[Investigation of the new QNR-based mechanism of quinolone resistance among enterobacterial strains isolated in Henri-Mondor hospital 2002-2005].

AIM OF THE STUDY: To assess the prevalence of the novel plasmid-mediated resistance to quinolones in enterobacteria isolated in our hospital.

MATERIALS AND

METHODS

We have screened 737 enterobacterial strains isolated in Henri-Mondor hospital between 2002 and 2005 for the presence of the qnr gene by PCR using specific primers. Among them, 282 had a phenotype in concordance with extended spectrum betalactamase (ESBL). Qnr-positive strains were phenotypically and genetically characterized, and epidemiological link between the cases was investigated.

RESULTS

Five qnr+ strains were described. The global prevalence was 0.7% but 5/282 among ESBL producing strains and 0/437 among quinolone-resistant enterobacteria non producing ESBL. The sequences of the PCR products were identical to qnrA in the environment of the integron In36. All the strains harboured also the ESBL SHV-12 gene. Transfer of qnr by conjugation raised quinolone MICs from 2 to 24 times. However clinical strains harboured a higher level of quinolone resistance and harboured also DNA gyrase and topoisomerase IV mutations. Two strains were epidemiologically related by molecular typing and contact tracing revealed that the patients have been previously hospitalized in the same tertiary care center.

CONCLUSION

We described the first investigation of qnr-positive strains in one hospital in France over 4 years. Although the qnr gene prevalence is low, nosocomial transmission is already shown and the transfer of the qnr containing integron among ESBL producing strains may predict future epidemic. Surveillance will be necessary to confirm this low prevalence rate of qnr in France.