Prolonged outbreak of Serratia marcescens in Tartu University Hospital: a case-control study.

Background: The aim of our study was to investigate and control an outbreak and identify risk factors for colonization and infection with Serratia marcescens in two departments in Tartu University Hospital.
Methods: The retrospective case-control study was conducted from July 2005 to December 2006. Molecular typing by pulsed field gel electrophoresis was used to confirm the relatedness of Serratia marcescens strains. Samples from the environment and from the hands of personnel were cultured.
Results: The outbreak involved 210 patients, 61 (29%) developed an infection, among them 16 were invasive infections. Multivariate analysis identified gestational age, arterial catheter use and antibiotic treatment as independent risk factors for colonization and infection with Serratia marcescens. Molecular typing was performed on 83 Serratia marcescens strains, 81 of them were identical and 2 strains were different.
Conclusions: Given the occasionally severe consequences of Serratia marcescens in infants, early implementation of aggressive infection control measures involving patients and mothers as well as the personnel is of utmost importance.