Wieler L H, Tigges M, Ebel F, Schäferkordt S, Djafari S, Schlapp T, Baljer G, Chakraborty T
Institut für Hygiene und Infektionskrankheiten der Tiere, Justus-Liebig-Universität Giessen, Germany.
Vet Microbiol. 1996 Sep;52(1-2):153-64. doi: 10.1016/0378-1135(96)00058-2.
Naturally occurring enterohemolysin negative variants were observed during studies on bovine Shiga-like toxin-producing E. coli (SLTEC). Examination of three strains (413/89-1 and 332, 026:H-, and 570/89, O111:H-) and their isogenic variants (413/89-6, 332-I and 570/89-I, respectively) showed, that in each strain loss of the enterohemolytic phenotype correlated with the loss of a large plasmid ranging from 94 to 104 kb in size. The hemolysin determinant present on the 94 kb plasmid of strain 413/89-1 was cloned and discovered by DNA and N-terminal aminoacid sequence analysis to be highly homologous to the recently published EHEC-hemolysin (HlyEHEC; Schmidt et al., 1994; 1995). When a recombinant plasmid harboring this determinant was reintroduced into the enterohemolysin negative isogenic mutant 413/89-6, the enterohemolytic phenotype was restored. Southern blot hybridization analysis was used to demonstrate that the HlyEHEC is plasmid-borne in SLTEC-strains. Our cumulative data suggest that the enterohemolytic phenotype of SLTEC is encoded by the plasmid-borne HlyEHEC. These results further demonstrate the close similarity between SLTEC-isolates from bovine and human.
在对牛源产志贺样毒素大肠杆菌（SLTEC）的研究过程中，观察到了自然发生的肠溶血素阴性变体。对三株菌株（413/89 - 1和332，026:H -，以及570/89，O111:H -）及其同基因变体（分别为413/89 - 6、332 - I和570/89 - I）进行检测，结果表明，在每一株菌株中，肠溶血表型的丧失与大小在94至104 kb之间的一个大质粒的丢失相关。通过DNA和N端氨基酸序列分析，克隆并发现了菌株413/89 - 1的94 kb质粒上存在的溶血素决定簇，它与最近发表的肠出血性大肠杆菌溶血素（HlyEHEC；施密特等人，1994年；1995年）高度同源。当携带该决定簇的重组质粒被重新导入肠溶血素阴性的同基因突变体413/89 - 6中时，肠溶血表型得以恢复。Southern印迹杂交分析用于证明HlyEHEC在SLTEC菌株中是由质粒携带的。我们的累积数据表明，SLTEC的肠溶血表型由质粒携带的HlyEHEC编码。这些结果进一步证明了来自牛和人的SLTEC分离株之间的密切相似性。
