Comparison of Different Laboratory Methods for Detection of Methicillin Resistant Staphylococcus Aureus

Objective: The aim of this study was to compare four different laboratory methods for detection of methicillin resistant Staphylococcus aureus (MRSA). Design: The clinical specimens including urine, blood, wound and tracheal tube aspirates were processed for isolation of S .aureus. Setting: The samples were obtained from patients admitted in Milad hospital in Tehran,Iran. Subjects: 95 strains of S.aureus were tested with four different methods i.e. disk diffusion, oxacillin screen agar E-test and latex agglutination for methicillin resistantance. Results: Of 95 tested S.aureus; E-test revealed that 51 isolates were MRSA. Oxacillin screen agar showed two false positive MRSA. The sensitivity and specificity of oxacillin screen agar method was 96% and 95% respectively. The MRSA –Screen latex agglutination showed 54(three false positive) MRSA. The sensitivity and specificity for this method was 94% and 93% respectively. Results of susceptibility testing by disk diffusion methods in comparison with other methods were conflicting. Conclusions: Oxacillin screen agar test is a reliable alternative for detection of MRSA in clinical laboratory where MIC detection or molecular methods are not available.Also MRSA latex agglutination kit offers an interesting new approach to early detection. of MRSA.