Wilson J B, McEwen S A, Clarke R C, Leslie K E, Wilson R A, Waltner-Toews D, Gyles C L
Department of Population Medicine, Ontario Veterinary College, University of Guelph, Canada.
Epidemiol Infect. 1992 Jun;108(3):423-39. doi: 10.1017/s0950268800049931.
Faecal swabs obtained from a random sample of 1131 cows and 659 calves on 100 southern Ontario dairy farms were examined for verocytotoxigenic Escherichia coli (VTEC) using a Vero cell assay. Five isolates from each positive culture were tested similarly. Positive colonies were examined with DNA probes for Shiga-like toxin I (SLT-I) and SLT-II sequences. Probe-negative colonies were tested for neutralization of verocytotoxicity using anti-SLT-I and anti-SLT-IIv antisera. Colonies showing no neutralization response were examined in a polymerase chain reaction procedure. Colonies positive by any test were confirmed to be E. coli biochemically, serotyped, biotyped and tested for antimicrobial resistance. Faecal culture supernatants which were positive in the Vero cell assay, but culture negative, were examined using the neutralization assay. Animals were classified positive by faecal culture supernatant or by positive VTEC isolate. The prevalence rates of VTEC infection in cows and calves were estimated to be 9.5 and 24.7%, respectively. The proportion of animals infected on each farm ranged from 0 to 60% for cows and 0 to 100% for calves. Of 206 VTEC isolates identified, few were of serotypes which have been isolated from humans and none were E. coli O 157.H7.
从安大略省南部100个奶牛场随机抽取1131头奶牛和659头小牛的粪便拭子，采用Vero细胞分析法检测产志贺毒素大肠杆菌（VTEC）。对每份阳性培养物中的5个分离株进行同样检测。用DNA探针检测阳性菌落的志贺样毒素I（SLT-I）和SLT-II序列。对探针阴性菌落用抗SLT-I和抗SLT-IIv抗血清检测其对志贺毒素毒性的中和作用。对无中和反应的菌落进行聚合酶链反应检测。对任何检测呈阳性的菌落进行生化鉴定，确定为大肠杆菌，进行血清分型、生物分型并检测其抗菌药物耐药性。对Vero细胞分析法呈阳性但培养呈阴性的粪便培养上清液进行中和试验检测。根据粪便培养上清液或VTEC阳性分离株将动物分类为阳性。估计奶牛和小牛中VTEC感染的患病率分别为9.5%和24.7%。每个农场感染动物的比例，奶牛为0%至60%，小牛为0%至100%。在鉴定出的206株VTEC分离株中，很少有从人类分离出的血清型，且没有一株是大肠杆菌O157.H7。
