Emergence of Staphylococcus aureus strains resistant to pristinamycin in Sfax (Tunisia).

Aim: We report the emergence of Staphylococcus aureus resistant to pristinamycin in Tunisia, and the characterization of the mechanisms of resistance to macrolides and streptogramins.

Methods And Results: Five strains of S. aureus resistant to pristinamycin were recovered from the department of dermatology in a Tunisian university hospital from skin samples after oral use of pristinamycin between 2004 and 2007. Susceptibility testing showed that all isolates were resistant to quinupristin-dalfopristin (MIC=4-32mg/L), lincomycin, gentamicin, kanamycin, tobramycin, tetracycline and rifampin. One isolate was susceptible to erythromycin. All five strains were closely related after analysis by pulsed-field gel electrophoresis. erm(C) was amplified from three strains and erm(A) from one strain. vga and vat genes were amplified from all strains. None of the isolates carried the vgb gene. The vga and vat genes were typed as vga(B) and vat(B) by restriction profiles analysis after electrophoresis.

Conclusion: This is the first report of clonal emergence of S. aureus resistant to pristinamycin carrying vga and vat genes in Tunisia. The role of selective pressure of pristinamycin use is certainly the main explanation of this emergence. So we must reduce the utilisation of this antibiotic for the treatment of cutaneous and bone infectious disease caused by multidrug resistant bacteria.