Characteristics of Serratia marcescens Bacteremia in Comparison to Other Gram-Negative Bacteremia in Infants in the Pediatric Cardiac Intensive Care Unit A Case-Control Study (2012-2022)

Purpose: Serratia marcescens is a well-recognized hospital-acquired pathogen frequently implicated in outbreaks in neonatal and pediatric intensive care units. We compared clinical characteristics of infants with Serratia bloodstream infections (BSI) to those with non-Serratia gram-negative BSI. Methods: A retrospective case-control study comparing infants (0-2 y/o) hospitalized at our referral pediatric cardiac intensive care unit (PCICU), who acquired gram-negative blood cultures, during 2012–2022. Patients were categorized into two groups: S. marcescens BSI versus non-Serratia gram-negative BSI. Demographic and clinical data were extracted from our medical databases. Results: Of 112 patients meeting inclusion criteria, 40 (36%) had Serratia BSI and 72 (64%) non-Serratia gram-negative BSI. Blood stream infection with Serratia occurred later postoperatively (median 15 vs 7 days, p < .01), were associated with less pre-infection inotropic support (median VIS 0 vs 5, p < .01) and higher rates of multisite involvement (35% vs 18%, p = .04). Duration of indwelling vascular catheters at time of infection was longer in the Serratia group (median 10 vs 7 days, p = .03). No associated mortality was attributed to Serratia BSI, as compared to a 5.6% mortality rate in the non-Serratia group. Conclusions: Serratia BSI in the PCICU tends to develop later during hospitalization, involves more multiple infection sites, and is associated with longer vascular catheters dwell durations at the time of infection. Serratia infections appeared sporadically throughout the year without seasonal clustering. This supports the importance of stringent infection control practices and warrants prospective studies on prevention strategies.