Detection of inducible clidamycin resistance in Staphylococcus aureus and Staphylococcus epidermidis by using D-test

Abstract

Objectives: Clindamycin is frequently used for treatment of staphylococcal infections, particulary in skin and soft tissue infections. Resistance to this antibiotic may be constitutive or inducible. Although constitutive resistance to clidamycin can be detectd by standard susceptibility testing methods, inducible clindamycin resistance is not detected by standard broth- or agar based susceptibility test methods. This type of resistance can be detected by a simple double disc diffusion test. The aim of this study was to determine the prevalence of inducible clindamycin resistance in Staphylococcus aureus and Staphylococcus epidermidis. Methods: For detection of inducible clindamycin resistance and to estimate the rate of resistance, 100 clinical isolates of each Staphylococcus aureus and Staphylococcus epidermidis were tested with disc diffusion method by using of erythromycin (15?g) and clindamycin (2?g) discs according to CLSI (Clinical and Laboratory Standards Institute) guidline. Results: Five isolates of Staphylococcus aureus revealed inducible resistance and recorded as D phenotype and one isolate was D+, while only one isolate of Staphylococcus epidermidis was detected as D phenotype. Conclusion: Our results revealed that inducible clindamycin resistance in Staphylococcus aureus (%6) is higher than Staphylococcus epidermidis (%1). Since isolates with inducible resistance may mutate and change to constitutive resistance, can lead to treatment failure. Therefore it is necessary to examine the inducible resistance in Staphylococcus aureus strains which are resistant to erythromycin and sensitive to clindamycin.