Streptococcal group A, C and G pharyngitis in school children: a prospective cohort study in Southern India.

Diagnosing streptococcal pharyngitis in children on the basis of clinical appearance and throat culture is complicated by high colonisation rates and by the ability of other pathogens to cause clinically similar disease. To characterise the epidemiology of Lancefield Group A, C and G β-haemolytic streptococcus (GAS, GCS and GGS, respectively) in children, we conducted a 2-year prospective study of 307 school children between 7 and 11 years old. GGS and GAS were commonly identified organisms both for silent streptococcal colonisation and symptomatic sore throat, while GCS was uncommonly found. Streptococcal culture positivity at the time of clinical pharyngitis was estimated to reflect true streptococcal pharyngitis in only 26% of instances, with the frequency varying from 54% for children rarely colonised to 1% for children frequently colonised. Numerous GAS emm types were identified, including several types previously associated with severe pharyngitis (e.g. emm types 1, 3 and 28). No severe complications were seen in any child. These data suggest that the clinical diagnosis of streptococcal pharyngitis is likely to remain difficult and that treatment decisions will remain clouded by uncertainty. There remains a need for organism-specific rapid point-of-care streptococcal diagnostic tests and tests that can distinguish between streptococcal colonisation and disease.