Isolation in Brazil of NosocomialStaphylococcus aureusWith Reduced Susceptibility to Vancomycin

Abstract

Objective: To evaluate the possible presence of vancomycin-resistantStaphylococcus aureus(VRSA) in a Brazilian hospital.Design: Epidemiological and laboratory investigation of nosocomial VRSAMethods: 140 methicillin-resistantS aureusstrains isolated between November 1998 and October 1999 were screened for susceptibility to vancomycin. The screening was carried out by using brain-heart infusion agar (BHIA) supplemented with 4, 6, and 8 μg/mL of vancomycin. The minimum inhibitory concentration (MIC) determination was carried out as standardized by the National Committee for Clinical Laboratory Standards using the broth macrodilution, agar-plate dilution, and E-test methods.Patients: Hospitalized patients exposed to vancomycin.Results: 5 of the 140 isolates had a vancomycin MIC of 8 μg/mL by broth macrodilution, agar plate dilution, and E-test methods. Four VRSA strains were isolated from patients in a burn unit who had been treated with vancomycin for more than 30 days, and one from an orthopedic unit patient who had received vancomycin treatment for 7 days. Pulsed-field gel electrophoresis characterized four of the VRSA strains as belonging to the Brazilian endemic clone. All five strains were negative forvanA,vanB, andvanC genes by polymerase chain reaction. Transmission electron microscopy of the five strains revealed significantly thickened cell walls. One patient died due to infection caused by the VRSA strain.Conclusions: This is the first report of isolation of VRSA in Brazil and the first report of isolation of multiple VRSA strains from one facility over a relatively short period of time. This alerts us to the possibility that VRSA may be capable of nosocomial transfer if adequate hospital infection control measures are not taken.