Evolution and transmission of a conjugative plasmid encoding both ciprofloxacin and ceftriaxone resistance in Salmonella

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Pages (from-to)396-403
Journal / PublicationEmerging Microbes and Infections
Issue number1
Online published21 Mar 2019
Publication statusPublished - 2019
Externally publishedYes


Ceftriaxone and ciprofloxacin are the drugs of choice in treatment of invasive Salmonella infections. This study discovered a novel type of plasmid, pSa44-CIP-CRO, which was recovered from a S. London strain isolated from meat product and comprised genetic determinants that encoded resistance to both ciprofloxacin and ceftriaxone. This plasmid could be resolved into two daughter plasmids and co-exist with such daughter plasmids in a dynamic form in Salmonella; yet it was only present as a single plasmid in Escherichia coli. One daughter plasmid, pSa44-CRO, was found to carry the blaCTX-M-130 gene, which encodes resistance to ceftriaxone, whereas the other plasmid, pSa44-CIP, carried multiple PMQR genes such as qnrB6-aac(6’)-Ib-cr, which mediated resistance to ciprofloxacin. These two daughter plasmids could be integrated into one single plasmid through ISPa40 mediated homologous recombination. Mouse infection and treatment experiments showed that carriage of plasmid, pSa44-CIP-CRO by S. typhimurium led to the impairment of treatment by ciprofloxacin or cefitiofur, a veterinary drug with similar properties as ceftriaxone. In conclusion, dissemination of such conjugative plasmids impairs current choices of treatment for life-threatening Salmonella infection and hence constitutes a serious public health threat.

Research Area(s)

  • ceftriaxone resistance, ciprofloxacin resistance, conjugative plasmid, PMQR genes, Salmonella