Minimum inhibitory concentrations of selected antimicrobials against Escherichia coli and Trueperella pyogenes of bovine uterine origin.

Minimum inhibitory concentrations (MIC) of 9 antimicrobials for isolates of 2 common bovine intrauterine bacterial pathogens, Escherichia coli (n=209) and Trueperella pyogenes (n=35), were determined using broth microdilution methodology. The isolates were recovered from dairy cows from 7 herds postpartum using the cytobrush technique. The pathogens were initially identified using phenotypic techniques. Additionally, PCR was used to confirm the identity of T. pyogenes isolates and to categorize the E. coli isolates into phylogenetic groups A, B1, B2, and D. Minimum inhibitory concentrations in excess of published cut-points or bimodal distributions of MIC indicated potential antimicrobial resistance to ampicillin, cefuroxime, cephapirin, and oxytetracycline for E. coli, and to oxytetracycline for T. pyogenes. Of the antimicrobials tested, ticarcillin/clavulanic acid, ceftiofur, and enrofloxacin had the lowest MIC for these 2 pathogens. Differences in MIC of some antimicrobials were found between herds, age, breeds, and E. coli phylogenetic groups. Isolation of E. coli with an MIC ≥8µg/mL of oxytetracycline at 23d postpartum was associated with a lower probability of pregnancy within 6wk of commencement of breeding compared with those isolates with an MIC <8µg/mL (relative risk=0.66). Minimum inhibitory concentrations for uterine pathogens were determined for isolates from New Zealand dairy cows. However, in the absence of either epidemiological or clinical interpretive criteria, the interpretation of these MIC remains unclear. Further studies are required to define interpretative criteria, including determination of pharmacokinetic and pharmacodynamic profiles for antimicrobials.

Associations between intrauterine bacterial infection, reproductive tract inflammation, and reproductive performance in pasture-based dairy cows.

Reproductive tract bacterial infections, particularly those caused by Escherichia coli and Trueperella pyogenes, can have a negative impact on reproductive performance. It has been hypothesized that the presence of E coli early postpartum may increase the risk of isolation of T pyogenes later postpartum. The objective of the present study was to examine associations between intrauterine bacterial infections with E coli and T pyogenes and any bacterial growth (irrespective of bacterial species), purulent vaginal discharge (PVD), cytologic evidence of endometritis (an increased proportion of polymorphonuclear cells [PMNs]), and reproductive performance. Dairy cows (n = 272) from six herds were examined at Days 0 (median, 2 days in milk), 21 and 42 postpartum. From each cow two intrauterine samples were collected via triple-guarded cytobrush at Days 0 and 21. The first cytobrush was used for bacteriologic culture. Escherichia coli and T pyogenes were isolated by culture, and E coli isolates were assigned to one of four phylogenetic groups using a two-step triplex polymerase chain reaction. In addition, T pyogenes was confirmed by polymerase chain reaction. The second cytobrush was used to prepare a cytology slide. Nucleated cells (n = 200) were categorized as epithelial cells, PMNs, or macrophages. Cows were also assessed for body condition score, PVD score, the presence of a CL, and pregnancy. Statistical analysis was performed using multivariable models. There was no association between the presence of E coli at Day 0 and probability of isolation of T pyogenes 3 weeks later; however, E coli positive cows at Day 0 were more likely to be diagnosed with E coli at Day 21 (relative risk [RR] = 2.0, P < 0.01). Escherichia coli at Day 0 or T pyogenes at Day 21 increased the risk of PVD diagnosis 3 weeks later (RR = 1.9; P = 0.04 and RR = 3.0; P = 0.05, respectively). Cows with any bacterial growth at Day 21, irrespective of species, were less likely to conceive within 3 weeks after the start of the seasonal breeding program (RR = 0.8; P = 0.05). Interestingly, cows with 25% PMNs or greater at Day 0 had shorter time to pregnancy (hazard ratio = 1.32; P = 0.05). Intrauterine bacterial infection may impair reproductive performance but the presence of E coli was not associated with isolation of T pyogenes 3 weeks later. Increased endometrial flux of PMNs in cows early postpartum may be a physiological process and improve reproductive performance.

Clinical trial of treatment programs for purulent vaginal discharge in lactating dairy cattle in New Zealand.

Studies of treatment of postpartum endometritis in dairy cows indicate that prostaglandin (PGF2α) might result in similar outcomes as intrauterine antibiotics, but the effect might depend on the presence of a CL. The objective was to compare reproductive performance in cows with purulent vaginal discharge treated on the basis of having or not having a CL (CL-dependent treatment; CLdep), versus treatment of all affected cows with an intrauterine antibiotic alone. Cows (N = 756) from 36 seasonal calving dairy herds in New Zealand were enrolled on the basis of having a vaginal discharge score (VDS) ≥2 (mucus with flecks of pus or more purulent) after examination with the Metricheck device (Simcro, Hamilton, New Zealand) and ≥14 days after calving. The presence of a CL was assessed by transrectal palpation. Cows were randomly assigned within farm to be treated with an intrauterine antibiotic (0.5 g cephapirin) irrespective of CL status, or treated with PGF2α if a CL was present and cephapirin if a CL was not present (CLdep). The VDS was reassessed 14 days later. Cows were bred using standard practices and pregnancy was tested to define the date of conception. The proportion of cows clinically cured (i.e., with a VDS ≤1 at reexamination) did not differ between treatment groups (0.82 ± 0.03 vs. 0.80 ± 0.03) for the group of cows treated with an intrauterine antibiotic irrespective of CL status and the CLdep groups, respectively (P = 0.66). The proportions of cows submitted for AI by 21 days into the breeding program, pregnant to first breeding, pregnant by 42 days into the breeding program, and at the end of the breeding program, and the interval from the start of the mating program to pregnancy did not differ among treatment groups. Cows that had positive VDS (i.e., >1) at Day 14 after treatment had lower proportions of conception and pregnancy than those with lower (<2) VDS. A treatment protocol in which cows with purulent vaginal discharge with a palpable CL were treated with PGF2α and those without a CL with intrauterine cephapirin resulted in reproductive performance that was not inferior to treating all cows with an intrauterine antibiotic.

Prevalence and genotypes of Giardia duodenalis in dairy and beef cattle in farms around Charlottetown, Prince Edward Island, Canada.

Prevalence of Giardia duodenalis in dairy and beef cattle on farms around Charlottetown, Prince Edward Island (Canada) was determined by analyzing feces using direct immunofluorescence antibody microscopy. Genotypes were determined by 16S-rRNA sequencing. Fecal samples (n = 892) were collected from adult cattle in dairy tie-stall, dairy free-stall, and beef herds (10 herds each), and from calves (n = 183) from 11 dairy farms. Prevalence rates were 38% and 51% in cows and calves, respectively. Giardia duodenalis was present in all dairy herds, in 9/10 beef herds and in calves from 10/11 herds examined. Prevalence rates were 40% and 41% for cows in tie- and free-stall herds, respectively, and 27% for beef cows. Zoonotic Assemblage A was found in 12.2% of calves concomitantly infected with Assemblage E. All successfully sequenced samples (114/128) from cows corresponded to Assemblage E. Giardia duodenalis is highly prevalent in cattle herds in Prince Edward Island and Assemblage A in calves is a potential public health concern.