Phenotypic and genomic characterization of a multidrug-resistant Salmonella enterica serovar Kentucky ST198 isolated from a patient in China

Abstract

ObjectivesTo investigate the resistance mechanisms of a multidrug-resistant Salmonella Kentucky ST198 FJ-2064 isolated from a patient in China. MethodsThe antimicrobial susceptibility of FJ-2064 was determined by the standard disc dilution and broth microdilution methods. The complete genome of FJ-2064 was sequenced using PacBio and Illumina MiSeq platforms. PCR and S1-PFGE were utilised to confirm the mutation sites and the genomic plasmids, respectively. ResultsIsolate FJ-2064 belongs to sequence type ST198 and harboured no visible large plasmids, but was concurrent resistant to 22 detected antimicrobial agents including cefotaxime, ciprofloxacin and azithromycin. The complete genome sequence identified 20 acquired antibiotic resistance genes (ARGs) and five chromosomal mutations in the gyrA and parC genes of the quinolone resistance determining regions (QRDRs) in FJ-2064. In addition, PCR sequencing confirmed that most of the ARGs were clustered on one multidrug-resistant region and a variant of SGI1-K. In particular, the bla-TEM-1 and bla-CTX-M-55, qnrS1, mph(A) genes, which confer resistance to cephalosporins, quinolones, and macrolides respectively, were all located on the multidrug-resistant region. ConclusionsWe have demonstrated one multidrug-resistant region and a variant of SGI1-K in a Salmonella Kentucky ST198 that is co-resistant to cefotaxime, ciprofloxacin and azithromycin.