Case-control analysis of endemic serratia marcescens bacteremia in a neonatal intensive care unit

Abstract

Background: Serratia marcescens is an opportunistic gram-negative rod which typically infects compromised hosts.

Objectives: To identify risk factors, signs, and outcomes associated with non-epidemic S. marcescens bacteremia in a neonatal intensive care unit (NICU).

Methods: The records of infants with S. marcescens bacteremia while in the Yale-New Haven Hospital NICU from 1980-2004 were reviewed. A matched case-control study was performed by comparing each case of S. marcescens to 2 uninfected controls and 2 cases of Escherichia coli bacteremia.

Results: Twenty-five sporadic cases of S. marcescens bacteremia were identified. Eleven available isolates were determined to be different strains by pulse field gel electrophoresis. Infants with S. marcescens bacteremia had median gestational age and birth weight of 28 weeks and 1235 grams, respectively. Compared to matched, uninfected controls, infants with S. marcescens bacteremia were more likely to have had a central vascular catheter (OR=4.33; 95%CI:[1.41,13.36]) and surgery (OR=5.67; 95%CI:[1.81,17.37]), and had a higher overall mortality (44% v. 2%; OR=38.50; 95%CI: [4.57,324.47]). Compared to E. coli matched controls, infants with S. marcescens bacteremia had later onset of infection (median of 33 days of life v. 10; p<0.001), prolonged intubation (OR=5.76; 95%CI:[1.80,18.42]), and a higher rate of CVC (OR=7.77; 95%CI:[2.48,24.31]) use at the time of infection. A higher rate of meningitis (24% v. 7%; OR=3.98; 95%CI:[1.09,14.50]) was observed with S. marcescens bacteremia compared to E. coli.

Conclusions: S. marcescens bacteremia occurs sporadically in the NICU, primarily in premature infants requiring support apparatus late in their hospital course. Associated meningitis is common and mortality high.