OUTBREAK OF PRIMARY BACTEREMIA CAUSED BY AN ENDEMIC STRAIN OF SERRATIA-MARCENENS AT AN INTENSIVE-CARE UNIT

An outbreak of Serratia marcescens bacteremia detected in the intensive care unit (ICU) of a tertiary care center on the last days of October, 1985, is described The rate of primary S. marcescens nosocomial bacteremia during the pre-epidemic period (January-September 1985) was 6.25 per cent, and for the post-epidemic period compared with the epidemic were significantly different (P<0.0001). The outbreak strains belonged to the biotype A8b, wich has been endemic in our hospital. The responsible organism exhibited an unusual antimicrobial resistance pattern associated to the presence of a specific plasmid (greater than 50 kilobases), wich showed similar fragments after restriction endonuclease digestion. No specific risk factors were identified in the case-control study. The outbreak was probably related to a greater influx of infected patients resulting in less careful infection control measures, due to the emergency situation wich suffered the hospital after the earthquakes in 1985. The unusual high rate of blood isolation of S. marcescens at the ICU was the first sign of the outbreak. The prompt reinforcement of infection control policies facilitated its resolution.