CONCORDANT CLONAL DELINEATION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS BY MACRORESTRICTION ANALYSIS AND POLYMERASE CHAIN-REACTION GENOME FINGERPRINTING

Pulsed-field gel electrophoresis of DNA macrorestriction fragments (ma crorestriction analysis) allows epidemiologic typing and delineation o f genetic relatedness of methicillin-resistant Staphylococcus aureus ( MRSA) by indexing variations in the global chromosome architecture. Po lymerase chain reaction (PCR)-mediated genome fingerprinting can also discriminate MRSA strains by detecting locally variable DNA motifs. To assess the correlation between these methods, 48 epidemic MRSA strain s collected from 20 hospitals over a 10-year period were tested in a b lind comparison by (i) macrorestriction analysis with SstII or SmaI en donuclease and (ii) PCR fingerprinting with four primer sets aimed at the mecA gene, enterobacterial repetitive intergenic consensus sequenc es, and arbitrary sequences. Isolates were discriminated into 22 macro restriction patterns and 15 PCR fingerprints. MRSA strains belonging t o 12 distinct clones by macrorestriction analysis showed 11 distinct P CR genotypes distinguished by multiple band differences. In contrast, 34 of 37 MRSA strains found to be clonally related by macrorestriction analysis clustered in two highly related PCR genotypes that differed by a single DNA fragment (P < 0.0001). These data demonstrate concorda nt clonal delineation of epidemic MRSA by macrorestriction analysis an d PCR fingerprinting and thereby indicate that the rapid PCR assay may be an efficient epidemiologic typing system.