In vivo transmission of a plasmid coharbouring bla and qnrB genes between Escherichia coli and Serratia marcescens

FEMS Microbiol Lett. 2010 Jul 1;308(1):24-8. doi: 10.1111/j.1574-6968.2010.01980.x. Epub 2010 Apr 8.


We report a Serratia marcescens and an Escherichia coli isolate simultaneously detected in the same patient. Both isolates showed susceptibility patterns suggestive of harbouring a plasmid-mediated AmpC beta-lactamase (pACBL) and a plasmid-encoded quinolone resistance (PMQR). PCR-based replicon, MOB typing, plasmid profile and Southern hybridization analyses revealed that both isolates coharboured bla(DHA-1) and qnrB genes on the same IncL/M-MOB(P13) plasmid approximately 70 kb in size. Together with the fact that both plasmids were conjugative in the laboratory, these results strongly suggest that a horizontal transfer event could take place in vivo. This is the first report of an isolate of S. marcescens harbouring a pACBL. The only phenotypic method that suggests the presence of a pACBL in an isolate harbouring an inducible chromosomal AmpC enzyme is the observation of scattered colonies near the edge of the inhibition zones of some beta-lactams. The presence of both resistance genes on the same plasmid and the reported increase in PMQR could perhaps explain the widespread distribution of bla(DHA-1) genes.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Blotting, Southern
  • Conjugation, Genetic*
  • DNA, Bacterial / genetics
  • Drug Resistance, Bacterial*
  • Escherichia coli / genetics*
  • Escherichia coli / isolation & purification
  • Escherichia coli Infections / microbiology
  • Gene Transfer, Horizontal*
  • Genes, Bacterial*
  • Genotype
  • Humans
  • Plasmids*
  • Polymerase Chain Reaction
  • Quinolones / pharmacology
  • Serratia Infections / microbiology
  • Serratia marcescens / genetics*
  • Serratia marcescens / isolation & purification
  • beta-Lactamases / genetics
  • beta-Lactams / pharmacology


  • DNA, Bacterial
  • Quinolones
  • beta-Lactams
  • beta-Lactamases