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Abstract
Objectives: The aim of this study was to investigate the prevalence and the emergence of plasmid-mediated quinolone resistance among broad-spectrum beta-lactam-resistant Proteus mirabilis and Morganella morganii clinical isolates recovered in the Military Hospital in Tunisia. Methods: Of 200 strains examined, 50 exhibited resistance to quinolones. Quinolone resistance determinants (qnr and aac(6′)-Ib-cr) were characterized by multiplex PCR and sequencing. Chromosomal quinolone resistance mutations in the quinolone resistance-determining region (QRDR) and class 1 integron characterization were analysed by PCR and sequencing. The clonal relationship between the isolates was studied by pulsed-field gel electrophoresis (PFGE). Results: Fourteen isolates harboured qnrA6 and among them 8 (57%) were extended-spectrum beta-lactamase (ESBL) producers, whilst 12 (85%) isolates harboured blaDHA-1. Mutations in the QRDR were detected in gyrA (Ser83Ile, Glu87Lys), gyrB (Ser464Phe), and parC (Ser80Ile). qnrA6 and blaDHA-1 genes were found embedded in complex sul1-type class 1 integrons. A gene cassette carrying aac(6′)-Ib-cr was found located in the class 1 integron upstream of the qacEΔ1 gene. According to the PFGE analysis, the isolates were clonally unrelated. Conclusions: This is the first description in North Africa of class 1 integrons carrying blaDHA-1, qnrA6 gene, and aac(6′)-Ib-cr determinants in clinical strains of Proteus mirabilis and Morganella morganii.
Acknowledgements
This study was financially supported by the Ministry of Higher Education and Scientific Research of Tunisia. This work was also supported by a grant to M.P. and G.A. from MURST ex 60% (Ministero dell’Istruzione, dell’Università e della Ricerca).
Declaration of interest: No conflict of interest to declare.