Assessment of The Prevalence of Methicillin Resistant Staphylococcus aureus (MRSA) with Different Methods

The aim of this prospective study was to determine the prevalence of methicillin resistant Staphylococcus aureus that were isolated from various clinical specimens in our hospital and to search for methicillin resistance by using different methods. Hundred and seventeen isolates were studied. Of these, 41(35%) were found to be resistant to methicillin with agar dilution; 39 (33.3%) with agar screening and 38 (32.5%) with disk diffusion. Of the resistant strains, 27 (65.8%) were found to be positive both for beta-lactamase and mec A; while 3 (7.4%) only for mec A; 6 (14.6%) only for beta-lactamase. Neither beta-lactamase nor mec A were determined in 5 (12.2%) strains. As a conclusion we have found no statistically significant difference in sensitivity and specificity between agar screening and disk diffusion methods used in the detection of methicillin resistance (Mc Nemar and Cohen Kappa statistical tests were used in the study). Yet we recommend to retest the isolates which are found to be methicillin resistant by disk diffusion method used routinely, with agar screening also which is cheaper and more simple. Than dilution tests this test can give additional information about MIC levels. Furthermore exploring for mec A gene in these isolates contributes more in therapeutic approach