Uncovering Infant Group B Streptococcal (GBS) Disease Clusters in the United Kingdom and Ireland Through Genomic Analysis: A Population-based Epidemiological Study

Simon M Collin, Natalie Groves, Catherine O'Sullivan, Elita Jauneikaite, Darshana Patel, Robert Cunney, Mary Meehan, Arlene Reynolds, Andrew Smith, Diane Lindsay, Lorraine Doherty, Eleri Davies, Victoria Chalker, Peter Lamb, Baharak Afshar, Sooria Balasegaram, Juliana Coelho, Derren Ready, Colin S Brown, Androulla EfstratiouKirsty Le Doare, Shiranee Sriskandan, Paul T Heath, Theresa Lamagni

Research output: Contribution to journalArticle (Academic Journal)peer-review

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BACKGROUND: The true frequency of hospital outbreaks of invasive group B streptococcal (iGBS; Streptococcus agalactiae) disease in infants is unknown. We used whole genome sequencing (WGS) of iGBS isolates collected during a period of enhanced surveillance of infant iGBS disease in the UK and Ireland to determine the number of clustered cases.

METHODS: Potentially linked iGBS cases from infants with early (<7 days of life) or late-onset (7-89 days) disease were identified from WGS data (HiSeq 2500 platform, Illumina) from clinical sterile site isolates collected between 04/2014 and 04/2015. We assessed time and place of cases to determine a single-nucleotide polymorphism (SNP) difference threshold for clustered cases. Case details were augmented through linkage to national hospital admission data and hospital record review by local microbiologists.

RESULTS: Analysis of sequences indicated a cutoff of ≤5 SNP differences to define iGBS clusters. Among 410 infant iGBS isolates, we identified 7 clusters (4 genetically identical pairs with 0 SNP differences, 1 pair with 3 SNP differences, 1 cluster of 4 cases with ≤1 SNP differences) of which 4 clusters were uncovered for the first time. The clusters comprised 16 cases, of which 15 were late-onset (of 192 late-onset cases with sequenced isolates) and 1 an early-onset index case. Serial intervals between cases ranged from 0 to 59 (median 12) days.

CONCLUSIONS: Approximately 1 in 12 late-onset infant iGBS cases were part of a hospital cluster. Over half of the clusters were previously undetected, emphasizing the importance of routine submission of iGBS isolates to reference laboratories for cluster identification and genomic confirmation.

Original languageEnglish
Pages (from-to)e296-e302
JournalClinical Infectious Diseases
Issue number9
Publication statusPublished - 4 May 2021

Bibliographical note

© Crown copyright 2020.


  • Disease Hotspot
  • Epidemiologic Studies
  • Genomics
  • Humans
  • Infant
  • Ireland/epidemiology
  • Streptococcal Infections/epidemiology
  • Streptococcus agalactiae/genetics
  • United Kingdom/epidemiology


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