First report of molecular characterization of fluoroquinolone-resistant Mycobacterium tuberculosis isolates from a Tunisian hospital.

Fluoroquinolones are increasingly used for the treatment of infections caused by multidrug-resistant Mycobacterium tuberculosis. Our study was designed to determine the frequency of the emergence of ciprofloxacin-resistant isolates in a university hospital (Rabta University Hospital Tunis, Tunisia) and to characterize the mutations responsible for the resistance phenotype. A total of 495 clinical M. tuberculosis isolates obtained from January 2005 to July 2008 were investigated for their susceptibility to ciprofloxacin, using the standard proportion method, PCR and DNA sequencing. Four resistant isolates (0.8%) were identified. Among these, only two carried point mutations in gyrA leading to amino acid changes other than the phenotypically silent S95T substitution. No gyrB missense mutations were found in any of the clinical isolates. Although fluoroquinolone resistance is still rare in Tunisia, accurate surveillance is needed in order to control the possible emergence of resistance to fluoroquinolones, which are essential for the successful treatment of multidrug-resistant tuberculosis.