Background： Meicillin-resistant Staphylococcus aureus(MRSA) is a common cause of nosocomial infections worldwide. Identification of strains by molecular typing facilitates epidemiological studies and improves disease control. This study was performed to determine the usefulness of mecA-associated hypervariable region(HVR) polymerase chain reaction (PCR) and random amplified polymorphic DNA(RAPD) analysis in the investigation of a nosocomial MRSA infections.

Methods：Methicillin-resistance was identified by NCCLS disk diffusion method using the oxacillin disk. And PCR was done for detection of mecA gene. Antimicrobial susceptibility test, HVR-PCR and RAPD using 3 primers were performed for epidemiological analysis on isolates of MRSA.

Results：During the period from 1997 Dec. to 1998 May, 120 strains of S. aureus were isolated from clinical specimens. Among them, 78 strains were MRSA, and 72 strains were mecA positive. The strains of mecA positive MRSA were classified into four types by antibiogram, six genotypes by HVR-PCR, and 29 groups by RAPD using three primers. The combination of HVR genotypes and RAPD analysis showed 43 different types in 72 mecA positive MRSA isolates. The five strains which were repeatedly isolated from the same patients showed the same HVR genotypes and RAPD analysis.

Conclusions：Antibiogram, HVR-PCR, and RAPD could classify MRSA isolates into only 4-6 types, respectively, but combination of these methods could improve the typability. And combination of results of RAPD analysis using three primers were better than that using one primer in epidemiological studies of MRSA because of same reasons. It can be concluded that molecular typing of MRSA using HVR-PCR and RAPD assay is useful in epidemiolgical investigation of nosocomial infections caused by MRSA, because of its simplicity and reproducibility. (Korean J Clin Microbiol 1999;2:40~48)