Kaufmann M, Zweifel C, Blanco M, Blanco J E, Blanco J, Beutin L, Stephan R
Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Switzerland.
J Food Prot. 2006 Feb;69(2):260-6. doi: 10.4315/0362-028x-69.2.260.
Fecal samples from 630 slaughtered finisher pigs were examined by PCR to assess the shedding of Escherichia coli O157 (rfbE) and Shiga toxin-producing E. coli (STEC, stx). The proportion of positive samples was 7.5% for rfbE and 22% for stx. By colony hybridization, 31 E. coli O157 and 45 STEC strains were isolated, and these strains were further characterized by phenotypic and genotypic traits. Among E. coli O157 strains, 30 were sorbitol positive, 30 had an H type other than H7, and none harbored stx genes. Intimin (eae), enterohemolysin (ehxA), EAST1 (astA), and porcine A/E-associated protein (paa) were present in 10, 3, 26, and 6% of strains. Among them, one eae-gamma1-positive O157:H7 strain testing positive for ehxA and astA and two eae-alpha1-positive O157:H45 strains were classified as enteropathogenic E. coli (EPEC). The O157:H45 EPEC harbored the EAF plasmid and the bfpA gene, factors characteristic for typical EPEC. The isolated STEC strains (43 sorbitol positive) belonged to 11 O:H serotypes, including three previously reported in human STEC causing hemolytic uremic syndrome (O9:H-, O26:H-, and O103:H2). All but one strain harbored stx2e. The eae and ehxA genes, which are strongly correlated with human disease, were present in only one O103:H2 strain positive for stx1 and paa, whereas the astA gene was found more frequently (14 strains). High prevalence of STEC was found among finisher pigs, but according to the virulence factors the majority of these strains seem to be of low virulence.
通过聚合酶链反应（PCR）检测了630头屠宰育肥猪的粪便样本，以评估大肠杆菌O157（rfbE）和产志贺毒素大肠杆菌（STEC，stx）的排泄情况。rfbE阳性样本比例为7.5%，stx阳性样本比例为22%。通过菌落杂交，分离出31株大肠杆菌O157和45株STEC菌株，并通过表型和基因型特征对这些菌株进行了进一步鉴定。在大肠杆菌O157菌株中，30株山梨醇阳性，30株H型不是H7，且均未携带stx基因。intimin（eae）、肠溶血素（ehxA）、EAST1（astA）和猪A/E相关蛋白（paa）分别存在于10%、3%、26%和6%的菌株中。其中，一株eae-γ1阳性的O157:H7菌株ehxA和astA检测呈阳性，两株eae-α1阳性的O157:H45菌株被归类为肠致病性大肠杆菌（EPEC）。O157:H45 EPEC携带EAF质粒和bfpA基因，这是典型EPEC的特征性因子。分离出的STEC菌株（43株山梨醇阳性）属于11种O:H血清型，包括之前在人类STEC中报道的三种导致溶血尿毒综合征的血清型（O9:H-、O26:H-和O103:H2）。除一株外，所有菌株均携带stx2e。与人类疾病密切相关的eae和ehxA基因仅在一株stx1和paa阳性的O103:H2菌株中存在，而astA基因的出现频率更高（14株）。育肥猪中STEC的流行率较高，但根据毒力因子，这些菌株中的大多数似乎毒力较低。
