The Virulence of Biochemical Variants of Streptococcus pyogenes

Abstract

SUMMARYTwo biochemical variants were obtained from a strain of Streptococcus pyogenes, type 19. One variant, known as 'starch-positive', always produced amylomaltase, readily forming starch from maltose. The other variant, known as 'starch-negative', did not usually form starch from maltose in the same cultural conditions. The starch-positive variant had low mouse virulence and the starch-negative variant had high mouse virulence. The starch positive variant was avirulent for the rat, but the starch-negative variant had some rat virulence. Both variants had plenty of M antigen in precipitin tests and showed good anti-phagocytic power both in bactericidal tests with human blood and in surface phagocytosis tests with isolated human leukocytes. The mouse virulence of the starchpositive variant was enhanced by casein polypeptide and by human plasma. Starch-positive and starch-negative variants obtained from a type 12 strain also had the same properties.

The Normal Flora of the Human Skin†

“…In spite of much work in many countries there is little precise information on the factors which render some strains of Staph. aureus apparently more successful than others, Williams (1966) suggests that the success of an epidemic staphylococcus, such as phage-type 80/81, may lie in its superior ability in colonizing the skin, rather than in increased toxin production, Crowley (1965) has studied the virulence of 2 bioehemical variants of Streptococcus pyogenes and has found that in strains possessing satisfactory supplies of M-protein, the presence of an enzyme amylomaltase which converts maltose to stareh, is associated with low mouse-virulence. It is of special interest that these starch-forming strains are not infrequently isolated in association with glomerulo-nephritis and rheumatic fever, FUTURE PROSPECTS Enough has been said to indicate how much there is left to learn about the eutaneous ecosystem.…”