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Recently, a new synergistic hemolysis between S. aureus α-toxin and factors of group A β-hemolytic streptococci, similar to CAMP phenomenon observed between S. aureus β-toxin and group B of streptococci, has been demonstrated (Choi and Yang, 1980). This phenomenon appeared to be one of useful presumptive tests for the primary differentiation of group A streptococci from other groups of β-hemolytic streptococci encountered in human infections as the CAMP test for group B streptococci. However, this new synergistic hemolysis did have a disadvantage that approximately 80%, of group A streptococci gave positive synergistic hemolysis reaction on sheep blood agar but only rarely the strains gave the synergistic hemolysis reaction on human blood agar (Lee et al., 1981). In this study, a sensitivity of the new synergistic hemolysis on human blood agar was studied. An attempt was made to enhance the production of streptococcal factors by the addition of dextrose, sucrose or lactose to human blood agar under the aerobic and microanaerobic (candle jar culture) conditions. Also the effect of each one of these three sugars on the production of α-toxin of S. aureus was investigated. In addition, a comparative sensitivity of synergistic hemolysis reaction, bacitracin susceptibility test and colony inhibition test was evaluated with group A β-hemolytic streptococci. The results are summarized as follows: The addition of dextrose, an inhibitor of streptolysin S, to human blood agar markdely inhibited the hemolytic activity and retarded the growth of colonies of group A streptococci, whereas both sucrose and lactose apparently retarded the growth of colonies but only slightly lowered the hemolytic activity of them. The production of α-toxin of S. aureus was markdely enhanced on the media supplemented with either 1%, dextrose or sucrose, and α-toxin production was further augmented by candle jar culture system, The sensitivity of the synergistic hemolysis reaction was much higer in candle jar culture system than in conventional culture system. However, the addition of one of three sugars to the human blood agar medium completely abolished the synergistic hemolysis reaction. Of 41 strains of group A streptococci tested, 39 strains (98.%) were bacitracin susceptible, 38 strains (92.6%) were sensitive to colony inhibition by dextrose, and 40 strains(97.5%) were positive in synergistic hemolysis reaction. All of group A streptococci that exhibited the synergistic hemolysis reaction were characterised by "crescent-shaped" synergistic hemolysis, while two of 5 strains of group B streptococci gave ’arrowhead-shaped’ synergistic hemolysis. All of the other groups of streptococci tested were negative in these three parameters. This study clearly indicated that the microanaerobic (candle jar culture) condition is essential for the enhancement of the synergistic hemolysis reaction between S. aureus α-toxin and factors of group A β-hemolytic streptococci, and that an advantage of the dual test with the synergistic hemolysis test and bacitracin susceptibility test over the single test with bacitracin test in the presumptive. identification of group A streptococci.
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