Transmission potential of Streptococcus pyogenes during a controlled human infection trial of pharyngitis

• Published in: mSphere 2024-10, Vol.9 (10), p.e0051324
• Main Authors: Enkel, Stephanie L, Wong, Bernadette, Hla, Thel K, Pickering, Janessa, Barnett, Timothy C, Thomas, Hannah M M, Lansbury, Nina, Carapetis, Jonathan R, Osowicki, Joshua, Steer, Andrew, Manning, Laurens, Bowen, Asha C
• Format: Article
• Language: English
• Subjects: acute rheumatic fever; Adult; Anti-Bacterial Agents - pharmacology; Anti-Bacterial Agents - therapeutic use; Coronaviruses; COVID-19; Design; Disease control; Disease transmission; Environmental Microbiology; environmental transmission of microbes; Epidemics; Experiments; Female; Fomites; Health care; human infection study; Humans; Humidity; infection prevention; Infections; Male; Masks; Morbidity; Pathogens; Penicillin; Penicillins - pharmacology; Penicillins - therapeutic use; Pharyngitis; Pharyngitis - microbiology; Polymerase chain reaction; Research Article; rheumatic heart disease; Streptococcal Infections - microbiology; Streptococcal Infections - transmission; Streptococcus infections; Streptococcus pyogenes; Streptococcus pyogenes - drug effects; Streptococcus pyogenes - genetics; Streptococcus pyogenes - isolation & purification; Whole Genome Sequencing; Young Adult
• ISSN: 2379-5042; 2379-5042
• DOI: 10.1128/msphere.00513-24

Controlled human infection (CHI) models can provide insights into transmission of pathogens such as (Strep A). As part of the Controlled Human Infection with Penicillin for (CHIPS) trial, we explored the potential for transmission among participants deliberately infected with the Strep A emm75 strain. Three approaches to understanding transmission were employed: the use of agar settle plates to capture possible droplet or airborne spread of Strep A; measurement of distance droplets could spread during conversation; and environmental swabbing of high-touch items to detect Strep A on surfaces. Of the 60 (27%) CHIPS trial participants across five cohorts, 16 were enrolled in this sub-study; availability of study staff was the primary reason for selection. In total, 189 plates and 260 swabs were collected. Strep A was grown on one settle plate from a participant on the second day, using plates placed 30 cm away. This participant received the placebo dose of penicillin and had met the primary endpoint of pharyngitis. Whole-genome sequencing identified this to be the challenge strain. Strep A was not detected on any swabs. In this small sample of CHI participants, we did not find evidence of Strep A transmission by the airborne route or fomites, and just one instance of droplet spread while acutely symptomatic with streptococcal pharyngitis. Although these experiments provide evidence of minimal transmission within controlled clinical settings, greater efforts are required to explore Strep A transmission in naturalistic settings.IMPORTANCE remains a significant driver of morbidity and mortality, particularly in under-resourced settings. Understanding the transmission modalities of this pathogen is essential to ensuring the success of prevention methods. This proposed paper presents a nascent attempt to determine the transmission potential of nested within a larger controlled human infection model.