MOLECULAR DNA ANALYSIS FOR DIFFERENTIATION OF PERSISTENCE OR RELAPSE FROM RECURRENCE IN TREATMENT FAILURE OF STREPTOCOCCUS-PYOGENES PHARYNGITIS

In the evaluation of treatment failure in group A streptococcal pharyn gitis, it is essential to distinguish persistence or relapse with homo logous streptococcal strains from the acquisition of new, unrelated st rains. Randomly amplified polymorphic DNA analysis and restriction fra gment length polymorphism analysis of total DNA were used as epidemiol ogical tools to compare 122 pre- and post-treatment Streptococcus pyog enes isolates obtained from 61 patients, The results obtained by molec ular typing showed that bacteriological failures were due to the origi nal strains in 43 cases (70%) and to new strains in 18 cases (30%). In the present study, restriction fragment length polymorphism analysis of total DNA appeared to be more discriminative than randomly amplifie d polymorphic DNA analysis. Thus, molecular analysis of DNA is an effe ctive way to distinguish recurrence from persistence or relapse and wi ll be useful in assessing the efficacy of new antibiotic treatments.