[The OF characteristics of streptococci group A and immunity to streptococcal infection based on the results of OF and anti-OF tests].

The influence of the OF activity of group A streptococci on their specific pathogenic properties has been shown, which is manifested by increased virulence of these streptococci for children of younger age groups and by a two times higher isolation rate of OF+ strains in tonsillitis than in scarlet fever. The possibility of the indirect evaluation of the content of anti-M-antibodies by the results of the anti-OF test has been revealed, which permits using this test instead of the bactericidal test, more complicated, in the study of immunity to infection induced by group A OF+ streptococci. Among the main methods of laboratory support of epidemiological surveillance on streptococcal infection, the introduction of the highly discriminating OF typing and the anti-OF test into practical use is recommended.