Among children with pharyngitis who test positive for group A Streptococcus (GAS), 10%–25% are GAS carriers. Current laboratory methods cannot distinguish acute infection from colonization.
We examined 2 separate longitudinal studies of children with symptomatic pharyngitis associated with a positive GAS throat culture (illness culture). In cohort 1, children presented with pharyngitis symptoms to a clinician, then had follow-up cultures at regular intervals. In cohort 2, throat cultures were performed at regular intervals and with pharyngitis symptoms. Illness cultures were categorized as acute infection or carrier based on follow-up culture results. In cohort 2, carriers were further categorized as a GAS carrier with a new emm-type or a GAS carrier with a previous emm-type based on typing data from prior culture results. For each cohort, symptoms were compared at the time of illness culture between carriers and those with acute infection.
Cohort 1 (N = 75 illness cultures): 87% of the children were classified as acutely infected versus 13% carriers. Carriers were more likely to have upper respiratory (URI) symptoms [odds ratio (OR): 5.5; 95% confidence interval (CI): 1.4–22.1], headache (OR: 6.0; 95% CI: 1.2–40.5) or vomiting (OR: 5.5; 95% CI: 1.2–24.5). Cohort 2 (N = 122 illness cultures): 79% were acutely infected and 21% were carriers. Children determined to be carriers with a previous detected emm-type were more likely to have URI symptoms compared with those with acquisition of a new emm-type.
Children with symptomatic pharyngitis and GAS on throat culture identified as carriers were more likely to present with URI and atypical symptoms than children who were acutely infected.