SCREENING AND CONFIRMATION OF MRSA ISOLATES AND A STUDY ON THE MIC VALUES OF VANCOMYCIN AND DAPTOMYCIN USING E-TEST STRIPS

Dr. Ruksana Ahmed

Abstract


Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial and community pathogen. The objectives of this study were to determine the prevalence of MRSA in clinical specimens and to detect the sensitivity pattern of these strains against various antibiotics used for treating patients. Strains were identified using standard procedures, and their sensitivity pattern was done on Mueller Hinton agar by Kirby Bauer disc diffusion method. Mean inhibition concentration values of vancomycin and daptomycin were determined.Among 110 isolates of S. aureus, 30(30.90%) were methicillin-resistant. The antibiogram done for 34 MRSA isolates showed that there was 100% resistance to drugs like Penicillin, Oxacillin, Ampicillin, Amoxiclav, Cefoxitin, while the resistance to others was 79.41% to Erythromycin, 64.71% to clindamycin, 52.94% to Ciprofloxacin, 41.17% to Rifampicin, 2.94% to Teicoplanin, and 0% resistance to Linezolid and Tigecycline . 70.59% of the MRSA isolates had an MIC value of between 1 and 2 mcg/ml for Vancomycin. Further, 94% isolates of MRSA showed complete susceptibility to Vancomycin with MIC values below 2mcg/ml. Therefore, Vancomycin is recommended as the first line of treatment for MRSA infections. However, indiscriminate use of Vancomycin has to be avoided as it is leading to emergence and spread of Vancomycin resistance. All the MRSA isolates in the present study are found to be susceptible to Daptomycin. Therefore, in cases of Vancomycin intermediate Staphylococcus aureus (VISA), it is recommended that Daptomycin Linezolid or Tigecycline can be used for treatment.


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