A national outbreak of Serratia marcescens complex: investigation reveals genomic population structure but no source, Norway, June 2021 to February 2023

We report a national outbreak of Serratia marcescens complex type 755 (ct755) in Norway, with 74 cases identified between June 2021 and February 2023. Careful reviews of patient journals and interviews were performed, involving 33 hospitals throughout Norway. All available clinical isolates of S. ma...

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Main Author: The Norwegian Serratia study group
Format: Article
Language:English
Published: European Centre for Disease Prevention and Control 2025-02-01
Series:Eurosurveillance
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Online Access:https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2025.30.5.2400291
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author The Norwegian Serratia study group
author_facet The Norwegian Serratia study group
author_sort The Norwegian Serratia study group
collection DOAJ
description We report a national outbreak of Serratia marcescens complex type 755 (ct755) in Norway, with 74 cases identified between June 2021 and February 2023. Careful reviews of patient journals and interviews were performed, involving 33 hospitals throughout Norway. All available clinical isolates of S. marcescens collected between January 2021 and February 2023 (n = 455, including cases) from all involved hospitals were whole genome sequenced. Cases displayed a pattern of opportunistic infections, as usually observed with S. marcescens. No epidemiological links, common exposures or common risk factors were identified. The investigation pointed to an outbreak source present in the community. We suspect a nationally distributed product, possibly a food product, as the source. Phylogenetic analysis revealed a highly diverse bacterial population containing multiple distinct clusters. The outbreak cluster ct755 stands out as the largest and least diverse clone of a continuum, however a second cluster (ct281) also triggered a separate outbreak investigation. This report highlights challenges in the investigation of outbreaks caused by opportunistic pathogens and suggests that the presence of identical strains of S. marcescens in clinical samples is more common than previously recognised.
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spelling doaj-art-0f0e052f55b24e02b4e8db387de412522025-08-20T03:41:01ZengEuropean Centre for Disease Prevention and ControlEurosurveillance1560-79172025-02-0130510.2807/1560-7917.ES.2025.30.5.2400291http://instance.metastore.ingenta.com/content/eurosurveillance/30/5A national outbreak of Serratia marcescens complex: investigation reveals genomic population structure but no source, Norway, June 2021 to February 2023The Norwegian Serratia study group0The members of The Norwegian Serratia study group are listed under collaboratorsWe report a national outbreak of Serratia marcescens complex type 755 (ct755) in Norway, with 74 cases identified between June 2021 and February 2023. Careful reviews of patient journals and interviews were performed, involving 33 hospitals throughout Norway. All available clinical isolates of S. marcescens collected between January 2021 and February 2023 (n = 455, including cases) from all involved hospitals were whole genome sequenced. Cases displayed a pattern of opportunistic infections, as usually observed with S. marcescens. No epidemiological links, common exposures or common risk factors were identified. The investigation pointed to an outbreak source present in the community. We suspect a nationally distributed product, possibly a food product, as the source. Phylogenetic analysis revealed a highly diverse bacterial population containing multiple distinct clusters. The outbreak cluster ct755 stands out as the largest and least diverse clone of a continuum, however a second cluster (ct281) also triggered a separate outbreak investigation. This report highlights challenges in the investigation of outbreaks caused by opportunistic pathogens and suggests that the presence of identical strains of S. marcescens in clinical samples is more common than previously recognised.https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2025.30.5.2400291ct755WGSoutbreakclonalitySerratia marcescenswhole genome sequencing
spellingShingle The Norwegian Serratia study group
A national outbreak of Serratia marcescens complex: investigation reveals genomic population structure but no source, Norway, June 2021 to February 2023
Eurosurveillance
ct755
WGS
outbreak
clonality
Serratia marcescens
whole genome sequencing
title A national outbreak of Serratia marcescens complex: investigation reveals genomic population structure but no source, Norway, June 2021 to February 2023
title_full A national outbreak of Serratia marcescens complex: investigation reveals genomic population structure but no source, Norway, June 2021 to February 2023
title_fullStr A national outbreak of Serratia marcescens complex: investigation reveals genomic population structure but no source, Norway, June 2021 to February 2023
title_full_unstemmed A national outbreak of Serratia marcescens complex: investigation reveals genomic population structure but no source, Norway, June 2021 to February 2023
title_short A national outbreak of Serratia marcescens complex: investigation reveals genomic population structure but no source, Norway, June 2021 to February 2023
title_sort national outbreak of serratia marcescens complex investigation reveals genomic population structure but no source norway june 2021 to february 2023
topic ct755
WGS
outbreak
clonality
Serratia marcescens
whole genome sequencing
url https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2025.30.5.2400291
work_keys_str_mv AT thenorwegianserratiastudygroup anationaloutbreakofserratiamarcescenscomplexinvestigationrevealsgenomicpopulationstructurebutnosourcenorwayjune2021tofebruary2023
AT thenorwegianserratiastudygroup nationaloutbreakofserratiamarcescenscomplexinvestigationrevealsgenomicpopulationstructurebutnosourcenorwayjune2021tofebruary2023