Prevalence of plasmid-mediated quinolone resistance determinants in Enterobacteriaceae from Tunisia

摘要

The spread of plasmid-mediated quinolone resistance determinants (qnr-like determinants, aac(6')-lb-cr and qepA genes) was evaluated in a collection of 281 nalidixic acid-resistant enterobacterial isolates recovered between September 2005 and December 2007 at the Sahloul Hospital, Sousse, Tunisia. Sixteen percent of those isolates carried qnr genes encoding the QnrBI, QnrB2, QnrA6 or QnrSI determinants. Most qnr-positive isolates were extended-spectrum beta-lactamase (ESBL) producers, being predominantly of the CTX-M-15 type, but also of the SHV-28 and SHV-12 types. The qnr genes were located on plasmids with a size in the range 55-150 kb. The qnrB2 gene was associated with su//-type integron structures and the qnrBI gene was associated with orfl005, whereas the genetic environment of qnrA6 was unknown. In two isolates, the qnrSl gene was located downstream of an ISEc/2 element on plasmids that often carried the narrow-spectrum beta-lactamase gene bla_LAP-2 qepA and aac(6')-lb-cr were not detected. The present study highlights the wide spread of Qnr-like determinants in Tunisia, with an association with the ESBL CTX-M-15 in human clinical isolates.