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Dickinson, Harriet and Reacher, Mark and Nazareth, Bernadette and Eagle, Heidi and Fowler, Deirdre and Underwood, Anthony and Chand, Meera and Chalker, Victoria and Coelho, Juliana and Daniel, Roger and Kapatai, Georgia and Al-Shabib, Ali and Puleston, Richard (2018) Whole genome sequencing in the investigation of recurrent invasive Group A streptococcus outbreaks in a maternity unit. Journal of Hospital Infection . ISSN 1532-2939 (In Press)

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Abstract

Background: The clinical manifestations of Group A streptococcus (GAS) – (Streptococcus pyogenes) are diverse, ranging from asymptomatic colonisation to devastating invasive disease. Maternity related clusters of invasive Group A streptococcus (iGAS) infection are complex to investigate and control, especially if recurrent.

Aim: We report on the investigation into three episodes of emm 75 GAS/iGAS infection in maternity patients at one hospital site over a 4 year period, two with monophyletic ancestry.

Methods: The episodes are described, together with whole genome sequence isolate analyses. Single nucleotide polymorphism differences were compared with contemporaneous emm 75 genomes.

Findings: Seven mothers had GAS/iGAS in over a 4 year period, emm 75, S.pyogenes and one had iGAS (in year 4) emm 3, S.pyogenes (subsequently discounted as linked). Three (clinical/screening samples) of the seven babies of emm 75 positive mothers and 3 screened healthcare workers were positive for GAS emm 75. Whole genome sequence similarity suggests a shared ancestral lineage and suggested a common source transmission but directionality of transmission cannot be inferred. However the findings indicate that persistence of a particular clone in a given setting may be long-term.

Conclusions: Occupational health procedures were enhanced, staff were screened and antibiotic therapy provided to GAS positive staff and patients. The definitive source of infection could not be identified, although staff/patient transmission is the most likely route. The pattern of clonal GAS transmission over 4 years suggests long-term persistence of GAS may have occurred.

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