甘肃省食源性单核细胞增生李斯特菌耐药性和基因组特征研究

Study on antimicrobial resistance and genomic characterization of foodborne Listeria monocytogenes strains in Gansu Province

目的分析甘肃省市售食品中分离的25株单核细胞增生李斯特菌耐药性和基因组特征,为单核细胞增生李斯特菌引起的食源性疾病的防控提供依据。方法以2021—2022年甘肃省市售食品中分离的25株单核细胞增生李斯特菌为研究对象,采用肉汤微量稀释法检测菌株对8种抗菌药物的敏感性,并对菌株进行血清分型和全基因组测序,分析其系统发育谱系、CC型、ST型、血清型、耐药表型及基因、毒力基因、抗性基因、系统发生关系。结果25株单核细胞增生李斯特菌分属谱系Ⅰ、谱系Ⅱ,以谱系Ⅱ为主,共21株(84.0%)。血清型以1/2a为主,共14株(56.0%),分属10个CC型,其中CC9、CC8和CC121为优势CC型,共占56.0%(14株),发现一个新的ST型,即ST3142。仅1株单核细胞增生李斯特菌耐药(4.0%,1/25),为复方磺胺甲恶唑、红霉素、四环素和环丙沙星多重耐药株,本研究菌株耐药表型与耐药基因的携带情况基本一致。25株单核细胞增生李斯特菌均携带LIPI-1和内化素基因,未发现携带LIPI-3的菌株,仅2株ST87型菌株携带LIPI-4。16株菌(64.0%)携带SSI-1,5株ST121携带SSI-2。68.0%(17/25)的菌株inlA基因发生了提前终止(PMSC)。核心基因组多位点序列分型分析能将不同谱系、血清群和CC型的菌株明显分开,25株菌共分为10个亚群,与CC型保持一致。结论甘肃省市售食品中25株单核细胞增生李斯特菌呈现遗传进化多样性,耐药基因及表型均表现出低耐药率,且携带的毒力基因丰富。

Objective To analyze the drug resistance and genomic characteristics of 25 strains of Listeria monocytogenes isolated from food products sold in Gansu Province and provide a basis for the prevention and control of foodborne diseases caused by L.monocytogenes.Methods The 25 L.monocytogenes isolated from commercial food in Gansu Province from 2021 to 2022 were collected as research subjects.All 25 strains were performed for antimicrobial susceptibility testing to 8 kinds of antibiotics,serum agglutination and sequenced the whole genome.the lineage,CC type,ST type,serotype,drug resistance phenotype and genes,virulence gene,resistance gene,phylogenetic relationship.Results The 25 L.monocytogenes strains were subtypes as lineage I and lineageⅡ,with lineageⅡbeing the dominated lineage(84.0%,21/25).The serotype 1/2a was mainly detected(56.0%,14/25).The 25 L.monocytogenes strains were found to belong to 10 CCs,with CC9,CC8 and CC121 the dominant(56.0%,14/25),discovered a new ST type,ST3142.Only one of the 25 L.monocytogenes strains was drug resistant(4.0%,1/25),multiple drug resistant to trimethoprim/sulfamethoxazole,erythromycin,tetracycline and ciprofloxacin.The drug resistance phenotype was consistent with the carrying status of drug resistance genes.All 25 strains of L.monocytogenes carried LIPI-1 and internalin genes,no strains carrying LIPI-3 were found,and only 2 ST87 strains carried LIPI-4.16 strains(64.0%,16/25)carried SSI-1,and 3 ST121 strains carried SSI-2.68.0%(17/25)of the strains had premature stop codons(PMSC)of the inlA gene.The core genome multilocus sequence typing method could clearly distinguish strains of different lineages,serotypes,and CC types.The 25 L.monocytogenes stains were divided into 10 subgroups,which were consistent with their CC type.Conclusion The predominant L.monocytogenes strains in commercial food in Gansu Province exhibited genetic evolutionary diversity,with low resistance rates in both resistance genes and phenotypes,and carried abundant virulence genes.