Decline of erythromycin resistance of group A streptococci in Japan.

Six hundred seventy isolates from children with Group A streptococcal infections from 1981 through 1990 were typed serologically and their antibiotic susceptibilities were determined. There were 479 isolates from patients with pharyngitis, 133 from those with scarlet fever, 35 from those with suppurative infection and 23 from those with nonsuppurative disease. The prevalent M serotypes were 12, 4, 1, 3 and 28. None of the 670 isolates were resistant to penicillin G and cephalexin. Resistance rates of isolates to erythromycin and lincomycin was 22.2% in 1981 and 1982, but a marked decrease was noted after 1983 and only one has been resistant since 1986. Nineteen of 21 erythromycin-resistant isolates were M type 12, and two others were M types 4 and 28. Chloramphenicol resistance was similar to that of erythromycin, and the tetracycline resistance rate decreased gradually from 60% to less than 20%.