Serratia marcescens infections in neonatal departments: Description of an outbreak and review of the literature

An outbreak of colonization and infection with Serratia marcescens occurred in a neonatal intensive care unit (NICU). S. marcescens was isolated from five preterm infants (gestational age 25-30 weeks). Two infants developed septicaemia, which were both fatal, and one infant (the presumed index case) had conjunctivitis due to S. marcescens. Two infants were colonized without clinical signs of infection. All infants were treated with antibiotic regimens including ciprofloxacin and gentamicin. The DNA fingerprints of isolates were determined by enterobacterial repetitive intergenic consensus primers by the polymerase chain reaction. This showed that a single strain had spread in the NICU. An extensive investigation pointed to an infant born from a mother with an intra-uterine infection after prolonged rupture of foetal membranes as a presumed source of the outbreak. A reservoir, other than the infected or colonized infants and their immediate vicinity, was not found, with the sole exception of the waste jar of a Na+/K+-analysis apparatus. Containment of the outbreak was achieved by closure of the NICU for new admissions, strict hygienic measures and cohort nursing of the infected and colonized infants. It was considered especially important to handle the infants with gloves, since frequent hand carriage of staff with S. marcescens was found when gloves were not used.