食源性产志贺毒素大肠杆菌的分离及菌株特征分析

Isolation and characterization of Shiga toxin-producing Escherichia coli isolates in foods

目的了解不同食品中产志贺毒素大肠杆菌的流行情况、菌株特征及潜在致病性。方法对我国不同地区采集的355份食品样品进行产志贺毒素大肠杆菌分离鉴定,对菌株进行stx1/stx2基因分型、eae等毒力基因检测,并对菌株进行多位点序列分型(MLST)分析。结果 355份样品中44份stx2基因阳性,共分离出11株非O157产志贺毒素大肠杆菌,其中3株携带stx2a亚型,3株携带stx2e亚型,1株携带stx2b亚型,4株不能分型;5株携带ehxA、saa毒力基因,2株携带subA基因,1株携带katP基因;MLST将11株菌分为7个不同的ST型,存在与溶血性尿毒综合症患者肠出血性大肠杆菌分离株(HUS-associated enterohemorrhagic E.coli,HUSEC)及主要流行血清群产志贺毒素大肠杆菌亲缘关系较近的ST型别。结论我国食品中存在一定程度的非O157产志贺毒素大肠杆菌污染,部分菌株具有潜在致病性,应加强对食品中STEC的监测。

Objective To investigate the prevalence, molecular characteristics and potential pathogenicity of Shiga toxinproducing Escherichia coli （STEC） isolates in foods. Methods Shiga toxin-producing Escherichia coli were isolated from 355 different foods samples. The stxl/stx2 subtypes and virulent genes were detected by PCR. A multilocus sequence typing （MLST） scheme provided by E. coli MLST database was performed. Results Eleven non-O157 STEC strains were isolated from 355 foods samples with 3 isolates harboring stx2a, 3 harboring stx2e, 1 harboring stx2b and 4 untypable for stx2, ehxA and saa genes were detected in 5 isolates, 2 isolates were positive for subA gene and 1 isolate was positive for katP gene. The 11 isolates belonged to 7 different STs with 1 new allele type and 1 new ST identified. The phylogenetic analysis showed that the STEC isolates from foods had the relatively close genetic relationships with HUSEC or main serogroups STEC strains. Conclusion STEC exist in different foods which showed molecular diversity and had the potential to cause human diseases. Thus the detection and surveillance of STEC in foods should be enhanced to prevent the prevalence and outbreak of relative foodborne diseases.