APPLICATION OF GENOMIC DNA SUBTYPING BY PULSED-FIELD GEL-ELECTROPHORESIS AND RESTRICTION ENZYME ANALYSIS OF PLASMID DNA TO CHARACTERIZE METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS FROM 2 NOSOCOMIAL OUTBREAKS

Pulsed-field gel electrophoresis (PFGE) and restriction enzyme analysis of plasmid DNA (REAP) were applied to study the epidemiologic relationship among methicillin-resistant Staphylococcus aureus (MRSA) isolates from outbreaks in two hospitals in Sao Paulo, Brazil: 82 MRSA isolates, 73 from a university hospital and nine from a general adult intensive care unit of a private hospital, were collected from 62 patients: 95% of the MRSAs were also resistant to gentamicin and ciprofloxacin. REAP subtyping of both collections identified six different subtypes: 55 (72.6%) MRSAs from the university hospital and nine isolates from the private hospital shared the same epidemic REAP subtype. Discrimination by restriction of genomic DNA with Sma I followed by PFGE enabled the identification of 14 DNA subtypes. Based an the combined REAP-genomic DNA subtype, the predominant subtype in the university hospital was AIA (44 isolates) whereas the epidemic subtype in the private hospital was AIM (seven isolates). The application of two typing methods showed better discrimination among MRSAs than did either method alone.