Agriculture and Agri-Food Canada, Lacombe Research Centre, 6000 C & E Trail Lacombe, Alberta, Canada T4L 1W1.
Lett Appl Microbiol. 2010 Mar;50(3):320-6. doi: 10.1111/j.1472-765X.2010.02798.x. Epub 2010 Jan 20.
To characterize antimicrobial resistance (AMR) and determine the seasonal prevalence of Escherichia coli O157:H7 isolated from commercial feedlots.
Escherichia coli O157:H7 were isolated from faecal and oral samples collected at monthly intervals from three commercial feedlots over a 12-month period. A total of 240 isolates were characterized using pulsed-field gel electrophoresis (PFGE) technique. A subset of 205 isolates was analysed for AMR using Sensititre system and AMR genes (tet, sul and str) by PCR. Seven PFGE clusters (>or=90% Dice similarity) were identified, and two clusters common to all three feedlots were recovered year-round. The majority of isolates (60%) were susceptible to all antimicrobials and were closely related (P < 0.001), whereas isolates with unique AMR patterns were not related. The prevalences of AMR from feedlots A, B and C were 69%, 1% and 38%, respectively. Resistance to tetracycline (69%) and sulfisoxazole (68%) was more prevalent in feedlot A than other two feedlots. The presence of strA and strB genes was linked in the majority of isolates, and tet(A) and tet(B), and sul1 and sul2 genes were present individually. Escherichia coli O157:H7 were genetically diverse during summer and fall, and strains from winter and spring months were more closely related.
Antimicrobial resistance was more common in E. coli O157:H7 obtained from two of the three commercial feedlots, and the phenotypic expression of resistance was correlated with the presence of resistant genes. A highly diverse E. coli O157:H7 population was found during summer and fall seasons.
Information would help understanding the dynamics of AMR in E. coli O157:H7 from commercial feedlots.
描述抗微生物药物耐药性（AMR）并确定从商业饲养场分离出的大肠杆菌 O157：H7 的季节性流行情况。
在 12 个月的时间内，每月从三个商业饲养场收集粪便和口腔样本，从中分离出大肠杆菌 O157：H7。使用脉冲场凝胶电泳（PFGE）技术对 240 株分离株进行了特征描述。使用 Sensititre 系统和 PCR 分析了 205 株分离株的 AMR 基因（tet、sul 和 str）。鉴定了 7 个>或=90% Dice 相似性的 PFGE 簇，并且从三个饲养场全年都恢复了两个共同的簇。大多数分离株（60%）对所有抗菌药物均敏感且密切相关（P < 0.001），而具有独特 AMR 模式的分离株则没有关系。A、B 和 C 饲养场的 AMR 流行率分别为 69%、1%和 38%。与其他两个饲养场相比，A 饲养场的四环素（69%）和磺胺甲噁唑（68%）耐药率更高。大多数分离株中存在 strA 和 strB 基因，tet(A)和 tet(B)以及 sul1 和 sul2 基因则分别存在。大肠杆菌 O157：H7 在夏季和秋季的遗传多样性较高，而冬季和春季的菌株则更为相似。
从三个商业饲养场中的两个饲养场获得的大肠杆菌 O157：H7 中，抗微生物药物耐药性更为常见，并且耐药表型与耐药基因的存在相关。在夏季和秋季发现了高度多样化的大肠杆菌 O157：H7 种群。
该信息将有助于了解商业饲养场中大肠杆菌 O157：H7 的 AMR 动态。
