The RM test for determining methicillin-resistant Staphylococcus aureus lineages.

Staphylococcus aureus lineages evolve independently and differ in hundreds of genes. Identification of lineages can be useful for epidemiological typing and infection control at the local or global level, and can also be useful when investigating differences in pathogenesis between strains. MLST (multilocus sequence typing) and spa typing (polymorphisms in the protein A gene) are useful methods for identifying lineages but can be time-consuming and expensive. Here, we describe a method for identifying lineages using PCR, which is very easy to perform and can generate results within hours. It can also be adapted to commercial or real-time platforms. The RM (restriction modification) test is based on unique sequences found in each lineage that determine the specificity of an RM system, which detects and digests foreign DNA, thereby controlling the independent evolution of the lineages; thus, it is the ideal single gene to target for a rapid lineage test.