The application of environmental health assessment strategies to detect Streptococcus pyogenes in Kimberley school...

Children spend almost one-third of their waking hours at school. Streptococcus pyogenes (Strep A) is a common childhood bacterial infection that can progress to causing serious disease. We aimed to detect Strep A in classrooms by using environmental settle plates and swabbing of high-touch surfaces in two remote schools in the Kimberley, Western Australia.

Twelve classrooms in two schools participated in 2021 and 2022. Seven horse-blood agar plates containing colistin and nalidixic acid (HBA-CNA) were placed in each occupied classroom at varied heights for 4 h, and 20 high-touch items were swabbed and later cultured on HBA-CNA plates. The primary outcome of each sample was presence or absence of Strep A. Identified Strep A isolates were whole genome sequenced (WGS) to assess for similarity between host-derived and environmental strains.

During two visits to each participating Kimberley school in June 2021 and September 2022, the point prevalence of Strep A positive throat swab ranged between 3/34 (8.8 %) and 5/21 (23.8 %); Strep A impetigo was lower at between 0/43 (0 %) and 2/23 (8.7 %). Strep A was detected from 4/240 (2 %) environmental swabs collected across 3/12 (25 %) classrooms but not cultured from any of the classroom settle plates. Whole genome sequencing identified environmental emm types to also be those strains in circulation.

There was little evidence to support fomite, droplet or airborne Strep A in classrooms as major modes of transmission among children. Further work is required to determine if classrooms play a role in the transmission of Strep A between students.