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

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.