AUTHOR=Li Lili , Olsen Rikke Heidemann , Xiao Jian , Meng Hecheng , Peng Shifu , Shi Lei 

TITLE=Genetic context of blaCTX–M–55 and qnrS1 genes in a foodborne Salmonella enterica serotype Saintpaul isolate from China

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.899062

DOI=10.3389/fmicb.2022.899062

ISSN=1664-302X

ABSTRACT=<p><italic>Salmonella enterica</italic> resistant to fluoroquinolones (FQs) and extended-spectrum cephalosporins (ESCs) has been deemed a high-priority pathogen by the WHO. <italic>Salmonella enterica</italic> serovar Saintpaul (<italic>S</italic>. Saintpaul) co-resistant to ESCs and FQs and harboring corresponding resistance genes (<italic>bla</italic><sub>CTX–M–55</sub> and <italic>qnrS1</italic>) have been previously reported. However, they have not been reported in China. Moreover, the genetic context and transferability of ESCs and FQs resistance genes in <italic>S</italic>. Saintpaul remain obscure. This study is the first study to characterize a multidrug-resistant (MDR) <italic>S</italic>. Saintpaul isolate (16Sal016) harboring plasmid-mediated <italic>bla</italic><sub>CTX–M–55</sub> and <italic>qnrS1</italic> genes recovered from weever fish in China. The whole genome short- and long-read sequencing results identified the presence of 15 acquired antibiotic resistance genes encoding resistance to nine classes of antibiotics, as well as abundant mobile genetic elements residing on a 259,529 bp IncHI2 plasmid. The <italic>bla</italic><sub>CTX–M–55</sub> and <italic>qnrS1</italic> genes were located in a 12,865 bp region, IS<italic>26</italic>-<italic>orf</italic>-<italic>orf</italic>-IS<italic>Kpn19-qnrS1</italic>-IS<italic>3</italic>-Tn<italic>3</italic>-<italic>orf</italic>-<italic>bla</italic><sub>CTX–M–55</sub>-IS<italic>Ec9</italic>-<italic>orf</italic>-IS<italic>26</italic>. Similar structures have been identified in various bacterial species, indicating a high transferability of <italic>bla</italic><sub>CTX–M–55</sub> and <italic>qnrS1</italic> genes within this gene cluster. The plasmid was found to be transferable to <italic>Escherichia coli</italic> (<italic>E. coli</italic>) J53 by conjugation and resulted in the acquisition of multiple resistances by the transconjugants. Genome sequence comparisons by core genome multilocus sequence typing (cgMLST) based on global 2,947 <italic>S</italic>. Saintpaul isolates indicated that strain 16Sal016 was epidemiologically linked with an isolate from the United Kingdom (UK). Our findings suggest that plasmids and IS<italic>26</italic>-mediated mobile genetic elements are carriers of <italic>bla</italic><sub>CTX–M–55</sub> and <italic>qnrS1</italic> genes in <italic>S</italic>. Saintpaul, and highlight their potential transmission, which needs continuous investigations.</p>