Tristão Luciana C S, Gonzalez Alice G M, Coutinho César A S, Cerqueira Aloysio M F, Gomes Marcos J P, Irino Kinue, Guth Beatriz E C, Andrade João R C
Departamento de Microbiologia, Imunologia e Parasitologia, Universidade do Estado do Rio de Janeiro, Av. 28 de Setembro, 87-Fundos, CEP 20551-030, Rio de Janeiro, Brazil.
Vet Microbiol. 2007 Jan 31;119(2-4):358-65. doi: 10.1016/j.vetmic.2006.09.006. Epub 2006 Sep 17.
Shiga toxin-producing Escherichia coli (STEC) strains isolated from healthy cattle (O111:NM, seven strains; O111:H8, three strains) in Brazil were studied and compared to previously characterized human strains in regard to their phenotypic and genotypic characteristics to evaluate their pathogenic potential. Most bovine STEC O111 strains were isolated from dairy calves, and strains with genotypes stx1 alone and stx1/stx2 (variant stx2) occurred in different regions. Irrespective of the stx genotype, all strains were positive for eae theta, alpha variants of tir, espA and espB, and for ler, qseA, iha, astA and efa1 genes. Only one strain was negative for EHEC-hlyA and all strains were negative for iha, saa and espP genes and for EAF and bfpA, genetic markers of EPEC. Except for the presence of stx2, bovine strains showed the same profile of putative virulence genes found among the human strains. Similar biochemical behavior was identified among the strains analysed. Two bovine STEC strains produced the localized adherence (LA) phenotype in 6-h tests with Caco-2 (human enterocyte) cells. Intimate attachment (judged by the FAS test) was found in 9 out of 10 bovine strains as it was observed for the human STEC strains. RAPD-PCR analysis showed two distinct RAPD groups among the STEC O111 strains examined. Despite the relative low frequency of STEC O111 strains recovered from cattle no differences in their pathogenic potential were observed compared to some strains isolated from human diarrhea, suggesting that healthy cattle may be a potential source of infection for humans in Brazil.
对从巴西健康牛（O111:NM，7株；O111:H8，3株）中分离出的产志贺毒素大肠杆菌（STEC）菌株进行了研究，并就其表型和基因型特征与先前鉴定的人类菌株进行比较，以评估它们的致病潜力。大多数牛源STEC O111菌株是从奶牛犊中分离出来的，stx1单基因型和stx1/stx2（stx2变体）菌株出现在不同地区。无论stx基因型如何，所有菌株的eae theta、tir的α变体、espA和espB以及ler、qseA、iha、astA和efa1基因均呈阳性。只有一株菌株的EHEC-hlyA呈阴性，所有菌株的iha、saa和espP基因以及EAF和bfpA（肠致病性大肠杆菌的遗传标记）均呈阴性。除了存在stx2外，牛源菌株显示出与人类菌株中发现的假定毒力基因相同的谱型。在所分析的菌株中鉴定出了相似的生化行为。在与Caco-2（人肠上皮细胞）细胞进行的6小时试验中，两株牛源STEC菌株产生了局部黏附（LA）表型。在10株牛源菌株中有9株发现了紧密附着（通过FAS试验判断），人类STEC菌株也观察到了这种情况。RAPD-PCR分析显示，在所检测的STEC O111菌株中存在两个不同的RAPD组。尽管从牛中分离出的STEC O111菌株频率相对较低，但与从人类腹泻中分离出的一些菌株相比，未观察到它们致病潜力的差异，这表明健康牛可能是巴西人类感染的潜在来源。
