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Serratia marcescens outbreak in a neonatal intensive care unit associated with contaminated donor milk
Lukas Bechmann1, Ralf Böttger2, Claas Baier3
1Department of Medical Microbiology and Infection Control, Otto-von-Guericke UniversityMagdeburg, Germany.
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.
Insights
Contaminated donor milk, even if testing negative for bacteria, can cause Serratia marcescens outbreaks in neonatal intensive care units. Strict infection control measures are crucial for managing these events.
Area of Science:
- Neonatal Intensive Care Unit (NICU) infections
- Microbiology
- Infection Control
Background:
- Neonatal intensive care units are vulnerable to outbreaks of multidrug-resistant organisms.
- Serratia marcescens is an opportunistic pathogen that can cause severe infections in preterm infants.
Purpose of the Study:
- To investigate the origin of a Serratia marcescens outbreak in a German neonatal intensive care unit.
- To identify the source of infection and guide control measures.
Main Methods:
- Retrospective case-control study design.
- Inclusion of 4 S. marcescens-positive and 19 S. marcescens-negative neonates.
- Molecular analysis using pulsed-field gel electrophoresis and next-generation sequencing.
Main Results:
- A significant correlation was found between S. marcescens infection/colonization and consumption of donor milk from a single, initially negative-testing donor.
- Molecular methods confirmed the donor's breast milk as the likely source of the outbreak.
- Implementation of an infection control bundle successfully controlled the outbreak.
Conclusions:
- Raw donor milk, even with negative bacterial screening, can harbor low levels of S. marcescens, posing a risk to preterm infants.
- Enhanced screening and strict infection control protocols are vital for preventing and managing S. marcescens outbreaks in NICUs.
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