AUTHOR=Li Lili , Olsen Rikke Heidemann , Xiao Jian , Liang Meidan , Meng Hecheng , Peng Shifu 

TITLE=Characterization of extended-spectrum cephalosporins and fluoroquinolone resistance of a Salmonella enterica serovar Thompson isolate from ready-to-eat pork product in China

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.964009

DOI=10.3389/fmicb.2022.964009

ISSN=1664-302X

ABSTRACT=<p><italic>Salmonella</italic> is a leading cause of foodborne illness worldwide and is a common concern in food safety. <italic>Salmonella enterica</italic> displaying resistance to extended-spectrum cephalosporins (ESCs) and fluoroquinolone (FQs) has been deemed a high-priority pathogen by the World Health Organization. Co-resistance to ESCs and FQs has been reported in <italic>S. enterica</italic> serovar Thompson (<italic>S</italic>. Thompson). However, the genetic context of ESCs and FQs resistance genes in <italic>S</italic>. Thompson lacks sufficient characterization. In this study, we characterized a multi-drug resistant (MDR) <italic>S</italic>. Thompson isolate recovered from a retail ready-to-eat (RTE) pork product in China. Short- and long-read sequencing (HiSeq and MinION) of the genome identified the presence of <italic>bla</italic><sub>CMY−2</sub>, <italic>qnrS1</italic>, and <italic>qepA8</italic>, along with 11 additional acquired antimicrobial resistance genes, residing on a 152,940 bp IncA/C plasmid. Specifically, the <italic>bla</italic><sub>CMY−2</sub>, <italic>qnrS1</italic>, and <italic>qepA8</italic> genes were located in insertion sequences (ISs) and integron mediated mobile genetic structure, <italic>sugE</italic>-<italic>blc</italic>-<italic>bla</italic><sub>CMY−2</sub>-IS<italic>Ec9</italic>, IS<italic>26</italic>-<italic>orf6</italic>-<italic>qnrS1</italic>-<italic>orf5</italic>-IS<italic>Kpn19</italic>, and <italic>intl1</italic>-<italic>qepA8</italic>-<italic>orf10</italic>-IS<italic>91</italic>-<italic>orf1</italic>-<italic>dfrA12</italic>-<italic>orf11</italic>-<italic>aadA2</italic>-<italic>qacE</italic>Δ<italic>1</italic>-<italic>sul1</italic>, respectively. Each gene was identified in various bacteria species, indicating their high transfer ability. The plasmid was found to be transferable to <italic>Escherichia coli</italic> J53 by conjugation and resulted in the acquiring of multiple resistances in the transconjugants. The plasmid is closely related to plasmids from two human <italic>S</italic>. Thompson strains isolated in different regions and years in China. Moreover, core-genome Multi Locus Sequence Typing (cgMLST) and phylogenetic analysis based on global 1,868 <italic>S</italic>. Saintpaul isolates showed that the <italic>S</italic>. Thompson isolate was highly epidemiologically linked to a human isolate in China. Our findings suggest that Chinese RTE pork products are a possible source of human pathogenic ESCs and FQs co-resistant <italic>S</italic>. Thompson. Furthermore, the results underline the important role of conjugative plasmids in acquiring and transmission of ESCs and FQs resistance in <italic>S</italic>. Thompson isolates, which need continuous investigation.</p>