title: qnrA6 genetic environment and quinolone resistance conferred on Proteus mirabilis.
abstract: OBJECTIVE
  To determine the genetic location and environment of the qnrA6 gene in Proteus mirabilis PS16 where it was first described and to characterize the quinolone resistance qnrA6 confers.
  
  
  METHODS
  Transformation experiments and Southern blotting were performed for plasmid and genomic DNA of P. mirabilis PS16 to determine the qnrA6 location. Combinatorial PCRs with primers in qnrA6 and genes usually surrounding qnrA genes were used to determine the genetic environment. The qnrA6 coding region, including or not the promoter region, was cloned into vectors pTOPO and pBR322 and the MICs of six quinolones were measured for transformants of Escherichia coli TOP10 and P. mirabilis ATCC 29906 Rif(R).
  
  
  RESULTS
  qnrA6 was shown to be chromosomally encoded in P. mirabilis PS16 and its genetic environment was 81%-87% similar to that of qnrA2 in the Shewanella algae chromosome. The 5138 bp region up- and downstream of qnrA6 contained an IS10 sequence surrounded by two ISCR1. This resulted in qnrA6 being displaced 1.9 kb from its native promoter but supplied a promoter present in ISCR1. qnrA6 cloned into pTOPO and pBR322 conferred a 4-32-fold increase in fluoroquinolone MICs when expressed in E. coli but only 2-3-fold in P. mirabilis. When including the promoter region, a further increase in resistance was observed in both species, reaching MIC values above clinical breakpoints for only P. mirabilis.
  
  
  CONCLUSIONS
  qnrA6 is the first chromosomally located qnrA gene described in Enterobacteriaceae. The quinolone resistance conferred by qnrA6 depends on the proximity of an efficient promoter and the host strain where it is expressed.
authors.affiliation: Univ. Paris Diderot, Sorbonne Paris Cité, Inserm IAME, UMR 1137, F-75018 Paris, France AP-HP, Lariboisière-Fernand Widal, Bacteriology, F-75010 Paris, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Jayol
authors.affiliation: Univ. Paris Diderot, Sorbonne Paris Cité, Inserm IAME, UMR 1137, F-75018 Paris, France Military Hospital Sainte Anne, Microbiology, Toulon, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Janvier
authors.affiliation: Univ. Paris Diderot, Sorbonne Paris Cité, Inserm IAME, UMR 1137, F-75018 Paris, France Robert Debré Teaching Hospital, Bacteriology, F-51092 Reims, France Reims Medical School, EA4687 ERA, SFR CAP Santé, Reims Champagne-Ardennes University, F-51092 Reims, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Guillard
authors.affiliation: Univ. Paris Diderot, Sorbonne Paris Cité, Inserm IAME, UMR 1137, F-75018 Paris, France.
authors.forename: Françoise
authors.initials: F
authors.lastname: Chau
authors.affiliation: Military Hospital Bégin, Microbiology, St Mandé, France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Mérens
authors.affiliation: AP-HP, Pitié-Salpêtrière Hospital, Bacteriologie-Hygiène, F-75013 Paris, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Robert
authors.affiliation: Univ. Paris Diderot, Sorbonne Paris Cité, Inserm IAME, UMR 1137, F-75018 Paris, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Fantin
authors.affiliation: Univ. Paris Diderot, Sorbonne Paris Cité, Inserm IAME, UMR 1137, F-75018 Paris, France AP-HP, Lariboisière-Fernand Widal, Bacteriology, F-75010 Paris, France.
authors.forename: Béatrice
authors.initials: B
authors.lastname: Berçot
authors.affiliation: Univ. Paris Diderot, Sorbonne Paris Cité, Inserm IAME, UMR 1137, F-75018 Paris, France AP-HP, Lariboisière-Fernand Widal, Bacteriology, F-75010 Paris, France emmanuelle.cambau@aphp.fr.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Cambau
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002876:Chromosomes, Bacterial / Q000235:genetics; D003001:Cloning, Molecular; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011513:Proteus mirabilis / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D015363:Quinolones / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015363:Quinolones