Serratia Infection Epidemiology Among Very Preterm Infants in the Neonatal Intensive Care Unit.

Background: Serratia spp. are opportunistic, multidrug resistant, Gram-negative pathogens, previously described among preterm infants in case reports or outbreaks of infection. We describe Serratia late-onset infection (LOI) in very preterm infants in a large, contemporary, nationally representative cohort.

Methods: In this secondary analysis of prospectively collected data of preterm infants born 401-1500 grams and/or 22-29 weeks gestational age from 2018 to 2020 at 774 Vermont Oxford Network members, LOI was defined as culture-confirmed blood and/or cerebrospinal fluid infection > 3 days after birth. The primary outcome was incidence of Serratia LOI. Secondary outcomes compared rates of survival and discharge morbidities between infants with Serratia and non-Serratia LOI.

Results: Among 119,565 infants, LOI occurred in 10,687 (8.9%). Serratia was isolated in 279 cases (2.6% of all LOI; 2.3 Serratia infections per 1000 infants). Of 774 hospitals, 161 (21%) reported at least one Serratia LOI; 170 of 271 (63%) cases occurred at hospitals reporting 1 or 2 Serratia infections, and 53 of 271 (20%) occurred at hospitals reporting ≥5 Serratia infections. Serratia LOI was associated with a lower rate of survival to discharge compared with those with non-Serratia LOI (adjusted relative risk 0.88, 95% CI: 0.82-0.95). Among survivors, infants with Serratia LOI had higher rates of tracheostomy, gastrostomy and home oxygen use compared with those with non-Serratia LOI.

Conclusions: The incidence of Serratia LOI was 2.3 infections per 1000 very preterm infants in this cohort. Lower survival and significant morbidity among Serratia LOI survivors highlight the need for recognition and targeted prevention strategies for this opportunistic nosocomial infection.