养猪场源致泻大肠埃希菌毒力基因和致病型研究

Pathotype and virulence genes of diarrheogenic Escherichia coli isolated from pig farms

目的了解养猪场源致泻大肠埃希菌(DEC)毒力基因及致病型分布情况,为从猪肉生产源头防控该菌引发的食源性疾病提供参考数据。方法采用多重荧光实时定量聚合酶链式反应(PCR)检测分离自12个养猪场的生猪、养殖环境和养殖工人的大肠埃希菌毒力基因,鉴定DEC的致病型。结果 985株分离自养猪场的大肠埃希菌中,DEC占比28.83%(284/985),其中肠道聚集性大肠埃希菌(EAEC)225株(22.84%,225/985)、产肠毒素大肠埃希菌(ETEC)14株(1.42%,14/985)、肠道致病性大肠埃希菌(EPEC)12株(1.22%,12/985)、肠道出血性大肠埃希菌(EHEC)10株(1.02%,10/985)、肠道侵袭性大肠埃希菌(EIEC)9株(0.91%,9/985)、EHEC-ETEC杂交型菌13株(1.32%,13/985)以及EPEC-ETEC杂交型菌1株(0.10%,1/985)。1株分离自养殖工人鼻拭子的大肠埃希菌为EHEC-ETEC杂交型菌株,同时在该养猪场的生猪鼻拭子和粪便中也检测到同样毒力基因型的菌株。猪育肥前期DEC污染率高于猪育肥后期,差异有统计学意义(χ^(2)=1.10,P<0.05)。结论养猪场DEC污染率较高,提示应加强养猪场致病菌检测,从养殖源头防控DEC污染猪肉生产链,减少食源性疾病及人畜共患病的发生。

Objective To investigate the distribution of virulence genes and pathotypes of diarrheogenic Escherichia coli(DEC) from pig farms, providing reference data for prevention and control of foodborne diseases caused by the bacteria from the pork production industry. Methods The virulence genes of Escherichia coli(E.coli), isolated from 12 pig farms, were detected by multiplex real-time quantitative polymerase chain reaction(PCR). Results Among 985 E.coli isolated from pig farms, DEC accounted for 28.83%(284/985), including 225 enteroaggregative E.coli(EAEC, 22.84%, 225/985), 14 enterotoxigenic E.coli(ETEC, 1.42%, 14/985), 12 enteropathogenic E.coli(EPEC, 1.22%, 12/985), 10 enterohemorrhagic E.coli(EHEC, 1.02%, 10/985), 9 enteroinvasive E.coli(EIEC, 0.91%, 9/985), 13 hybrid EHEC-ETEC(1.32%, 13/985), and 1 hybrid EPEC-ETEC(0.10%, 1/985). Among all those strains, one from the nose swab of a breeder had the same EHEC-ETEC virulence genotype as those positive samples detected in pig nose swab and feces. It was also found that the contamination rate of DEC in early fattening stage was significantly higher than that in late fattening stage(χ^(2)=1.10, P<0.05). Conclusion The contamination rate of DEC in pig farms was high. It is suggested that we should strengthen the detection of pathogenic bacteria in pig farms, prevent and control the DEC contamination from the source of breeding in pigs, and reduce the occurrence of foodborne diseases and zoonoses.