Restriction endonuclease analysis of plasmid DNA from methicillin-resistant Staphylococcus aureus: clinical...

To investigate trends in plasmid types of methicillin-resistant Staphylococcus aureus over a 3-year period and determine the clinical impact of plasmid typing.

Restriction endonuclease analysis of plasmid DNA (REAP) was used to type 270 clinical isolates.

A Veterans Affairs Medical Center.

Forty-four different REAP types were identified and, of these, 23 appeared only once. Types designed as V1 and V2 were more commonly found in nosocomial cases than in community-acquired cases (p < .05); whereas the K and D types were more common in isolates from community-acquired cases (p < .05). In 30 (11%) isolates, no plasmid was detected. When combined with epidemiological data, REAP typing revealed 4 small outbreaks that would have been missed using traditional epidemiological methods alone. In large outbreaks involving 10 or more cases, REAP typing data revealed unsuspected patterns of transmission.

Multiple plasmid types were present in this endemic setting. Restriction endonuclease analysis of plasmid DNA was a practical and valuable adjunct to traditional epidemiological methods.