Serratia marcescens outbreak in a neonatal intensive care unit associated with contaminated donor milk

Abstract

Objective: Investigation of the origin of a Serratia marcescens outbreak in a neonatal intensive care unit. Design: Retrospective case–control study. Setting: Regional level 3 perinatal center in Germany. Patients: This study included 4 S. marcescens–positive and 19 S. marcescens–negative neonates treated between February 1 and February 26, 2019, in the neonatal intensive care unit. Methods: A case–control study was performed to identify the source of the outbreak. The molecular investigation of S. marcescens isolates collected during the outbreak was performed using pulsed-field gel electrophoresis and next-generation sequencing. Results: The retrospective case–control study showed a significant correlation (P < .0001) between S. marcensens infection or colonization and consumption of donor milk that had tested negative for pathogenic bacteria from a single breast milk donor. Pulsed-field gel electrophoresis and next-generation sequencing retrospectively confirmed an S. marcescens strain isolated from the breast milk of this donor as the possible origin of the initial outbreak. The outbreak was controlled by the implementation of an infection control bundle including a multidisciplinary infection control team, temporary nutrition of infants with formula only and/or their mother’s own milk, repeated screening of all inpatients, strict coat and glove care, process observation, retraining of hand hygiene and continuous monitoring of environmental cleaning procedures. Conclusions: Low-level contaminated raw donor milk can be a source of infection and colonization of preterm infants with S. marcescens even if it tests negative for bacteria.

Recent Records on Bacterial Opportunistic Infections via the Dietary Route

“…In a later phase of the outbreak, a fatal case of meningitis occurred because the infant temporarily shared the room with a colonized neonate. WGS highlighted the sequence identity for all the patient and breast milk isolates with the exception of one isolate with only a single nucleotide polymorphism (SNP), confirming the common origin of the isolates [ 37 ].…”

“…The reports described in this review are summarized in Table S1 [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ], where the bacterial groups involved in the illnesses are reported in alphabetical order along where the type of ...…”

“…The type species of the genus, Serratia marcescens , is widespread in the environment and has the ability to cause a variety of infections in immunocompromised individuals, such as nosocomial wound, respiratory, and urinary tract infections; bacteremia; and meningitis with a possibly lethal outcome [ 96 ]. S. marcescens has repeatedly caused outbreaks in NICUs, where the sources of infection are colonized patients, the personnel hands, contaminated infant food, breast pumps and breast milk, medical devices, parenteral nutrition solutions, drugs, and care products [ 37 , 97 ].…”

“…An outbreak was transmitted by contaminated breast pumps and stopped after changing the disinfection procedure. Three consecutive outbreaks in a NICU were caused by the cross-contamination of breast milk, and the colonization of neonates stopped after the reorganization of the procedures in the milk kitchen [ 37 ].…”

“…The pasteurization of donor milk at 62.5 °C for 30 min inactivates relevant pathogens, but the use of unpasteurized donor milk, though not recommended by most international guidelines, has been adopted in several German and Norwegian hospitals to preserve the immunological properties of raw donor milk and the presumptive better effects on child development. This practice can favor the spread of S. marcescens among patients by different means [ 37 ].…”