Whittam T S, Wolfe M L, Wachsmuth I K, Orskov F, Orskov I, Wilson R A
Department of Biology, Pennsylvania State University, University Park 16802.
Infect Immun. 1993 May;61(5):1619-29. doi: 10.1128/iai.61.5.1619-1629.1993.
The genetic relationships among 1,300 isolates of Escherichia coli representing 16 serotypes associated with enteric disease, including O157:H7 strains recovered from patients with hemorrhagic colitis and hemolytic uremic syndrome and O26:H11, O55:H6, O55:H7, O111:H2, and O128:H2 strains, many of which were isolated originally from infants with diarrhea, were estimated from allelic variation among 20 enzyme-encoding genes detected by multilocus enzyme electrophoresis. Multiple electrophoretic types were observed among isolates of each serotype, with isolates of the same O serogroup differing on average at 28% of the enzyme loci. Comparisons of the multilocus enzyme profiles revealed that 72% of the isolates belong to 15 major electrophoretic types, each of which corresponds to a bacterial clone with a wide geographic distribution. Genetically, the O157:H7 clone is most closely related to a clone of O55:H7 strains that has long been associated with worldwide outbreaks of infantile diarrhea. We propose that the new pathogen emerged when an O55:H7-like progenitor, already possessing a mechanism for adherence to intestinal cells, acquired secondary virulence factors (Shiga-like cytotoxins and plasmid-encoded adhesins) via horizontal transfer and recombination.
对1300株大肠杆菌的遗传关系进行了评估，这些菌株代表了16种与肠道疾病相关的血清型，包括从出血性结肠炎和溶血尿毒综合征患者中分离出的O157:H7菌株，以及O26:H11、O55:H6、O55:H7、O111:H2和O128:H2菌株，其中许多最初是从腹泻婴儿中分离出来的。通过多位点酶电泳检测20个编码酶的基因中的等位基因变异来估计它们的遗传关系。在每种血清型的分离株中观察到多种电泳类型，同一O血清群的分离株平均在28%的酶位点上存在差异。多位点酶谱比较显示，72%的分离株属于15种主要电泳类型，每种类型对应一个具有广泛地理分布的细菌克隆。从基因角度来看，O157:H7克隆与长期以来与全球婴儿腹泻暴发相关的O55:H7菌株克隆关系最为密切。我们提出，当一个已经具有肠道细胞黏附机制的O55:H7样祖先通过水平转移和重组获得次级毒力因子（志贺样毒素和质粒编码黏附素）时，新的病原体就出现了。
