de Boer Melvin, Heuer Cord, Hussein Hassan, McDougall Scott
Cognosco, Anexa Animal Health, Morrinsville 3300, New Zealand; Epicentre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North 4442, New Zealand.
Epicentre, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North 4442, New Zealand.
J Dairy Sci. 2015 Jul;98(7):4427-38. doi: 10.3168/jds.2014-8890. Epub 2015 Apr 29.
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.
采用肉汤微量稀释法测定了9种抗菌药物对2种常见牛子宫内细菌病原体（大肠杆菌，n = 209；化脓隐秘杆菌，n = 35）分离株的最低抑菌浓度（MIC）。使用细胞刷技术从7个牛群产后的奶牛中分离出这些菌株。最初通过表型技术鉴定病原体。此外，采用聚合酶链反应（PCR）确认化脓隐秘杆菌分离株的身份，并将大肠杆菌分离株分类为系统发育组A、B1、B2和D。大肠杆菌对氨苄西林、头孢呋辛、头孢匹林和土霉素，以及化脓隐秘杆菌对土霉素的最低抑菌浓度超过已公布的切点或MIC的双峰分布表明可能存在抗菌药物耐药性。在所测试的抗菌药物中，替卡西林/克拉维酸、头孢噻呋和恩诺沙星对这2种病原体的MIC最低。发现某些抗菌药物的MIC在牛群、年龄、品种和大肠杆菌系统发育组之间存在差异。产后23天时，分离出的土霉素MIC≥8μg/mL的大肠杆菌与MIC<8μg/mL的分离株相比，在开始配种后6周内怀孕的概率较低（相对风险=0.66）。测定了来自新西兰奶牛的子宫病原体分离株的最低抑菌浓度。然而，由于缺乏流行病学或临床解释标准，这些MIC的解释仍不明确。需要进一步研究来确定解释标准，包括测定抗菌药物的药代动力学和药效学特征。
