Genotyping of group A streptococcus by various molecular methods.

BACKGROUND & OBJECTIVE: Group A streptococcus (GAS) causes a wide variety of life threatening diseases in developing countries like India. Characterization of GAS is therefore necessary for prevention and control of the disease. Genotypic analysis of GAS is largely lacking from India, therefore an attempt was made to study the genotype distribution of north Indian GAS isolates. METHODS: Sixty clinical isolates of GAS, (52 collected from pharyngitis and 8 from RF/RHD patients) were genotyped by various molecular techniques like restriction enzyme analysis (REA), ribotyping, PCR-ribotyping and random amplification of polymorphic DNA (RAPD). A few isolates were also typed by emm gene sequencing for comparison. RESULTS: REA using Hind III digestion differentiated the isolates into six different patterns. The same isolates were grouped into three ribotypes when analyzed for PCR - ribotyping of 16S- 23S rRNA region. However, RAPD fingerprints generated higher level of discrimination by AP4 and AP5 primers showing 12 rapdemes, followed by AP3, AP2 and API producing 11, 9 and 6 rapdemes respectively. A total of 78 RAPD fragments or rapdemes were generated, of which 48 (62%) were shared and 30 (38%) were unique. These unique RAPD fragments could be used as a genetic marker for identification of GAS. Representative isolates that produced 12 different rapdemes by AP5, on further confirmation by emm typing showed 11 different emm types. INTERPRETATION & CONCLUSION: The finding of our study demonstrated the RAPD profiling to be the most discriminatory for genotyping of group A streptococcus isolates as well as comparable to the most commonly used sophisticated technique of emm typing.

Clinical score card for diagnosis of group A streptococcal sore throat.

OBJECTIVE: Group A beta hemolytic streptococcus (GAS) sore throat primarily occurs among children in 5-15 years age group, and if not treated appropriately causes rheumatic fever/rheumatic heart disease (RF/RHD). Present study was aimed at validation of a clinical scoring system for diagnosis of GAS. METHODS: Five hundred and thirty six children in 5-15 years age group were enrolled by systematic random selection of households from a peri-urban slum of Chandigarh. They were visited fortnightly at their home for one year to record signs and symptoms of cough and cold. Throat swabs were collected in 918 episodes, of which 123 (13.4%) were GAS culture positive. RESULT: Significant association of GAS was found with pain in the throat, enlarged tonsils, pharyngeal erythema and tender cervical lymphadenopathy. According to the percentage positivity of GAS culture, weighted scores were assigned to age of the child, season of occurrence, fever, size of tonsil, pharyngeal erythema and exudate, lymphadenopathy and pain in throat. Combinations of various symptoms and signs gave sensitivity of 86-89% and specificity of 83-89% whereas clinical score of 15 or more had 91% sensitivity and 98% specificity for diagnosis of GAS pharyngitis. CONCLUSION: As the level of clinical acumen and prevalence of GAS may differ in different primary care settings of the country, the proposed scoring system should be validated and adapted to suit local conditions before establishing it in the primary prophylaxis strategy to prevention of RF/RHD.