即食食品中单核细胞增生李斯特菌的血清学分型和毒力基因分析

Serological typing and virulence-associated genes analysis of Listeria monocytogenes isolated from ready-to-eat foods

目的掌握即食食品中单核细胞增生李斯特菌(简称单增李斯特菌)的血清型、谱系和感染相关基因的分布。方法以全国食源性致病菌监测网中2007—2009年自即食食品分离的226株单增李斯特菌为研究对象,采用传统的血清学分型技术和等位基因特异性寡核苷酸PCR方法(ASO-PCR)研究其血清学分型,并采用PCR方法检测其与感染相关的基因。结果 226株单增李斯特菌血清学分型结果显示,1/2a、1/2b、1/2c、4b为主要血清型,比例分别为41.59%(94/226)、40.71%(92/226)、10.62%(24/226)和5.31%(12/226)。引起人类疾病的常见血清型1/2a、1/2b和4b菌株占87.61%(198/226)。谱系Ⅰ菌株为105株,谱系Ⅱ菌株为120株,谱系Ⅲ菌株为1株;我国绝大部分即食食品中单增李斯特菌分离株的感染相关基因缺失率较低,只有个别菌株缺失感染相关基因。结论本研究通过对分离自即食食品中的单增李斯特菌进行血清学分型、谱系分析和感染相关基因的检测,提示我国需要加强食品场所卫生管理,降低单增李斯特菌对即食食品的感染风险。

Objective To investigate the serotype,genealogy and infection-related genes of Listeria monocytogenes isolated from ready-to-eat foods. Methods Two hurdred and twenty-six Listeria monocytogenes isolated from ready-to-eat foods from 2007 to 2009 were collected from the National Foodborne Pathogen Surveillance Network. The serological typing was carried out using conventional serological typing and allele-specific oligonucleotide PCR（ ASO-PCR）. And their infection-related genes were detected by PCR. Results Among the 226 Listeria monocytogenes isolates from ready-to-eat foods,serovar 1 /2a（ 41. 59%,94 /226） and 1 /2b（ 40. 71%,92 /226） were dominant followed by serovar 1 /2c（ 10. 62%,24 /226） and 4b（ 5. 31%,12 /226）. The rate of human infection related serovar 1 /2a,1 /2b and 4b was relatively high（ 87. 61%,198 /226）,which indicated the potential risk in ready-to-eat foods. There were 105 strains of lieage I and 120 of lieage II,only one strain of lieage III. Virulence-associated genes were rarely missing in Listeria monocytogenes strains isolated from ready-to-eat foods indicating a high risk. Conclusion According to the serology and virulence genes distribution of Listeria monocytogenes isolated from ready-to-eat foods,food sanitation management should be strengthened to reduce the risk of infection.