METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS ISOLATES RECOVERED FROM ANEW-YORK-CITY HOSPITAL - ANALYSIS BY MOLECULAR FINGERPRINTING TECHNIQUES

Fifty-five methicillin-resistant Staphylococcus aureus (MRSA) isolates collected at New York Hospital Medical Center of Queens in 1989 were analyzed by molecular fingerprinting techniques. Close to 70% of these isolates (38 of 55) shared a common pulsed-field gel electrophoretic pattern, carried the same mecA gene polymorph type II, were free of th e transposon Tn554, and would not react with a mecI-specific gene prob e. An additional five isolates shared all properties of the major MRSA clone except that they carried mecA gene polymorph type III. All thes e isolates had an extremely heterogeneous methicillin resistance pheno type that belonged to population analysis profile class 1 or 2, The re st of the 12 MRSA isolates showed a variety of chromosomal pulsed-fiel d gel electrophoretic patterns that carried different mecA polymorphs and that also gave positive reactions with DNA probes for Tn554 and fo r the mecI gene. The molecular features of the majority MRSA clone sug gest that it is an archaic MRSA isolate similar in features to early M RSA isolates recovered in the 1960s.