated.
RESULTS: Plasma progesterone levels were maintained at mid-luteal phase concentrations by the intravaginal progesterone releasing inserts (C-P4: 4.2 +/- 0.4 ng/mL at 7 d; 3.6 +/- 0.2 ng/mL at 14 d), although increased progesterone concentrations were found in 4/15 CON and 9/15 C-BL cows on day 14. Bacteria were isolated from 32/61 (52%) of all uterine samples collected at the time of insertion. Uterine and vaginal swabs from CON cows showed a marked reduction in isolates over time such that 14 d after insertion only 1/15 uterine swabs grew bacteria. In contrast, C-BL and C-P4 treated cows failed to show reductions in the number of uterine or vaginal isolates at 14 d after device insertion. Heavy growths of Pseudomonas aeruginosa and Actinomyces pyogenes were found on the intravaginal inserts from C-BL and C-P4 cows. Cows enrolled in the second week of the study that received intravaginal inserts (C-P4 + C-BL) were more likely to have Pseudomonas isolated from the uterus than those enrolled in week 1 (1/18 versus 14/28).
CONCLUSIONS: The presence of two intravaginal inserts, regardless of hormone content, substantially altered the profile of uterine and vaginal bacteria in early postpartum beef cows. It was suspected that because of the early stage at insert application, the cervix had not involuted sufficiently to provide an adequate microbial barrier to the uterus. Pseudomonas aeruginosa was the predominant species isolated from both uterine and insert cultures after 14 d of treatment but may have been a contaminant, due to the greater proportion of cows infected with it that had been enrolled in the second week of the study.