Plasmid-mediated quinolone resistance in Australia

Microb Drug Resist. Summer 2006;12(2):99-102. doi: 10.1089/mdr.2006.12.99.


The aim of this study was to search for plasmid-encoded quinolone resistance determinants QnrA and QnrS in fluoroquinolone-resistant and extended-spectrum beta-lactamase (ESBL)-producing enterobacterial isolates recovered in Sydney, Australia, in 2002. Twenty-three fluoroquinolone-resistant, of which 16 were also ESBL-positive, enterobacterial and nonrelated isolates were studied. PCR with primers specific for qnrA and qnrS genes and primers specific for a series of ESBL genes were used. A qnrA gene was identified in two ESBL-positive isolates, whereas no qnrS-positive strain was found. The QnrA1 determinant was identified in an Enterobacter cloacae isolate and in a carbapenem-resistant Klebsiella pneumoniae isolate, both of which expressed the same ESBL SHV- 12. Whereas no plasmid was identified in the E. cloacae isolate, K. pneumoniae K149 possessed two conjugative plasmids, one that harbored the qnrA and bla (SHV)-12 genes whereas the other expressed the carbapenemase gene bla (IMP-4). The qnrA gene, was located in both cases downstream of the orf513 recombinase gene and upstream of the qnrA1 gene, a structure identical to that found in sul1-type integron In36 and qnrA-positive strains from Shanghai, China. However, the gene cassettes of the sul1-type integrons were different. This study identified the first plasmid-mediated quinolone resistance determinant in Enterobacteriaceae in Australia.

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Australia / epidemiology
  • Drug Resistance, Bacterial / genetics*
  • Enterobacter cloacae / enzymology
  • Enterobacter cloacae / genetics
  • Enterobacter cloacae / isolation & purification
  • Escherichia coli / enzymology
  • Escherichia coli / genetics
  • Escherichia coli / isolation & purification
  • Fluoroquinolones / pharmacology*
  • Genes, Bacterial*
  • Humans
  • Klebsiella pneumoniae / enzymology
  • Klebsiella pneumoniae / genetics
  • Klebsiella pneumoniae / isolation & purification
  • Plasmids*
  • Polymerase Chain Reaction
  • R Factors
  • beta-Lactamases / biosynthesis


  • Anti-Bacterial Agents
  • Fluoroquinolones
  • beta-Lactamases