AUTHOR=Li Lili , Olsen Rikke Heidemann , Song Anhua , Xiao Jian , Wang Chong , Meng Hecheng , Shi Lei 

TITLE=First Report of a Foodborne Salmonella enterica Serovar Gloucester (4:i:l,w) ST34 Strain Harboring blaCTX–M–55 and qnrS Genes Located in IS26-Mediated Composite Transposon

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.646101

DOI=10.3389/fmicb.2021.646101

ISSN=1664-302X

ABSTRACT=<p>Extended-spectrum β-lactamases (ESBLs) production and (fluoro)quinolone (FQ) resistance among <italic>Salmonella</italic> pose a public health threat. The objective of this study was the phenotypic and genotypic characterization of an ESBL-producing and nalidixic acid-resistant <italic>Salmonella enterica</italic> 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 <italic>bla</italic><sub>CTX–M–</sub><sub>55</sub>, <italic>qnrS1</italic>, and <italic>tetB</italic> genes, with <italic>bla</italic><sub>CTX–M–</sub><sub>55</sub> and <italic>qnrS1</italic> located in chromosomal IS<italic>26</italic>-mediated composite transposon (IS<italic>26</italic>–<italic>qnrS1</italic>–IS<italic>3</italic>–Tn<italic>3</italic>–<italic>orf</italic>–<italic>bla</italic><sub>CTX–M–</sub><sub>55</sub>–IS<italic>Ecp1</italic>–IS<italic>26</italic>). The same genetic structure was found in the chromosome of <italic>S. enterica</italic> subsp. <italic>enterica</italic> serovar Typhimurium strain and in several plasmids of <italic>Escherichia coli</italic>, indicating that the IS<italic>26</italic>-mediated composite transposon in the chromosome of <italic>S.</italic> Gloucester may originate from plasmids of <italic>E. coli</italic> and possess the ability to disseminate to <italic>Salmonella</italic> and other bacterial species. Besides, the structural unit <italic>qnrS1</italic>–IS<italic>3</italic>–Tn<italic>3</italic>–<italic>orf</italic>–<italic>bla</italic><sub>CTX–M–</sub><sub>55</sub> was also observed to be linked with IS<italic>Kpn19</italic> in both the chromosomes and plasmids of various bacteria species, highlighting the contribution of the insertion sequences (IS<italic>26</italic> and IS<italic>Kpn19</italic>) to the co-dissemination of <italic>bla</italic><sub>CTX–M–</sub><sub>55</sub> and <italic>qnrS1</italic>. To our knowledge, this is the first description of chromosomal <italic>bla</italic><sub>CTX–M–</sub><sub>55</sub> and <italic>qnrS</italic> in <italic>S.</italic> Gloucester from RTE meat products. Our work expands the host range and provides additional evidence of the co-transfer of <italic>bla</italic><sub>CTX–M–</sub><sub>55</sub> and <italic>qnrS1</italic> among different species of <italic>Salmonella</italic> through the food chain.</p>