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NAD‐glycohydrolase (NADase) was purified from culture supernatant fluids of group C streptococci by adsorption on silica gel, chromatography on hydroxyapatite and ion exchange on Mono S column. After inactivation of a chymotrypsin‐like protease, a homogeneous enzyme was isolated with an N‐terminal sequence of VSGKEGKKSDVKYEMTKVMEANATSS‐KEDKHVMHTLDKVM. According to serological methods, the purified enzyme of group C streptococci was identical to the group A enzyme showing a specific activity of 10000000 U mg−1. It did not attack NADH, NADP or NADPH. In addition, a streptodornase was isolated having an N‐terminal sequence of KTVSVNQTYGE.

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The human pathogenic microorganism Streptococcus pyogenes can resist against phagocytic attack of human granulocytes. Streptococcal M protein and hyaluronic acid were identified as virulence factors involved in this protection. So far, no experiments have been reported which describe the contribution of both components together in one system. We used the chicken embryo as an in vivo phagocytosis model to investigate the role of both components on the virulence of streptococci. For this, isogeneic mutants of group A streptococcal strains (GAS) which lack hyaluronic acid capsule (cap-) or M protein (M-) expression were used for infection and their virulence was compared with laboratory strains which had lost their ability to produce one or both virulence factors after long-time laboratory passages on blood agar. The experiments revealed that strains producing both M protein and hyaluronic capsule were highly virulent. Only 1-10 colony-forming units were enough to cause a 50% lethality of 12-day-old chicken embryos. Those strains lacking one of these components showed a significant decrease in virulence. Finally, strains which failed to express either hyaluronic acid or M protein showed an additional tenfold decrease in virulence. This indicates a partial contribution of both M protein and hyaluronic acid to the virulence of GAS in the chicken embryo.

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