Application of Infrequent-Restriction-Site Polymerase Reaction (IRS-PCR) to the Molecular Epidemiologic Analysis of Methicillin Resistant Staphylococcus aureus (MRSA)

ABSTRACT

BACKGROUND: We investigated the usefulness of infrequent-restriction-site polymerase chain reaction (IRS-PCR) compared with pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) on the molecular epidemiologic analysis of methicillin-resistant Staphylococcus aureus (MRSA). MATERIALS AND METHODS: We used fifty clinical isolates of MRSA collected from 10 university hospitals located in Seoul. We performed three procedures on these isolates PFGE using SmaI, IRS-PCR using XbaI-Hha I or EagI-Hha I, and MLST using seven house-keeping genes. We determined the clusters of molecular types by dendrogram using the unweighted pair group method with arithmetic mean (UPGMA) and Dice coefficients. RESULTS: MLST analysis showed that isolates exhibited ST1, ST5, ST72, ST89, and ST239. In PFGE, the isolates clustered into 5 major groups with 80% similarity, which subsequently became classified into 18 subgroups with 95% similarity. In IRS-PCR using EagI-HhaI restriction enzymes, there was little resolution among the patterns of isolates. However, XbaI-HhaI IRS-PCR showed 5 groups with a 90% similarity. These groups were then classified into 9 subgroups with a 95% similarity. There were no significant differences among the isolates from different hospitals. CONCLUSIONS: The XbaI-HhaI IRS-PCR method could be a useful tool in the molecular epidemiology of MRSA. Its resolution power was good enough to analyze isolates, because the patterns of IRS-PCR were closely correlated with those of MLST and showed diverse groups.