Discriminatory Powers of Molecular Methods for Mrsa Differentiation

Discriminatory powers of various molecular techniques were evaluated for typing of methicillin-resistant Staphylococcus aureus (MRSA) isolated in Siriraj Hospital, Bangkok, Thailand. Thirty MRSA isolates were randomly selected in this study. They were characterized by pulsed-field gel electrophoresis, ClaI-mecA and ClaI-Tn554 polymorphisms, ribotyping, and PCR-based methods including SCCmec typing, spa and coa gene polymorphism, and repeat units in hypervariable region downstream of mecA. Individual molecular typing technique distinguished those MRSA isolates into 2 to 5 types. Eleven genetic backgrounds of MRSA isolates were elucidated by combination of typing methods with trimethoprim/sulfamethoxazole (TMP/SXT) susceptibility. Combination of all typing methods including TMP/SXT susceptibility yielded a discriminatory index of 0.94. Combination of PCR-based methods and TMP/SXT susceptibility, with the discriminatory index of 0.89, is a practical typing approach suitable for rapid epidemiological investigation of MRSA isolates in a hospital setting. SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH 328 Vol 37 No. 2 March 2006 the discriminatory powers of PFGE, Southern blot hybridization and PCR-based methods for differentiation of MRSA in a 2,400-bed university hospital in Bangkok, Thailand based on calculation of Simpson’s discriminatory index (Hunter and Gaston, 1998). MATERIALS AND METHODS