Table 1.

Study objectives and outcomes

	Objective(s)	Outcome(s)/endpoint(s)
Primary	To determine the minimum plasma penicillin concentration required to prevent acute symptomatic Streptococcus pyogenes pharyngitis following a direct oropharyngeal challenge with S. pyogenes M75.	Development of S. pyogenes pharyngitis during confinement period, according to a predefined clinical and laboratory criteria.
Secondary	1. To identify the target plasma penicillin concentration required to prevent S. pyogenes colonisation of the pharynx.	Development of S. pyogenes colonisation following the challenge, defined as S. pyogenes M75 isolation from throat swab in the absence of signs and symptoms of clinical pharyngitis after completing antibiotic treatment at the conclusion of confinement period.
	2. To identify the target salivary penicillin concentration required to prevent S. pyogenes pharyngitis or colonisation.	Assays to detect penicillin concentration in saliva from all participants.
Exploratory	1. To characterise plasma humoral and cellular immunological profiles of immune response to experimental challenge with S. pyogenes in healthy participants.	Laboratory assays to measure immunological and inflammatory responses to the challenge.
	2. To characterise plasma inflammatory (CRP and procalcitonin) and metabolomic profiles of S. pyogenes pharyngitis.	Measurement of inflammatory markers from blood samples.
	3. To identify whether Cystatin C-based markers of renal function improve estimates of penicillin G renal clearance compared with creatinine-based measures.	Measurement of Cystatin-C from blood samples.
	4. To explore microbiological and local factors associated with S. pyogenes adhesion to tonsillar mucosa.	Laboratory assays to measure mucosal response.
	5. To explore S. pyogenes transcriptomic changes in response to penicillin exposure in S. pyogenes pharyngitis.	Transcriptomic analyses/genetic sequencing of S. pyogenes isolates.
	6. To investigate potential environmental contamination of S. pyogenes via large respiratory droplets, airborne small respiratory droplets and surface contact.	Microbiological and culture analysis of participants’ contact surfaces and surroundings.
	7. To explore motivations, attitudes and experiences of participating in clinical trials and human challenge studies.	Responses to questionnaires administered during study period by participants.