First Report of a Foodborne Serovar Gloucester (4:i:l,w) ST34 Strain Harboring and Genes Located in IS-Mediated Composite Transposon.

Extended-spectrum β-lactamases (ESBLs) production and (fluoro)quinolone (FQ) resistance among pose a public health threat. The objective of this study was the phenotypic and genotypic characterization of an ESBL-producing and nalidixic acid-resistant serovar Gloucester isolate (serotype 4:i:l,w) of sequence type 34 (ST34) from ready-to-eat (RTE) meat products in China. Whole-genome short and long read sequencing (HiSeq and MinION) results showed that it contained , , and genes, with and located in chromosomal IS-mediated composite transposon (IS--IS-Tn-- -IS-IS). The same genetic structure was found in the chromosome of subsp. serovar Typhimurium strain and in several plasmids of , indicating that the IS-mediated composite transposon in the chromosome of Gloucester may originate from plasmids of and possess the ability to disseminate to and other bacterial species. Besides, the structural unit -IS-Tn-- was also observed to be linked with IS in both the chromosomes and plasmids of various bacteria species, highlighting the contribution of the insertion sequences (IS and IS) to the co-dissemination of and . To our knowledge, this is the first description of chromosomal and in Gloucester from RTE meat products. Our work expands the host range and provides additional evidence of the co-transfer of and among different species of through the food chain.