Co-transfer of plasmid-mediated blaAmpC and fluoroquinolone resistance genes in Klebsiella pneumoniae isolates causing nosocomial urinary tract infection

Abstract Background: Klebsiella pneumoniae is a pathogen that frequently causes nosocomial urinary tract infection (UTI), and the prevalence of plasmid-mediated resistance determinants among clinical isolates of K. pneumoniae leads to the appearance of resistance to antibiotics. The aim of this study was to investigate the prevalence of plasmid-mediated quinolone resistance (PMQR) genes in acquired AmpC (ac-AmpC) β‑lactamase‑producing K. pneumoniae isolates from patients with nosocomial UTI and to characterize the transmissibility of plasmids co-harbouring blaAmpC and PMQR genes.Methods: From January 2017 to June 2018, we collected 46 AmpC-producing K. pneumoniae isolates causing nosocomial UTI from a tertiary care hospital in China. β-lactamase, PMQR and virulence genes were detected by PCR and sequencing. Clonal relatedness was assessed using ERIC-PCR and multilocus sequence typing (MLST). Plasmids carrying multiple blaAmpC and PMQR genes were characterized by PCR-based replicon typing (PBRT) and S1-PFGE. Conjugation and electroporation experiments were carried out to assess resistance transfer mediated by plasmids. Overlapping PCR was used to map the genetic context of the blaAmpC genes. Results: In the studied isolates, non-susceptibility of third-generation cephalosporin and fluoroquinolone was very high (>80%). blaCMY-2, blaDHA-1, and quinolone resistance gene (qnr) were detected in 11, 41 and 33 isolates, respectively. Among the isolates, 6 strains co-harboured multiple AmpC and qnrB genes. The blaAmpC and qnrB genes from these six isolates were co-transferrable to recipients via conjugation or electroporation, with IncFIA, IncFIB and IncA/C being the dominant replicons (sizes from ~78 to 217 kb). Forty-six isolates were categorized into 25 ERIC types, and the 6 isolates harbouring multiple blaAmpC and qnrB genes belonged to ST1/STnew1. The conserved genetic structures in blaCMY-2 and blaDHA-1 were identical to those described in the pNF4656 and pSAL-1 plasmids, respectively.Conclusion: This work reports that qnrB is highly prevalent in AmpC-producing K. pneumoniae isolates and illustrates the emergence of plasmids co-harbouring multiple acquired blaAmpC and qnrB genes in K. pneumoniae causing UTI in China. We determined that the IncFIA, IncFIB and IncA/C plasmids carrying blaAmpC with qnrB resistance genes and several mobile genetic elements mediate the local prevalence in K. pneumoniae UTI. The genetic context of blaAmpC was highly conserved.