Whole-genome sequencing in the investigation of recurrent invasive group A streptococcus outbreaks in a maternity unit

• Published in: The Journal of hospital infection Vol. 101; no. 3; pp. 320 - 326
• Main Authors: Dickinson, H., Reacher, M., Nazareth, B., Eagle, H., Fowler, D., Underwood, A., Chand, M., Chalker, V., Coelho, J., Daniel, R., Kapatai, G., Al-Shabib, A., Puleston, R.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2019
• Subjects: Adult; Cluster Analysis; Disease Outbreaks; Disease Transmission, Infectious; Female; Genotype; Health Personnel; Hospitals, Maternity; Humans; iGAS; Infant; Infant, Newborn; Maternity; Molecular Epidemiology; Molecular Typing; Mothers; Polymorphism, Single Nucleotide; Streptococcal Infections - epidemiology; Streptococcal Infections - microbiology; Streptococcal Infections - transmission; Streptococcus pyogenes - classification; Streptococcus pyogenes - genetics; Streptococcus pyogenes - isolation & purification; Streptococcus spp; Whole Genome Sequencing; iGAS; Maternity; Streptococcus spp; Whole-genome sequencing
• ISSN: 0195-6701; 1532-2939
• DOI: 10.1016/j.jhin.2018.03.018

The clinical manifestations of group A streptococcus (GAS) (Streptococcus pyogenes) are diverse, ranging from asymptomatic colonization to devastating invasive disease. Maternity-related clusters of invasive GAS (iGAS) infection are complex to investigate and control, especially if recurrent. To investigate three episodes of emm 75 GAS/iGAS infection in maternity patients at one hospital site over a four-year period (two with monophyletic ancestry). The episodes are described, together with whole-genome sequence (WGS) isolate analyses. Single nucleotide polymorphism differences were compared with contemporaneous emm 75 genomes. Over the four-year study period, seven mothers had emm 75 GAS/iGAS and one mother had emm 3 iGAS (in year 4) (subsequently discounted as linked). Three (clinical/screening samples) of the seven babies of emm-75-positive mothers and three screened healthcare workers were positive for emm 75 GAS. WGS similarity suggested a shared ancestral lineage and 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. Occupational health procedures were enhanced, staff were screened, and antibiotic therapy was provided to GAS-positive staff and patients. The definitive source of infection could not be identified, although staff–patient transmission was the most likely route. The pattern of clonal GAS transmission over the four-year study period suggests that long-term persistence of GAS may have occurred.