D-test – its role in detection of inducible resistance to clindamycin in staphylococcus aureus with special reference to mrsa.

Authors:Veena Manjunath, Eshwar Singh, Ramya.T.G, Mridula Raj Prakash, Archana Sharma
Int J Biol Med Res. 2012; 3(1): 1430-1432  |  PDF File

Abstract

Context: Staphylococcus aureus is a very widely occurring pathogen causing both nosocomial and community acquired infections globally. It is developing resistance to a wide variety of drugs tested routinely. Clindamycin which was very effective for most of the skin and soft tissue infections is also receding in its effect due to evolution of resistant strains. Aim: This study aims to know the details of different phenotypes involved in inducible resistance to clindamycin in erythromycin resistant isolates and also the association of MRSA and the inducible resistance. Materials and Methods: 96 S.aureus isolates were subjected to routine antibiotic susceptibility testing including Erythromycin, Clindamycin and Cefoxitin by Kirby Bauer disc diffusion method. Inducible clindamycin resistance was detected by disc approximation test (D test) as per CLSI guidelines. Results: Among the 96 isolates tested, 59 (61.45%)were found to be MRSA and 37(38.54%) were MSSA. Of the 59 isolates,34(57.63%)showed inducible clindamycin resistance,14(23.73%) constitutive resistance and 11(18.64%). Conclusion: High incidence of inducible and constitutive resistance was observed in MRSA as compared to MSSA. We suggest use of D test routinely to detect true resistance to clindamycin and to avoid treatment failure.