Effect of Partially Purified Streptococcal M Protein on the In Vitro Phagocytosis ofStreptococcus pyogenes

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Abstract
Domingue, GeraldJ. (Tulane University, New Orleans, La.),and William A. Pierce, Jr. Effect of partially purified streptococcal M protein on the in vitro phagocytosis ofStreptococcus pyogenes. J. Bacteriol.89:583–588. 1965.—M protein fromStreptococcus pyogenesstrain Bailey type 12 was adsorbed onto cells of a glossy mutant of this strain. Phagocytosis experiments were performed in vitro with rabbit peritoneal polymorphonuclear leukocytes. Direct microscopic counts suggested M protein-treated cells were more resistant to phagocytosis than were untreated cells. With the Cohn and Morse technique for evaluating quantitatively the fate of bacteria during phagocytosis, there was observed a more rapid drop in total and extracellular counts of treated, as compared with untreated, cells. Experiments with radioactively labeled streptococci showed that M-treated cells were more readily destroyed within leukocytes than were nontreated glossy streptococci, which suggested a reason for the scarcity of treated streptococci in direct microscopic counts.