Studies on the Pathogenicity of Group a Streptococci

Abstract

Four strains of Group A streptococci, possessing different degrees of virulence for both mice and rats, were tested for susceptibility to phagocytosis on glass slides, in glass roller tubes, and on the surfaces of freshly excised tissues and moistened filter paper. All of the tests were performed in the absence of serum to exclude the possible presence of opsonins. Only under conditions which allowed surface phagocytosis to take place was there a correlation between virulence and susceptibility to phagocytosis. A similar relationship between virulence and surface phagocytosis was also demonstrable in vivo during the early stages of experimental streptococcal peritonitis. Systematic study of the evolution of the peritonitis revealed that its outcome was determined by the phagocytic reaction which occurred in the first few hours of the infection.

Studies on the Pathogenicity of Group a Streptococci

“…They included: (a) the matt (M) and glossy (G) variants of Strain $23, both of which form large capsules, but only one of which (matt) produces detectable amounts of M protein (Table I), and (b) the matt virulent Strain T14/'46 and its avirulent variant, T14 (Table II), both of which form capsules smaller than those of the $23 strains, and one of which (T14) produces less M antigen than the other (T14/46). The relative virulences of the four strains, when injected intraperitoneally in both mice and rats, vary over a relatively wide range and rank in the following order: $23M (most virulent), T14/46, $23G, and T14 (see Table I of previous paper (8)). The methods used in culturing these strains and in studying their capsules, their production of M protein and their susceptibility to phagocytosis have already been described (8).…”

“…Streptococcal Cultures.--The four strains of Group A streptococci studied were the same as those used in the preceding experiments (8). They included: (a) the matt (M) and glossy (G) variants of Strain $23, both of which form large capsules, but only one of which (matt) produces detectable amounts of M protein (Table I), and (b) the matt virulent Strain T14/'46 and its avirulent variant, T14 (Table II), both of which form capsules smaller than those of the $23 strains, and one of which (T14) produces less M antigen than the other (T14/46).…”

“…Numerous strains have been described, for example, which appear to produce abundant amounts of M protein and yet are relatively avirulent for mice (1,(11)(12)(13)(14). Others possessing large capsules have, likewise, been found to be lacking in virulence (3,15), as illustrated by the glossy variant of the $23 strain referred to in the accompanying paper (8). Indeed, it has been shown that streptococci which produce both capsules and M substance also may lack pathogenicity for mice.…”

“…(Received for publication, June 29, 1959) There is abundant experimental evidence that both the M protein and the capsular gel of Group A streptococci play significant roles in pathogenicity (1)(2)(3)(4)(5)(6)(7). That they enhance virulence by interfering with surface phagocytosis is indicated by the observations described in the preceding paper (8).…”

“…Indeed, it has been shown that streptococci which produce both capsules and M substance also may lack pathogenicity for mice. The T14 strain, used in this and the previous study, is just such an organism (8).…”