Isolation rates of Streptococcus pyogenes in patients with acute pharyngotonsillitis and among healthy school children in Iran.

We examined three populations from the Tehran region and the North part of Iran (Gilan), in all more than 5000 individuals, for carriage of Streptococcus pyogenes (group A streptococci; GAS). Children or adults with acute pharyngotonsillitis and healthy school children harboured GAS in 34-1, 20.0 and 21.0%, respectively. Typing of 421 randomly selected isolates showed a predominance of M-types M4, M5, M11, M12, as well as the provisional type 4245; however, many of the isolates were T and M non-typable. Forty-three percent of all strains were opacity factor (OF) negative. The type distribution differed markedly from that reported in 1973-4, when M types 1 and 12 were predominant.