Factors involved in treatment failures following oral penicillin therapy of streptococcal pharyngitis

Among 331 children with group A streptococcal pharyngitis who were treated with a 10 day oral regimen of either sodium nafcillin or penicillin V potassium, there were 39 treatment failures. There was no correlation between the incidence of relapse and patient's age, sex, interval between onset of illness and onset of therapy, history of respiratory tract allergy, compliance in completing therapy, concomitant presence of penicillinase-producing staphylococci, or incidence of homologous streptococci in household contacts. There was, however, a significantly higher incidence of relapse in patients harboring M-typable strains, as compared with patients harboring nontypable strains; this was particularly evident for patients with types 3 and 12 streptococci. Among the relapse group, there was no difference in the bacteriologic outcome of those patients who received a second course of treatment as compared with the patients who were not re-treated.