[Prevalence of inducible clindamycin resistance in Staphylococcus aureus strains isolated from clinical samples]

Empirical treatment options for staphylococcal infections have become limited, as the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains have increased. Clindamycin has been a useful option for treating skin and soft-tissue infections caused by MRSA. However, expression of inducible macrolide-lincosamide-streptogramin B resistance (MLS(B)i) to clindamycin could limit the effectiveness of this drug. The purpose of this study was to investigate the prevalence of inducible clindamycin resistance (MLS(B)i) in S. aureus strains isolated from clinical samples (wound, abscess, blood, sterile body fluids, upper respiratory tract samples, catheter). We prospectively collected sequential non-duplicated S. aureus isolates exhibiting erythromycin resistance and clindamycin susceptibility, as determined by disk diffusion method from September 2005 to August 2007 in Baskent University Adana Research and Practice Center. Testing for MLS(B)i was accomplished by the disk-diffusion induction test (D test). A total of 892 S. aureus isolates were collected during the study period. Of these, 226 were detected as erythromycin resistant-clindamycin susceptible by disk diffusion method. The prevalence of inducible clindamycin resistance in all S. aureus isolates and erythromycin resistant-clindamycin susceptible isolates were found as 19.4% (173/892) and 76.5% (173/226), respectively. Accurate susceptibility data are important for appropriate clindamycin therapy. Since inducible clindamycin resistance is not detected by standard susceptibility tests, application of D-test on a routine basis will be helpful to detect this resistance and to help effective use of clindamycin in staphylococcal infections.