Type II and type IV topoisomerase mutations in clinical isolates of Morganella morganii harbouring the qnrD gene

INTRODUCTION: The aim of this study was to show the emergence of the qnrD gene among fluoroquinolone-resistant Morganella morganii isolate. The occurrence of mutations in DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC,parE) genes was also investigated in this strain. METHODOLOGY: 95 clinical Enterobacteria were screened for harbouring the qnrD gene. The clinical isolate of M. morganii was recovered from urine from a patient hospitalized in the urology unit at Fattouma Bourguiba Hospital, Tunisia. Antibiotic susceptibility was tested with the agar disk diffusion method. Quinolone susceptibility was studied with microbroth dilution technique. The investigations of plasmid mediated quinolone resistance (PMQR) and topoisomerases mutations were performed by polymerase chain reaction and nucleotide sequencing. RESULTS: This isolate showed high level of resistance to quinolones. The MIC with microbroth dilution technique was 512 μg/ml for norfloxacin, 256 μg/ml for ofloxacin and ciprofloxacin and 64μg/ml for levofloxacin. This strain was found to harbour the quinolone resistance determinant qnrD. In addition, this strain harboured two new gyrB mutations (S463A, S464Y) and one parC mutation (S80I). CONCLUSIONS: This is the first report in Tunisia of qnrD determinant and tow new gyrB muations in M. morganii. The nosocomial infection due to this proteeae invites further study of its epidemiologic evolution.