ORIGINAL ARTICLE

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

Matthew J Bizzarro¹, Louise-Marie Dembry³, Robert S Baltimore^2,3 and Patrick G Gallagher¹

¹ Divisions of Perinatal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
² Divisions of Infectious Diseases, Yale University School of Medicine, New Haven, Connecticut, USA
³ Division of Infectious Diseases, Department of Internal Medicine and Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut, USA

Correspondence to:
Correspondence to:
Patrick G Gallagher
Department of Pediatrics, Yale University School of Medicine, 333 Cedar Street, P O Box 208064, New Haven, CT 06520-8064, USA; patrick.gallagher{at}yale.edu

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 to 13.36)) and surgery (OR = 5.67; 95% CI (1.81 to 17.37)), and had a higher overall mortality (44% vs 2%; OR = 38.50; 95% CI (4.57 to 324.47)). Compared to E coli matched controls, infants with S marcescens bacteremia had later onset of infection (median of 33 days of life vs 10; p<0.001), prolonged intubation (OR = 5.76; 95% CI (1.80 to 18.42)), and a higher rate of CVC (OR = 7.77; 95% CI (2.48 to 24.31)) use at the time of infection. A higher rate of meningitis (24% vs 7%; OR = 3.98; 95% CI (1.09 to 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.

Abbreviations: CVC, central vascular catheter; GNR, gram-negative rod; NICU, neonatal intensive care unit; TPN, total parenteral nutrition; Y-NHH, Yale-New Haven Hospital

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