Molecular epidemiology of Listeria monocytogenes isolated from ready-to-eat food in 2017 in China / 中华预防医学杂志

To analyze the molecular characteristics of strains from ready-to eat food in China. A total of 239 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. 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. 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.

Serotyping and PFGE Type of Salmonella Isolates in Yunnan Province / 昆明医科大学学报

Objective To study the serotypes and molecular characteristics of foodborne Salmonella in Yunnan Province using pulsed field gel electrophoresis (PFGE) and to establish PFGE fingerprint database. Methods This study was carried out on the basis of the Serological typing of 322 strains of foodborne Salmonella which was isolated from Yunnan national foodborne disease surveillance from 2013 to 2016. The clustering analysis was conducted on 148 strains of Salmonella DNA restriction enzyme map by using the software of BioNumerics. Fingerprint database was established through the comparison of clustering analysis correlation on bacterial strain. Results The serotype of 322 strains of Salmonella mainly included A, B, C, D, E, F, G and other 7 groups,among which Salmonella typhimurium was the major type, accounting for 11.4% (37/322) . Cluster analysis was applied using BioNumerics software in 148 strains of Salmonella DNA restriction enzyme map. According to the different number and the different positions, electrophoresis strips were divided into 102 different PFGE patterns (Figure 1) , which was categorized into 39 clusters if 90% of the strips was similar. Conclusion Foodborne salmonella molecular classification is complex. Salmonella typhimurium is the major type. PFGE belt type presents diversity.