We have characterized the heat-shock response of the nosocomial pathogen Enterococcus faecium. The growth of E. faecium cells was analyzed at different temperatures; little growth was observed at 50degreesC, and no growth at 52degreesC or 55degreesC. In agreement, a marked decrease of general protein synthesis was observed at 52degreesC, and very light synthesis was detected at 55degreesC. The heat resistance of E. faecium cells was analyzed by measuring the survival at temperatures higher than 52degreesC and, after 2 h of incubation, viable cells were still observed at 70degreesC. By Western blot analysis, two heat-induced proteins were identified as GroEL (65 kDa) and DnaK (75 kDa). Only one isoform for either GroEL or DnaK was found The gene expression of these heat-shock proteins was also analyzed by pulsed-labeled experiments The heat-induced proteins showed an increased rate of synthesis during the first 5 min, reaching the highest level of induction after 10 min and returning to the steady-state level after 20 min of heat treatment.