Comparison of DNA sequencing of the protein A gene polymorphic region with other molecular typing techniques for typing two epidemiologically diverse collections of methicillin-resistant Staphylococcus aureus.

The aim of this study was to compare the recently developed typing approach for methicillin-resistant Staphylococcus aureus (MRSA) based on the DNA sequencing of the protein A gene polymorphic region (spaA typing) with a combination of three well-established molecular typing techniques: ClaI-mecA vicinity polymorphisms, ClaI-Tn554 insertion patterns, and SmaI pulsed-field gel electrophoresis (PFGE) profiles. In order to evaluate the applicability of this typing technique in different types of studies, two groups of MRSA clinical isolates were analyzed: a collection of 185 MRSA isolates circulating in Hungary recovered from 17 hospitals in seven cities during a 3-year period (1994 through 1996), and a selection of 53 MRSA strains isolated in a single hospital in Hungary between 1997 and 1998. The 238 MRSA clinical strains from Hungary were first classified in clonal types (defined as ClaI-mecA::ClaI-Tn554::SmaI-PFGE patterns), and 65 of the 238 strains, representing major MRSA clones and some sporadic clones, were further analyzed by spaA typing. Our results showed that the lineages most recently introduced in the hospital setting showed little variability in spaA types, whereas the MRSA clones circulating for a longer period of time and spread among several hospitals showed a higher degree of variability. The implementation of the spaA typing method was straightforward, and the results obtained were reproducible, unambiguous, and easily interpreted. This method seems to be adequate for outbreak investigations but should be complemented with other techniques in long-term surveillance or in studies comparing distant clonal lineages.