Antimicrobial and pathogenic characterization of Listeria monocytogenes isolated from ready-to-eat meats

Abstract

ObjectiveTo determine the antimicrobial susceptibilities of 33 Listeria monocytogenes cultured from ready-to-eat (RTE) meats in China and to use whole genome sequencing (WGS) to characterize the antimicrobial resistance and virulence genotypes of these isolates.MethodsThe susceptibilities of 33 Listeria monocytogenes were determined by broth microdilution. These isolates were then sequenced using short-read high accuracy protocols. The corresponding genomes were assembled and further analysis was carried out using appropriate bioinformatics pipelines.ResultsAll isolates were found to be susceptible to ampicillin, trimethoprim-sulfamethoxazole, gentamicin, meropenem and vancomycin. One isolate was resistant to tetracycline and erythromycin at the same time. All 33 L. monocytogenes were classified into 13 STs, among them ST9, ST87, ST122 were the dominant, from which resistant isolate belonged to ST87. The genotypes of the resistant isolate correlated well with its resistant phenotype. Up and down stream analysis of the genetic context, in which these resistant genes were found, suggested that they may have been acquired from Erysipelothrix rhusiopathiae and Blautia product. All isolates harboured LIPI-1 and LIPI-2, 7 of them harbored LIPI-3, and 8 harboured LIPI-4(1 ST121 and 7 ST87).ConclusionThese data showed that acquired resistance existed in this bacterium from RTE meats origins, and can be a potential public health risk due to its high harboring rate of LIPI-3 and LIPI-4. It was suggested that the monitoring of L. monocytogenes in RTE meats should be strengthened in the future, specifically for ST87.

Keywords

• listeria monocytogenes
• ready-to-eat meats
• antimicrobial susceptibility-testing
• whole genome sequencing