title: Development and performance evaluation of a recombinase polymerase amplification assay for the rapid detection of group B streptococcus.
abstract: BACKGROUND
  Despite the implementation of prevention guidelines, group B Streptococcal (GBS) infection remains a leading cause of sepsis, pneumonia, and meningitis, resulting in significant neonatal morbidity and mortality. Preventive approaches that identify women at risk of transmitting GBS have reduced the incidence of neonatal GBS disease, and dramatically decreased the associated mortality rates. However, there is an on-going requirement for a near-patient diagnostic test for GBS that can be carried out at the time of delivery, ideally in the labour ward setting, particularly for women of unknown GBS colonisation status at the time of delivery.
  
  
  METHODS
  In this study, a Recombinase Polymerase Amplification (RPA) assay was developed and performance evaluated for the detection of group B Streptococcus in vaginal swabs. The assay uses the cAMP factor (cfb) gene of GBS as the target gene. The analytical performance of the assay was evaluated by testing a panel of GBS reference strains and clinical isolates, and non-GBS organisms. The limit of detection was determined and the clinical performance was evaluated by testing 124 vaginal swabs from women with both GBS positive and negative status.
  
  
  RESULTS
  Based on specificity testing carried out the assay was shown to be specific for the target of interest. The limit of detection of the assay was shown to be between six and 12 genome copies and was comparable to that of a real-time PCR assay, both achieving a limit of detection below 12.5 genome copies. The performance of both assays when applied to clinical samples was identical.
  
  
  CONCLUSIONS
  A specific, sensitive RPA assay for GBS was developed. The performance of the assay for testing of clinical samples is within the acceptable range.
authors.affiliation: Molecular Diagnostics Research Group, School of Natural Sciences, National Centre for Biomedical Engineering Science (NCBES), National University of Ireland, Galway, Ireland.
authors.forename: Christina
authors.initials: C
authors.lastname: Clarke
authors.affiliation: Molecular Diagnostics Research Group, School of Natural Sciences, National Centre for Biomedical Engineering Science (NCBES), National University of Ireland, Galway, Ireland. louise.oconnor@nuigalway.ie.
authors.forename: Louise
authors.initials: L
authors.lastname: O'Connor
authors.affiliation: TwistDx Limited, Cambridge, UK.
authors.forename: Heather
authors.initials: H
authors.lastname: Carré-Skinner
authors.affiliation: TwistDx Limited, Cambridge, UK.
authors.forename: Olaf
authors.initials: O
authors.lastname: Piepenburg
authors.affiliation: Molecular Diagnostics Research Group, School of Natural Sciences, National Centre for Biomedical Engineering Science (NCBES), National University of Ireland, Galway, Ireland.
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Smith
keywords: GBS; Group B Streptococcus; Labour; Limit of detection; Near-patient tests; Neonatal infection; Neonates; Point-of-care; Recombinase Polymerase Amplification; Specificity