PHENOTYPIC DETECTION OF INDUCIBLE CLINDAMYCIN RESISTANCE IN STAPHYLOCOCCUS AUREUS: A STUDY FROM A TERTIARY CARE HOSPITAL IN WEST BENGAL

Introduction : The increasing prevalence of methicillin resistance among  Staphylococci  is an alarming problem. MRSA isolates with inducible clindamycin resistance (iCR) are resistant to erythromycin and sensitive to clindamycin on routine testing. D-test can help to determine whether clindamycin could be used as a therapeutic option. Hence the present study was undertaken to detect incidence of inducible resistance to clindamycin in erythromycin resistant S. aureus isolates by D test and to study the association between clindamycin and methicillin resistance. Materials and Methods : Two hundred and seven isolates of Staphylococcus aureus were tested for methicillin resistance using cefoxitin (30µg) disc by Kirby Bauer disc diffusion method. Inducible resistance to Staphylococci was tested by D test as per CLSI guidelines. Results : Of the total 207 isolates tested, 126 were erythromycin resistant. Among the erythromycin resistant isolates, 37(29.3%) showed clindamycin resistance, 47(37.3%) showed constitutive resistance and the remaining 42(33.3%) were of MS phenotype. Inducible and constitutive resistance was higher in MRSA as compared to MSSA(32.8%,44.2% and 25%,28.5%) respectively. Conclusion : The study emphasizes the fact that every microbiology laboratory should perform D test on routine basis. This will help in detecting inducible clindamycin resistance and thus prevent therapeutic failure.