G. RUZO, B. M. WILLEY, A. FAMIGLIETTI, C. VAY, A. MCGEER, D. E. LOW. Mount Sinai and Princess Margaret Hospitals, University of Toronto, Toronto, Ontario, Canada; and Nuestra Senora De Lujan and Hospital de Clinicas, Buenos Aires, Argentina.

OBJECTIVE: In 1996, it was reported that 65% of Staphylococcus aureus isolated from hospitalized patients throughout Argentina were resistant to methicillin. This study was designed to investigate the relatedness between clinical MRSA isolates obtained from infected patients in the University Hospital in Buenos Aires between 1995 and 1998. As well, it aimed to determine whether any Argentinean MRSA clone had previously been identified in Canada.

METHODS: A total of 56 MRSA (42 sterile site, 3 urine, 3 respiratory, 3 catheter tips, 5 wound) were selected: 14 from 1995, 2 from 1996, 21 from 1997 and 19 from 1998. These were compared to >1000 Canadian strains using standard SmaI pulsed field gel electrophoresis (PFGE).

RESULTS: PFGE identified 7 unique clones among the Argentinean MRSA: 31 (55%) were type A, 16 (29%) type B, 4 (7%) type C, 2 (4%) type D, and one each of E, F and G. Predominant clones A and B were observed at a constant rate between 1995 and 1998. Clonality was established between Argentinean PFGE type B MRSA and one North American clone. This North American clone is the 2^nd most common in Ontario, accounting for 35% of MRSA between 7-12/95, 23% during 1-6/96, 14% during 7-12/96 and 15% during 1997. It was one of the earliest MRSA identified by our laboratory from Ontario and has been identified in institutions from coast to coast across Canada and the United States. No other common strains were identified.

CONCLUSIONS: Limited diversity was found among the Argentinean MRSA with the identification of only a few epidemic clones, as is the case among Canadian strains. However, evidence was found of the dissemination of one major clone through both south and north America.

Presented at:

CANADIAN ASSOCIATION FOR CLINICAL MICROBIOLOGY AND INFECTIOUS DISEASES (CACMID) 66^th Conjoint Meeting on Infectious Diseases, Toronto, ON, Canada, Nov 8 – 12, 1998