Cobbold R, Desmarchelier P
Department of Microbiology and Parasitology, University of Queensland, Qld 4072, St. Lucia, Australia.
Vet Microbiol. 2001 Apr 19;79(4):323-35. doi: 10.1016/s0378-1135(00)00366-7.
A total of 136 Shiga toxin-producing Escherichia coli (STEC) isolated during a longitudinal survey of three Australian dairy farms were examined to determine their virulence factors, serotype and genomic relationships. This study aimed to assess the potential of these STEC to cause disease in humans and to analyse the on-farm ecology of STEC. Virulence factors (stx, eae, ehxA) were used as determinants of potential to be enterohaemorrhagic E. coli (EHEC) and were examined using polymerase chain reaction (PCR). Among the cattle groups tested, calves, both before and during weaning, shed the most putative EHEC and were the main source of serotypes commonly associated with human disease. E. coli O157:H7 and E. coli O26:H11 represented 9.4 and 7.8% of cattle STEC isolates respectively, with other putative EHEC serotypes reported for the first time from cattle. Based on serotype and virulence factors, 20% of STEC were putative EHEC. Pulsed-field gel electrophoresis (PFGE) was used to compare the genomic profiles of STEC from dairy farms. Isolates common to cattle and the farm environment were identified. Multiple strains of STEC with high clonal turnover were detected in the faeces of cattle, and isolates appeared to be specific to individual farms. To fully assess the pre-slaughter EHEC risk factors on-farm, examination of STEC virulence is as important as determination of STEC prevalence.
在对澳大利亚三个奶牛场进行的一项纵向调查中，共检测了136株产志贺毒素大肠杆菌（STEC），以确定它们的毒力因子、血清型和基因组关系。本研究旨在评估这些STEC导致人类疾病的可能性，并分析STEC在农场中的生态情况。毒力因子（stx、eae、ehxA）被用作潜在肠出血性大肠杆菌（EHEC）的决定因素，并通过聚合酶链反应（PCR）进行检测。在测试的牛群中，断奶前和断奶期间的犊牛排出的疑似EHEC最多，是与人类疾病常见血清型的主要来源。大肠杆菌O15 7:H7和大肠杆菌O26:H11分别占牛STEC分离株的9.4%和7.8%，其他疑似EHEC血清型首次从牛中报道。根据血清型和毒力因子，20%的STEC为疑似EHEC。采用脉冲场凝胶电泳（PFGE）比较奶牛场STEC的基因组图谱。确定了牛和农场环境中常见的分离株。在牛粪中检测到多株具有高克隆周转率的STEC，并且分离株似乎对各个农场具有特异性。为了全面评估农场屠宰前EHEC的风险因素，检测STEC毒力与确定STEC流行率同样重要。
