The role of group C and group G streptococci in acute pharyngitis in children

Group C streptococci (GCS) and group G β-haemolytic streptococci (GGS) have caused well-documented epidemics of acute pharyngitis in children, but the importance of these organisms in causing endemic or sporadic pharyngitis is uncertain. The heterogeneity of GCS and GGS may obscure the role of certain subtypes, such as the large-colony-forming strains of group C (Streptococcus dysgalactiae subsp. equisimilis) or group G, in endemic pharyngitis. For a 1-year period, children (aged 6 months to 18 years) (n = 2085) who presented with pharyngitis to the children's hospital emergency department and two outpatient offices were enrolled in a cross-sectional study to ascertain the role of large-colony-forming GCS and GGS in acute pharyngitis. Control patients (n = 194) were children who presented to the same locations during the same time period with non-respiratory tract symptoms or to the orthopaedic cast clinic. Throat cultures were obtained by a standard reference method, and swabs were plated on Strep-Selective Agar. Lancefield grouping and species identification was performed on all β-haemolytic isolates. In total, 65 (3%) large-colony-forming GCS and GGS strains were obtained from pharyngitis patients, and three (1.5%) were obtained from the control group (odds ratio 2.0; 95% confidence interval 0.6-6.1). The low isolation rate of large-colony-forming strains of GCS and GGS indicates that even if these organisms are associated with acute, sporadic pharyngitis in paediatric patients, they represent an unusual pathogen.