Evaluation of Various Methods for Detection of Methicillin Resistance Staphylococcus aureus (MRSA)

Lee, Hye Soo; Lim, Hyun

Abstract

BACKGROUND: Traditional antimicrobial susceptibility test methods for detection of methicillin resistant Staphylococcus aureus(MRSA) require 24 hours to perform. In addition, accuracies of these methods can be influenced by prevalence of strains that express heterogeneous resistance. The mechanism of methicillin resistance in S. aureus is based on the production of an additional lowaffinity penicillin binding protein (PBP 2a), which is encoded by mecA gene. Therefore, PCR for mecA gene and immunological methods for PBP 2a could be used to determine resistance, but most clinical laboratories do not have resources to efficiently perform these technique on routine basis. Recently, slide latex agglutination test using latex particles sensitized with a monoclonal antibody against PBP 2a for the direct detection of PBP 2a was developed. In this study, we evaluated this new latex agglutination test, and compared to oxacillin disk diffusion test and PCR detection of mecA gene for detection of MRSA.
METHODS
A total 151 clinical isolates of coagulase positive S. aureus were selected. All isolates were subjected to "blinded"testing with oxacillin disk diffusion, PBP 2a latex agglutination, and mecA PCR for detection of MRSA.
RESULTS
Of 151 S. aureus, 116 (76.8%) strains were MRSA. The sensitivities and specificities of disk diffusion, latex agglutination and PCR were 94.0 and 91.4%, 97.4 and 100%, 98.3 and 100%, respectively.
CONCLUSIONS
PCR for detection of mecA gene and latex agglutination test for PBP 2a are more sensitive and specific methods for detection of MRSA than oxacillin disk diffusion test. Latex agglutination test is rapid, simple, and easier to perform than PCR. In conclusion, PBP 2a detection with latex agglutination test has the potential to be used for routine applications in the microbiology laboratory where mecA gene detection with PCR is not readily available.