Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Paroninkuja 20, FI-04920 Saarentaus, Finland.
Vet Microbiol. 2011 Jan 27;147(3-4):383-8. doi: 10.1016/j.vetmic.2010.07.011. Epub 2010 Jul 22.
The aim of this study was to identify specific phylogeny groups, virulence genes or antimicrobial resistance traits of Escherichia coli isolated in bovine mastitis associated to clinical signs, persistence of intramammary infection in the quarter and recovery from mastitis. A total of 154 E. coli isolates from bovine clinical mastitis, 144 from the acute stage and 10 from follow-up samples 3 weeks later, originating from 144 cows in 65 dairy herds in Southern Finland were investigated. Phylogeny groups and virulence genes of the isolates were determined using polymerase chain reaction, and antimicrobial susceptibility using the VetMIC™ microdilution method. In ten cows (11.8%), infection persisted, confirmed by re-isolation of the same pulsed-field gel electrophoresis type from the affected quarter at 3 weeks post-treatment. The majority of isolates, 119 (82.6%), belonged to phylogeny group A, which mainly consisted of commensal strains. Altogether 56 isolates (38.9%) had at least one virulence gene detected. Most common virulence genes detected were irp2, iucD, papC iss; genes svg, stx1, stx2, cnf1 and hlyA were not found. Combinations of virulence genes varied greatly. Forty (27.8%) of the 144 E. coli isolates showed resistance to at least one antimicrobial tested. None of the studied phylogeny groups, virulence factors or antimicrobial resistance traits was associated with clinical signs, persistence of intramammary infection or clinical recovery from mastitis. The results support the conclusion that mastitis-causing E. coli bacteria are typical commensals.
本研究旨在鉴定与临床症状、乳区持续性感染和乳腺炎恢复相关的牛乳腺炎分离的大肠杆菌的特定系统发育群、毒力基因或抗菌药物耐药特征。从芬兰南部 65 个奶牛场的 144 头奶牛的 154 株牛乳腺炎临床分离的大肠杆菌中，有 144 株来自急性阶段，10 株来自 3 周后随访样本。采用聚合酶链反应检测分离株的系统发育群和毒力基因，采用 VetMIC™微量稀释法检测抗菌药物敏感性。在 10 头奶牛（11.8%）中，感染持续存在，在治疗后 3 周从受影响的乳区重新分离到相同的脉冲场凝胶电泳型证实了这一点。大多数分离株（119 株，82.6%）属于 A 群，主要由共生株组成。共有 56 株（38.9%）检测到至少一种毒力基因。最常见的检测到的毒力基因是 irp2、iucD、papC iss；未发现 svg、stx1、stx2、cnf1 和 hlyA 基因。毒力基因的组合差异很大。在 144 株大肠杆菌分离株中，有 40 株（27.8%）至少对一种测试的抗菌药物表现出耐药性。所研究的系统发育群、毒力因子或抗菌药物耐药特征与临床症状、乳区持续性感染或乳腺炎临床恢复均无相关性。结果支持乳腺炎致大肠杆菌是典型共生菌的结论。
