Resistance genes and plasmids of a multi-drug resistant Shigella sonnei strain carrying both bla_CTX-M-14 and bla_CTX-M-15 genes

  Objective  To analyze the whole genome sequencing of a multi-drug resistant Shigella sonnei strain resistant to both cephalosporin and azithromycin and identify the characteristics of its resistance genes and plasmids.

  Methods  A cephalosporin and azithromycin resistant S. sonnei strain (Sh11sh529) was screened by analyzing the antibiotic susceptibility of 60 S. sonnei strains collected from Shanghai in 2011, and genome sequence of the strain was obtained by second-generation sequencing and nanopore sequencing technology. The drug resistance genes, plasmids and genetic mobile elements were analyzed.

  Results  Eleven resistance genes and gyrA-S83L mutation sites in quinolone resistance determining region (QRDR) of gyrA gene were detected in genome of the Sh11sh529 strain. The resistance genes included two extended spectrum β-lactamases (ESBLs) genes bla_CTX-M-14 and bla_CTX-M-15. The bla_CTX-M-14, mphA, aac(3)-IId, dfrA17, aadA5, sul1 and qacEdelta genes were carried by an IncB/O/K/Z plasmid (pSh11sh529-2). There was an ISEcp1 insert in upstream of bla_CTX-M-14, an IS26 insert in upstream of mphA. The bla_CTX-M-15 gene was carried by an IncFII plasmid (pSh11sh529-3), and there was an ISEcp1 insert in upstream of bla_CTX-M-15. The strain was resistant to 9 antibiotics of 5 classes, including cephalosporins, macrolides, aminoglycosides, sulfonamides, and penicillins.

  Conclusion  It is necessary to strengthen the surveillance and research of multi-drug resistant strains and strains carrying multiple types of ESBL for the development of strategies to reduce the prevalence and spread of multi-drug resistant strains.