Trend of plasmid-mediated quinolone resistance genes at the Childrens Hospital in Tunisia.
The prevalence of plasmid-mediated quinolone resistance (PMQR) genes (qnr, aac(6) Ib-cr and qepA) was sought among Enterobacteriaceae strains obtained from the Childrens Hospital of Tunis (Tunisia). Nonduplicate isolates (n= 278) with resistance to extended-spectrum cephalosporins and collected in 2003, 2007, 2008 and 2009 were screened for qnr genes. Forty (14.4%) isolates were qnr positive and were then screened for the presence of aac(6)-Ib-cr and qepA genes. qnrB was detected in 21 Klebsiella pneumoniae, 11 Escherichia coli and in 6 Enterobacter cloacae isolates. Sequence analysis of the qnrB amplicons revealed variants including 24 qnrB1, 11 qnrB2, and 3 qnrB6. qnrS (qnrS1 allele) was detected only in K. pneumoniae isolates, either alone (two isolates) or with qnrB gene (one isolate). qnrA, qnrC and qnrD genes were not found in any of the 278 isolates. No qnr-positive isolates carried qepA gene. Pyrosequencing results showed that aac(6)-Ib-cr, a variant of aac(6)-Ib gene, was present in 31 qnr-positive isolates (21 K. pneumoniae isolates, 7 E. coli isolates, and 3 E. cloacae isolates). aac(6)-Ib was also found either alone (two isolates) or in association with aac(6)-Ib-cr (one isolate). Of the forty qnr-positive isolates, 92.5%, 82.5%, 57.5%, 85%, and 82.5% were nonsusceptible to nalidixic acid, ciprofloxacin, levofloxacin, ofloxacin, and norfloxacin, respectively, and all were ESBL producers. Random amplified polymorphic DNA-PCR typing of these isolates showed 16, 8, and 5 different genotypes in K. pneumoniae, E. coli, and E. cloacae isolates, respectively. Our study highlights the high prevalence of qnr in association with aac(6)-Ib-cr among Enterobacteriaceae isolates even from children who are patients not overtreated with quinolones.