Multicenter evaluation of epidemiological typing of methicillin-resistant Staphylococcus aureus strains by repetitive-element PCR analysis

Rapid and efficient epidemiologic typing systems would be useful to monitor transmission of methicillin-resistant Staphylococcus aureus (MRSA) at both local and interregional levels. To evaluate the intralaboratory performanc e and interlaboratory reproducibility of three recently developed repeat-el ement PCR (rep-PCR) methods for the typing of MRSA, 50 MRSA strains charact erized by pulsed-field gel electrophoresis (PFGE) (SmaI) analysis and epide miological data were blindly typed by inter-IS256, 16S-23S ribosomal DNA (r DNA), and MP3 PCR in 12 laboratories in eight countries using standard reag ents and protocols. Performance of typing was defined by reproducibility (R ), discriminatory power (D), and agreement with PFGE analysis. Interlaborat ory reproducibility of pattern and type classification was assessed visuall y and using gel analysis software. Each typing method shelved a different p erformance level in each center. In the center performing best with each me thod, inter-IS256 PCR typing achieved R = 100% and D = 100%; 16S-23S rDNA P CR, R = 100% and D = 82%; and MP3 PCR, R = 80% and D = 83%. Concordance bet ween rep-PCR type and PFGE type ranged by center: 70 to 90% for inter-IS256 PCR, 44 to 57% for 16S-23S rDNA PCR, and 53 to 54% for MP3 PCR analysis. I n conclusion, the performance of inter-IS256 PCR typing was similar to that of PFGE analysis in some but not all centers, whereas other rep-PCR protoc ols showed lower discrimination and intralaboratory reproducibility. None o f these assays, however, was sufficiently reproducible for interlaboratory exchange of data.