COMPARISON OF IN-VITRO EFFICACY OF VANCOMYCIN, LINEZOLID AND DAPTOMYCIN AGAINST METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS

Abstract

Objective: To compare the in-vitro efficacy of vancomycin, linezolid and daptomycin against Methicillin Resistant Staphylococcus Aureus (MRSA).

Study Design: Cross sectional study.

Place and Duration of Study: Department of Microbiology, Army Medical College Rawalpindi, from Jan 2012 to Jul 2012.

Methodology: Staphylococcus Aureus isolated from routine clinical specimens were subjected to Modified Kirby Bauer disc diffusion method for detection of MRSA as per Clinical and Laboratory Standards Institute guidelines. Minimum Inhibitory Concentration (MIC) of vancomycin, linezolid and daptomycin for each of 50 non-duplicate isolates of MRSA was determined by Etest, as per manufecturer’s instructions (AB Biodisk, Solna, Sweden). The minimum concentration of the three antimicrobials required to inhibit fifty percent (MIC50) and ninety percent (MIC90) of the isolates were calculated by cumulative percentage.

Results: The Etest results revealed MIC90 of vancomycin, linezolid and daptomycin as 2μg/ml, 1μg/ml, and 0.5μg/ml respectively. Daptomycin was found to have better in vitro efficacy based upon its lowest MIC90 value.

Conclusion: Compared to vancomycin and linezolid, daptomycin has a better in vitro efficacy against MRSA. However adoption of proper antiseptic measures and a judicious use of antimicrobial agents were the strongest weapons that we can develop against the multi-drug resistant organisms like MRSA.