Pollution status, drug resistance and molecular characteristics of pathogenic bacteria in raw food vegetables in Yunnan Province

Abstract

ObjectiveTo analyze Salmonella， Listeria monocytogenes and diarrheagenic Escherichia coli in vegetables in Yunnan Province， the antibiotic susceptibilities and whole genome sequencing （WGS） were determined to characterize the antimicrobial resistance and virulence genotypes of these isolates.MethodsSalmonella， Listeria monocytogenes and diarrheagenic Escherichia coli of 180 samples of vegetables that can be eaten raw were isolated and identified by National food safety standard Food GB 4789.4—2016， GB 4789.30—2016， GB 4789.6—2016. The susceptibilities of isolates were determined by broth microdilution. The whole genome of isolates was then sequenced. The corresponding genomes were assembled and further analysis was carried out using appropriate bioinformatics pipelines.ResultsTwelve of 180 samples of vegetables that can be eaten raw had isolates of pathogenic bacteria from Lactuca sativa， cilantro and Houttuynia cordata Thunb and so on. A total of 13 isolates were detected， including 7 strains of Salmonella which contain 7 serotypes， 4 strains of multi-drug resistance （drug resistance phenotype and drug resistance genes were well correlated）， 5 strains carrying IncHI and IncF plasmids related to multi-drug resistance， 4 strains of Listeria monocytogenes which contain 1 strain of multi-drug resistance and 2 strains carrying the virulence island LIPI-3. 2 strains of enteroaggregative Escherichia coli in which 1 strain of multi-drug resistance.ConclusionMore attention should be paid to vegetables that can be eaten raw with regional characteristics， such as Houttuynia cordata Thunb. Some strains of Listeria monocytogenes can be a potential public health risk due to high harboring rate of virulence genes. It is serious that of multidrug resistance of Salmonella and diarrheagenic Escherichia coli isolated from raw vegetables.

Keywords

• raw vegetables
• salmonella
• listeria monocytogenes
• diarrheagenic escherichia coli
• antimicrobial susceptibility-testing
• whole genome sequencing