Serratia marcescens bacteremia - an indicator for outbreak management and heightened surveillance

Colonization of neonatal intensive care units by Serratia marcescens is associated with clinical outbreaks. We report the management of an outbreak in a newborn services unit (NBS), in 2004, of a strain of S. marcescens that was present in the unit from 1994. Over the 10-year period, increases in clinical isolates demonstrated three epidemic curves, each spanning 3-4 years and each involving positive blood cultures. In 2004, clinical isolates of S. marcescens bacteremia prompted an investigation. Control measures including screening, creation of a separate unit, use of contact precautions, education, environmental sampling, strategies to reduce overcrowding, surveillance and molecular epidemiological techniques were implemented. In total, 99 babies were either colonized or infected with S. marcescens between December 2003 and December 2005. Isolates were tested with ribotyping identifying one main endemic strain. No environmental source was found, however, the outbreak terminated following adherence to infection control principles. Epidemiological information, structural and practice changes were used to prevent transmission and control the outbreak.