A Study to Comparison of MIC of Linezolid on MRSA by Micro Broth Dilution and E Strip Method in Teaching Hospital, Karnataka

Although for severe MRSA infections, vancomycin is described as the first-line intravenous drug, vancomycin-resistant and intermediate isolates of Staphylococcus aureus (VRSA & VISA) have been increasingly reported throughout the world. The therapeutic and life-saving option for VRSA and VISA infections is linezolid. Objective of our study was to assess Minimum inhibitory concentration of linezolid on MRSA by micro broth dilution and E strip method. One hundred fifty isolates from clinical samples were processed. Colonies suggestive of Staphylococcus aureus were identified as MRSA using Cefoxitin (30µg) discasper Clinical and Laboratory Standards Institute (CLSI) guidelines. MRSA Positive isolates were tested for Minimum inhibitory concentration of linezolid by E Strip and Micro broth dilution method. In our study out of 150 isolates of Staphylococcus aureus, 65(43.3%) were MRSA and 85(56.7%) were MSSA. A total of 65 MRSA isolates were tested for MIC by Estrip and Micro broth dilution, which showed 100% sensitivity for linezolid. In the present study, did not come across any resistant strain. In the study total of 65 isolates were tested, According to MIC of linezolid by E Strip which majority (36.9%) had MIC <2μg/ml followed by 30.8% with MIC<1μg/ml, 23% with MIC <4μg/ml and 9.2% with MIC <0.5μg/ml. In comparison to our study approximately similar MIC values were noted in the study conducted by Stefan Riedel et al., showing 65.1% with MIC <1μg/ml, 27.9% with MIC <2μg/ml, 4.7% with MIC <0.5μg/ml and 2.3% with MIC <4μg/ml.According to MIC of linezolid by micro broth dilution majority 63.1% of the isolates were having MIC <1μg/ml, followed by 26.1% with MIC <2μg/ml, 6.1% with MIC <4μg/ml and 4.7% with MIC <0.5μg/ml.