COMBINED USE OF RIBOTYPING, PFGE TYPING AND IS431 TYPING IN THE DISCRIMINATION OF NOSOCOMIAL STRAINS OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS

We have previously reported the phenotypic characterization of methici llin-resistant Staphylococcus aureus (MRSA) clinical strains isolated in Malaya University Hospital in the period 1987 to 1989 using antibio gram, coagulase typing, plasmid profiles, and phage typing. Here, we r eport the analysis of the same strains with three genotyping methods; ribotyping, pulsed-field gel electrophoresis (PFGE) typing, and IS431 typing (a restriction enzyme fragment length polymorphism analysis usi ng an IS431 probe). Ribotyping could discriminate 46 clinical MRSA str ains into 5 ribotypes, PFGE typing into 22 types, and IS431 typing int o 15 types. Since the differences of the three genotyping patterns fro m strain to strain were quite independent from one another, the combin ed use of the three genotyping methods could discriminate 46 strains i nto 39 genotypes. Thus, the powerful discriminatory ability of the com bination was demonstrated.