Abstract：
Listeria monocytogenes are considered to be the major foodborne pathogen worldwide. To understand the prevalence and potential risk of L. monocytogenes in retail foods, a total of 1243 retail foods in 12 food categories were sampled and screened for L. monocytogenes from 2020 to 2022 in Huzhou, China. A total of 46 out of 1234 samples were confirmed to be L. monocytogenes positive with a total rate of 3.7%. The contamination rate of seasoned raw meat (15.2%) was the highest, followed by raw poultry meat and raw livestock meat (9.9%) and salmon sashimi (9.5%). The L. monocytogenes isolates belonged to four serotypes, 1/2a,1/2b, 1/2c, and 4b, with the most prevalent serotype being 1/2a (47.9%). All isolates were grouped into 15 sequence types (STs) belonging to 14 clonal complexes (CCs) via multilocus sequence typing (MLST). The most prevalent ST was ST9/CC9 (23.9%), followed by ST3/CC3 (19.6%) and ST121/CC121 (17.4%). Notably, 11 STs were detected from ready-to-eat (RTE) foods, some of them have been verified to be strongly associated with clinical origin listeriosis cases, such as ST3, ST2, ST5, ST8, and ST87. Listeria pathogenicity islands 1 (LIPI-1) and LIPI-2 were detected in approximately all L. monocytogenes isolates, whereas the distribution of both LIPI-3 genes and LIPI-4 genes exhibited association with specific ST, with LIPI-3 in ST3 and ST288, and LIPI-4 in ST87. The strains carrying LIPI-3 and LIPI-4 virulence genes in this study were all isolated from RTE foods. Antimicrobial susceptibility tests showed that >90% of isolates were susceptible to PEN, AMP, ERY, CIP, SXT, VAN, CHL, and GEN, indicating the antibiotic treatment might be still efficient for most of the L. monocytogenes strains. However, for the three clinical first-line antibiotics (PEN, AMP, and GEN), we also observed three and four strains showing MIC values greater than the susceptibility standards for PEN and AMP, respectively, and one strain showing resistance to GEN.
摘要：
单核细胞增生李斯特菌被认为是全球主要的食源性病原体。了解零售食品中单核细胞增生李斯特菌的患病率和潜在风险，2020-2022年，湖州市12个食品类别1243种零售食品进行了单核细胞增生李斯特菌的抽样和筛选，中国。1234份样本中有46份证实为单核细胞增生李斯特菌阳性，总阳性率为3.7%。调味生肉的污染率最高(15.2%),其次为生禽肉及生畜肉(9.9%)及三文鱼生鱼片(9.5%)。单核细胞增生李斯特菌分离株属于四种血清型，1/2a,1/2b,1/2c,4b,最普遍的血清型为1/2a（47.9％）。通过多位点序列分型（MLST）将所有分离株分为15种序列类型（ST），属于14种克隆复合物（CC）。最普遍的ST是ST9/CC9（23。9%)，其次是ST3/CC3（19.6%）和ST121/CC121（17.4%）。值得注意的是,从即食(RTE)食品中检测到11种STs，其中一些已被证实与临床起源的李斯特菌病病例密切相关，例如ST3、ST2、ST5、ST8和ST87。李斯特菌致病性岛1（LIPI-1）和LIPI-2在大约所有单核细胞增生李斯特菌分离物中检测到，而LIPI-3基因和LIPI-4基因的分布均显示出与特定ST相关，在ST3和ST288中使用LIPI-3,在ST87中使用LIPI-4。本研究中携带LIPI-3和LIPI-4毒力基因的菌株均从RTE食品中分离。药敏试验表明,>90%的菌株对PEN敏感,AMP,ERY,CIP,SXT,货车,CHL和GEN,表明抗生素治疗可能对大多数单核细胞增生李斯特菌菌株仍然有效。然而,对于三种临床一线抗生素(PEN，AMP和GEN），我们还观察到3个和4个菌株的MIC值高于PEN和AMP的敏感性标准，分别,和一株对GEN表现出抗性。
