T-typing of group A streptococci from clinical specimens: restriction of the number if implied M types in each T-pattern by tests for opacity factor and nicotinamide adenine dinucleotide glycohydrolase.

117 group A streptococci, consecutively isolated from routine throat swab cultures, were T-typed and further characterized according to their enzyme reactions. The results of typing with two different commercial kits of anti-T sera showed good agreement. 89 per cent of the strains were typable by either of these kits. 68 per cent of the strains were OF-positive and 95 per cent NADse-positive. With T-typing alone, 22 per cent of the strains showed agglutination patterns implying only one M type each. When considered together, the T-typing and enzyme reactions made it possible to implicate one M type only for each of 45 per cent of the strains. In a further 34 per cent of the strains, the possible M type of each strain was restricted to four types. However, these findings were hampered by the fact that the T patterns of a number of more seldom met group A streptococci have not been investigated adequately.