Cookson Adrian L, Hayes Christine M, Pearson Geoffrey R, Roe John M, Wales Andrew D, Woodward Martin J
*Department of Bacterial Diseases, Veterinary Laboratories Agency (Weybridge), Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, †Department of Clinical Veterinary Science and ‡Department of Pathology and Microbiology, University of Bristol, Langford, Bristol BS40 3DU.
J Med Microbiol. 2002 Dec;51(12):1041-1049. doi: 10.1099/0022-1317-51-12-1041.
Attaching and effacing (AE) lesions were observed in the caecum, proximal colon and rectum of one of four lambs experimentally inoculated at 6 weeks of age with Escherichia coli O157:H7. However, the attached bacteria did not immunostain with O157-specific antiserum. Subsequent bacteriological analysis of samples from this animal yielded two E. coli O115:H(-) strains, one from the colon (CO) and one from the rectum (RC), and those bacteria forming the AE lesions were shown to be of the O115 serogroup by immunostaining. The O115:H(-)isolates formed microcolonies and attaching and effacing lesions, as demonstrated by the fluorescence actin staining test, on HEp-2 tissue culture cells. Both isolates were confirmed by PCR to encode the epsilon (epsilon) subtype of intimin. Supernates of both O115:H(-) isolates induced cytopathic effects on Vero cell monolayers, and PCR analysis verified that both isolates encoded EAST1, CNF1 and CNF2 toxins but not Shiga-like toxins. Both isolates harboured similar sized plasmids but PCR analysis indicated that only one of the O115:H(-) isolates (CO) possessed the plasmid-associated virulence determinants ehxA and etpD. Neither strain possessed the espP, katP or bfpA plasmid-associated virulence determinants. These E. coli O115:H(-) strains exhibited a novel combination of virulence determinants and are the first isolates found to possess both CNF1 and CNF2.
在4只6周龄时经实验接种大肠杆菌O157:H7的羔羊中，有1只的盲肠、近端结肠和直肠观察到紧密黏附性（AE）损伤。然而，附着的细菌不能用O157特异性抗血清进行免疫染色。对该动物样本随后进行的细菌学分析得到了2株大肠杆菌O115:H(-)菌株，1株来自结肠（CO），1株来自直肠（RC），通过免疫染色显示形成AE损伤的细菌属于O115血清群。通过荧光肌动蛋白染色试验证明，O115:H(-)分离株在HEp-2组织培养细胞上形成微菌落并产生紧密黏附性损伤。通过PCR证实，两株分离株均编码intimin的ε（epsilon）亚型。两株O115:H(-)分离株的上清液均对Vero细胞单层诱导产生细胞病变效应，PCR分析证实两株分离株均编码EAST1、CNF1和CNF2毒素，但不编码志贺样毒素。两株分离株都含有大小相似的质粒，但PCR分析表明，只有一株O115:H(-)分离株（CO）拥有与质粒相关的毒力决定簇ehxA和etpD。两株菌株均不具有espP、katP或bfpA质粒相关毒力决定簇。这些大肠杆菌O115:H(-)菌株表现出一种新的毒力决定簇组合，是首次发现同时拥有CNF1和CNF2的分离株。
