We evaluated an outbreak of Serratia marcescens infections in 24 neonates in a neonatal intensive care unit(NICU).

From January to August, 2004 a nosocomial outbreak of S. marcescens occurred in our NICU. We describe the clinical characteristics of the outbreak and analyse the risk factors for infections with S. marcescens . After the outbreak stopped, 7 isolates from blood were typed using rapid amplified polymorphic DNA analysis(RAPD).

S. marcescens was isolated from 24 neonates, 19 infected and 5 colonized. Seven out of nineteen neonates had bacteremia, 4 had ventilator associated pneumonia, 4 had purulent conjunctivitis, 2 had UTI, 1 had meningitis and 1 had a wound infection. Three neonates died due to S. marcescens infection, 2 of 3 had ventilator associated pneumonia, 1 had meningitis complicated with abscess. The mortality rate of S. marcescens infection was 15.8%. Factors associated with S. marcescens infections were previous antibiotic therapy, indwelling catheter and use of ventilators. The isolated strains were resistant to most antibiotics, but frequently sensitive to imipenem, bactrim and amikacin. RAPD typing results show that at least 3 epidemic strains were related with this outbreak. But one genotype was predominant type in this outbreak. The control measures were instituted and the outbreak stopped within 2 months.

S. marcescens can cause rapidly spreading outbreaks associated with fatal infections in neonates. If S. marcescens is isolated from clinical specimens, meticulous infection control measures and epidemiologic investigations should be done at an early stage of the outbreak.