Despite the fact that group A streptococci (GAS) remain susceptible to penicillin V (pen V), an increasing rate of bacteriological treatment failures has occurred. A recent study has suggested that the major variables associated with pen V treatment failures were the number of days ill prior to initiation of treatment (<2 days) and age <6 years. In order to study the link between pen V treatment failures and individual variables, we reviewed the files of all children enrolled in four randomised multicentre trials of oral antibiotic therapy, carried out from 1993 to 1999. A standard protocol and follow-up examination were used in these four studies: cultures were obtained 4 days and 1 month after completion of treatment. Total DNA restriction fragment length polymorphism was used to compare pre- and post-treatment GAS isolates. We enrolled 1560 children aged 3 to 12 years, 685 received a 10 day pen V regimen (45 mg/kg per day divided into three doses/day), among them 536 were assessable for bacteriological efficacy at the first and second follow-up visit. We found the only variable associated with penicillin treatment failure was the age of the child when infected. The rate of failure was statistically more important for children younger than 6 years (35.5%, 95% CI 29.9--41.1) than for older children (21.9%, 95% CI 16.9-26.9).
Conclusion: in this study only young age (<6 years) increases penicillin V treatment failures for group A streptococcal tonsillopharyngitis. This may lead to different antibiotic regimens and follow-up modalities for these targeted patients.