Introduction: Methicillin resistant S. aureus (MRSA), which are often resistant to several classes of antibiotics, is the most common cause of nosocomial infections.

Aim: The objective of the study was 1)to find out antibiotic susceptibility pattern  of clinically significant  Staphylococcus aureus  isolated from various samples and, 2)to compare four methods for MRSA detection.

Materials and Methods: This is a cross sectional study conducted in the Department of Microbiology, Govt. Medical College, Thiruvananthapuram. During the study period 208 strains of Staphylococcus aureus were collected and were characterized. Antibiotic susceptibility was performed by disc diffusion test using Clinical Laboratory Standards Institute guidelines. Polymerase chain reaction was done for the detection of mec A gene. D test was performed for those strains which were resistant to Erythromycin. The present study was undertaken to compare four phenotypic methods for the detection of MRSA, namely, the Cefoxitin disc diffusion method, Oxacillin screen agar, HiChrome agar and Mannitol salt agar with Cefoxitin.

Results: Among MSSA,(152) resistance to Penicillin, Erythromycin, Ciprofloxacin, Tetracycline, Gentamicin, Clindamycin and Cotrimoxazole were 94.73%, 9.8%, 59.86%, 3.94%, 36.84%, 7.89%  and 15.78% respectively. Among MRSA,(56) resistance to Erythromycin, Ciprofloxacin, Tetracycline, Amikacin, Clindamycin and Cotrimoxazole were 57.14%, 73.21%, 67.85%, 14.28%, 28.57% and 57.14% respectively. Vancomycin E strip test was done for all MRSA isolates (56), and all of them had MIC below 2µg.(sensitive) Sensitivity of Oxacillin screen agar was 91.07% and specificity was 100%.For other methods sensitivity and specificity was 100%.

Keywords: MRSA, Erythromycin induced Clindamycin resistance, Vancomycin E test.

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L.R.Shini Raj

Lecturer, Govt. Medical College, Thiruvananthapuram