临沂市食源性单增李斯特菌分子特征分析

Molecular Characteristics Analysis of Foodborne Listeria monocytogenes in Linyi City

目的:基于全基因组测序分析临沂市食源性单增李斯特菌的毒力基因、耐药基因携带情况及分子分型特征。方法:利用测序数据对27株食源性单增李斯特菌株进行多位点序列分型、毒力基因和耐药基因分析,并构建基于cg-SNP的系统发育树。结果:27株分离菌株共分为10个ST型,其中ST121为优势型别。27株单增李斯特菌有26株菌携带磷霉素(FosX)耐药基因,占96.3%,2株菌携带四环素类(tetM)和甲氧苄氨嘧啶类(dfrG)2种耐药基因,仅有1株菌不耐药。27株菌出现两种毒力缺失,第一种是毒力岛LIPI-1缺失,缺失率为7.4%。第二种是毒力岛LIPI-2中inlF单一缺失,缺失率为40.7%。系统发育树分析显示,27株菌株距离较近,聚集于3个分支中。绝大部分菌株分离自肉制品,占74.1%(20/27)。结论:食源性单增李斯特菌存在多种耐药基因,毒力基因分布以毒力岛(LIPI-1、LIPI-2)为主,具有潜在的致病性。建议临沂市单增李斯特菌专项监测工作在牲畜肉制品的基础上,应加大对冷冻饮品及其乳制品原料、生禽肉类、水果蔬菜类样本的监管,进一步降低单增李斯特菌所致食源性疾病流行风险。

Objective:Based on whole genome sequencing,the virulence genes,drug resistance gene carriers and molecular typing characteristics of foodborne Listeria monocytogenes in Linyi city were analyzed.Method:Using sequencing data,27 foodborne single-increase Listeria monocytogenes were analyzed by multi-locus sequence typing,virulence genes and drug resistance genes,and a phylogenetic tree based on cg-SNP was constructed.Result:The 27 isolated strains were divided into 10 ST types,among which ST121 was the dominant type.Among the 27 strains of Listeria monocytogenes,26 strains carried fosfomycin(FosX)resistance genes,accounting for 96.3%,and two strains carried tetracyclines(tetM)and trimethoprim(dfrG)resistance genes,only one strain was not resistant.Two types of virulence were lost in 27 strains,the first was the virulence island LIPI-1 deletion,with a deletion rate of 7.4%.The second was a single deletion of inlF in the virulence island LIPI-2,with a deletion rate of 40.7%.Phylogenetic tree analysis showed that 27 strains were close together and clustered in 3 branches.The vast majority of the strains were isolated from meat products,accounting for 74.1%(20/27).Conclusion:There are a variety of drug resistance genes in foodborne Listeria monocytogenes,and the distribution of virulence genes is dominated by virulence islands(LIPI-1 and LIPI-2),which has potential pathogenicity.It is suggested that the special monitoring work of Listeria monocytogenes in Linyi city should be based on livestock meat products,and should increase the supervision of frozen beverages and their dairy raw materials,raw poultry meat,fruits and vegetables samples,further reducing the risk of foodborne diseases caused by Listeria monocytogenes.