Streptococcus pyogenes is believed to be mostly transmitted through direct human contact or contaminated fomites. Policies to control spread of S. pyogenes in schools and hospitals are largely based on expert opinion, single outbreaks, and historical studies. Systematic sampling during school outbreaks, however, suggests fomite contamination may be infrequent, pointing to a distinct role for dispersal of S. pyogenes in air. We undertook an experimental study to evaluate aerosolisation competence and desiccation tolerance of S. pyogenes in comparison with seven other bacterial pathogens: Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecium, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter hormaechei.
Bioaerosols containing each species (n=3 isolates per species) were generated using a stirring bioaerosol system and aerosolisation competence was evaluated using agar settle plates or an Andersen Cascade Impactor. Cell surface hydrophobicity (CSH) was measured using the Microbial Adhesion To Hydrocarbon method. All species were inoculated onto a polystyrene surface and survival under desiccated conditions was monitored in ambient conditions for 28 days.
S. pyogenes survived poorly on polystyrene compared to all species, with only 0.02% cells remaining viable after 3 days. This suggests fomite-mediated transmission of S. pyogenes may be limited by poor desiccation tolerance, with relevance to infection control policies. Contrastingly, S. pyogenes was preferentially aerosolised relative to all species except S. aureus. Entry into aerosol positively correlated with CSH amongst all species suggesting that the risk of aerosol transmission may vary between bacterial species. The role of S. pyogenes surface hydrophobicity in aerosolisation from the respiratory tract is under investigation.