Opacity Factor Inhibition Test for Typing Group A Beta-Haemolytic Streptococcus Strains and Antibiotic Susceptibility

Serum Opacity Factor (OF) inhibition test was used to analyse group A beta-haemolytic streptococcus strains (GABHS) which were isolated from clinical specimen in Beijing Children’s Hospital (BCH). A total of 110 strains were tested, thirty per cent (33/110) of these isolates were OF(+). The distribution of serotypes for OF(+) strains was M68, M75, M60, PT2841, M22, respectively. The serotypes M68 and M75 were accounted for 66.6%. All of M68 strains were isolated from the patients wiht pharyngitis and scarlet fever. Most isolates fron cases with impetigo were M75. These results suggest that there is a different distribution in M/OF serotyping between China and other European/American countries. It is possible that there might be an epidemic of serotypes M68, M75 in Beijing areas. To characterize group A streptococcus, it is necessary to do other serotyping studies further besides M/OF typing.