Introduction: A previous study has reported the prevalence of Streptococcus pyogenes (Strep A) to be 21% amongst children presenting with a sore throat at local clinics in South Africa. Knowledge of local prevalence and emm typing is essential to guide resources, awareness campaigns, training of health care workers and vaccine development. This research, representing a follow-up to an earlier study conducted 15 years previously, investigates Strep A infection in participants at high risk for rheumatic heart disease.
Methods: The study is a prospective longitudinal evaluation of Strep A-positive throat cultures in participants aged 5 to 17 years in Vanguard, Cape Town collected over a three-year period. Participants were evaluated at baseline and every 2 months, over a 24-month period of observation, with serial throat cultures taken for emm-typing.
Results: 256 participants have been enrolled and 858 throat cultures were collected, from whom 124 positive β-haemolytic Streptococcus (14.5%) were isolated. Twenty-one percent of participants had Strep A on enrolment with a further 29 Strep A isolates recovered from asymptomatic participants during the follow-up period. Characterization of isolates revealed 27 different emm types: emm1 (n=10), emm12 (n=7) and emm49 (n=6) and emm clusters E3 (n=19), A-C3 (n=10) and E6 (n=8). The putative 30-multivalent vaccine would grant protection for only 61.8% (n=42) of Strep A isolates; however, due to cross protection this would increase to 70.6% (n=48).
Conclusions: While the prevalence of Strep A in pharyngitis remains the same, these results show a different pattern of emm-type distribution than in the previous study.