[DNA polymorphisms in strains of Staphylococcus aureus. I. Usefulness of coagulase gene as an epidemiological marker].

In this study, we report the genotyping of Staphylococcus aureus by restriction enzyme digestion of the nested PCR products of coagulase gene from clinical strains of 83 MRSA (methicillin-resistant S. aureus) and 23 MSSA (methicillin-sensitive S. aureus). Using Alu I restriction enzyme, a total of 106 strains could be classified into 19 different restriction patterns, arbitrarily designated the genotypes 1 to 19 for strains. The DNA patterns of the PCR coagulase gene products were visualized by ethidium bromide after 2% agarose gel electrophoresis and hybridized with alkaline-phosphatase labeled probe. Because of unique sequences of the coagulase gene containing 81-bp tandem repeats and Alu I recognition sites, most of clinical strains had bands in multiples of 81 bp which allowed easy discrimination among isolates. The deduced DNA fragment sizes ranged from approximately 80 to 900 bp, and the numbers of DNA fragments generated were 2 to 9. Eighteen of the 20 MRSA strains taken from the patients hospitalized in 1991 belonged to the genotypes 2 and 3, and 27 of the 29 MRSA strains taken from patients in 1992 belonged to the genotypes 1, 2 and 3, suggesting the possibility of nosocomial outbreaks caused by these strains. In conclusion, this coagulase gene restriction fragment length polymorphism (RFLP) technique will be useful for epidemiological evaluations of nosocomial MRSA infections.