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Objective@#To analyze the molecular characteristics of Listeria monocytogenes strains from ready-to eat food in China.@*Methods@#A total of 239 Listeria monocytogenes strains isolated from ready-to-eat food in 2017, all strains underwent whole-genome sequencing (WGS) , and comparisons uncovered population structure derived from lineages, clonal complex, serogroups, antimicrobial susceptibility and virulence, which were inferred in silico from the WGS data. Core genome multilocus sequence typing was used to subtype isolates.@*Results@#All strains were categorized into three different lineages, lineage Ⅱ was the predominant types in food, and IIa was the main serogroups. CC8, CC101 and CC87 were the first three prevalent CCs among 23 detected CCs, accounting for 49.4%. Only 4.6% (11 isolates) of tested strains harbored antibiotic resistance genes, which were mostly trimethoprim genes (7 isolates, 2.9%). All strains were positive for LIPI-1, and only a part of strains harbored LIPI-3 and LIPI-4, accounting for 13.8% (33 isolates) and 14.2% (34 isolates), respectively. ST619 carried both LIPI-3 and LIPI-4. 51.5% (123 isolates) of strains carried SSI-1, and all CC121 strains harbored SSI-2. Different lineages, serogroups and CCs can be separated obviously through cgMLST analysis, and 24 sublineages were highly concordant with CCs.@*Conclusion@#Ⅱa was the main serogroups in ready-to-eat food isolates in China; CC8, CC101 and CC87 were the prevalent CCs, and CC87 isolates was hypervirulent isolates, cgMLST method can be adopted for prospective foodborne disease surveillance and outbreaks detection.
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Objective To study the serotype distribution characteristics and genotypes of Salmo-nella strains isolated in Yunnan Province from 2015 to 2017. Methods Automatic microbiological identifi-cation system and mass spectrometer were used to identify Salmonella strains. Their serotypes were detected using the White-Kauffmann-Le Minor (WKL) scheme based on serological detection. Genotyping was car-ried out by referring to the molecular typing method of Salmonella serotype pulse field gel electrophoresis (PFGE) in PulsenetChina. Cluster analysis was performed with Bionumerics (7.6). Results A total of 408 strains of Salmonella were detected in food and patients in Yunnan Province form 2015 to 2017,belong-ing to 70 serotypes. Thirty-four Salmonella derby strains were detected in food,accounting for 19.10% of all Salmonella strains detected in food. Among the Salmonella strains detected in patients,71 were Salmonella enteritis and 67 were Salmonella typhimurium,accounting for 30.34% and 27.63%, respectively. Results of PFGE revealed that Salmonella derby and Salmonella typhimurium were polymorphic,and Salmonella en-teritis had obvious advantages PFGE band patterns. No obvious time or geographical aggregation was found in the PFGE bands of the three Salmonella species. Conclusion Seventy Salmonella serotypes had been iden-tified in Yunnan Province by 2017. Salmonella derby was the predominant serotype detected in food, while Salmonella enteritidis and Salmonella typhimurium were the predominant serotypes in patients. These three Salmonella species caused sporadic infections in Yunnan Province.