Molecular Characterization of Enterotoxigenic Escherichia coli Strains Isolated from Diarrheal Patients in Korea during 2003–2011

Enterotoxigenic Escherichia coli (ETEC) is one of the major causes of infectious diarrhea in developing countries. In order to characterize the molecular features of human ETEC isolates from Korea, we investigated the profiles of enterotoxin and colonization factor (CF) genes by polymerase chain reaction (PCR) and performed multilocus sequence typing (MLST) with a total of 291 ETEC strains. The specimens comprised 258 domestic strains isolated from patients who had diarrhea and were from widely separated geographic regions in Korea and 33 inflow strains isolated from travelers visiting other Asian countries. Heat-stable toxin (STh)-possessing ETEC strains were more frequent than heat-labile toxin (LT)-possessing ETEC strains in the domestic isolates, while the detection rates of both enterotoxin genes were similar in the inflow isolates. The profile of CF genes of domestic isolates was similar to that of inflow isolates and the major CF types of the strains were CS3-CS21-CS1/PCF071 and CS2-CS3-CS21. Most of these 2 CF types were detected in ETEC strains that possess both lt and sth genes. The major MLSTST types of domestic isolates were ST171 and ST955. Moreover, the 2 major CF types were usually found concomitantly with the 2 major MLST STs, ST171 and ST955. In conclusion, our genotyping results may provide useful information for guiding the development of geographically specific vaccines against human ETEC isolates.

产肠毒素大肠杆菌（Enterotoxigenic Escherichia coli, ETEC）是发展中国家感染性腹泻的主要致病原之一。为表征源自韩国的人类ETEC分离株的分子特征，本研究通过聚合酶链反应（polymerase chain reaction, PCR）检测肠毒素与定植因子（colonization factor, CF）基因谱，并对共计291株ETEC菌株开展多位点序列分型（multilocus sequence typing, MLST）。本次研究的菌株标本包含258株韩国本土分离株，均采自韩国境内不同地理区域的腹泻患者，另有33株输入性分离株，源自赴其他亚洲国家旅行的旅行者。在本土分离株中，携带耐热肠毒素（STh）的ETEC菌株占比高于携带不耐热肠毒素（LT）的菌株；而在输入性分离株中，两种肠毒素基因的检出率较为接近。本土分离株与输入性分离株的定植因子基因谱相似，菌株的主要定植因子类型为CS3-CS21-CS1/PCF071与CS2-CS3-CS21。上述两类主要定植因子大多存在于同时携带lt与sth基因的ETEC菌株中。本土分离株的主要MLST型别为ST171与ST955。此外，这两类主要定植因子通常与ST171、ST955这两种主要MLST型别伴随出现。综上，本研究的基因分型结果可为针对人类ETEC分离株的地域特异性疫苗研发提供有价值的参考信息。