Background:
There exist over 250 emm-types of Streptococcus pyogenes, each with its own microbiological and virulence profile. Emm-type is determined through sequencing the hypervariable 5’ end of the M protein gene, and is a useful tool for monitoring the epidemiology of S. pyogenes within the community.
Methods:
We performed a pediatric cohort surveillance study, the Sore Throats Melbourne and Perth Study (STAMPS), during which participants aged 3 to 14 years were monitored for one year. Throat swabs were collected at set timepoints, as well as whenever the participant reported a sore throat. Any S. pyogenes samples isolated were whole-genome-sequenced and their emm-type determined.
Results:
A total of 302 throat swabs were positive for S. pyogenes, and amongst these, 19 emm-types were identified. The most common emm-types were 12 (n = 103), 1 (n = 87), 89 (n = 27), 4 (n = 27), and 75 (n = 17). Of these, m89 was the most associated with sore throats (39%) while m75 was the least associated (12%). Some participants carried S. pyogenes in their throat for long periods of time, up to 12 months, and some participants appeared to acquire new pharyngeal infections with the same emm-type.
Conclusion:
Emm-12, 1, 89, 4, and 75 were the predominant emm-types found in the throats in throat swabs of children in urban settings in Australia. Single episodes of S. pyogenes pharyngitis did not appear to immunise against re-infection by the same or different emm-types.