Evaluation of interhospital spread of methicillin-resistant Staphylococcus aureus in Sao Paulo, Brazil, using pulsed-field gel electrophoresis of chromosomal DNA.

To evaluate the interhospital spread of methicillin-resistant Staphylococcus aureus (MRSA) clone in Sao Paulo, we analyzed the restriction fragment length polymorphisms (RFLP) of chromosomal DNA from isolates from nine Sao Paulo hospitals. Restriction digestion of genomic DNA was performed with SmaI and the fragments were separated by pulsed-field gel electrophoresis. Only six different RFLP patterns were demonstrated among 30 MRSA isolates. Isolates possessing an identical RFLP pattern were demonstrated in eight of the nine Sao Paulo hospitals evaluated. Our results documented the widespread dissemination of a single clone of MRSA in several hospitals. Furthermore, the small clonal variability among multidrug-resistant MRSA coupled with the wide spread of this clone could make the intrahospital epidemiological evaluation of RMSA outbreaks very difficult.