Streptococcus Leucocidin and the Resistance of Clasmatocytes.

Abstract

Although long known (Ruediger 1 ), the leucocyte destroying properties of virulent hemolytic streptococci have never been as fully investigated as they deserve. We agree with McLeod 2 that leucocidin formation is perhaps the most important factor in the virulence of this micro-organism. We have recently undertaken a more complete analysis of leucocidin which we believe is the first since that of Channon and McLeod. 3 The only other study that is at all complete is that of Nakayama. 4

The presence of leucocidin in a broth culture of streptococcus is evidenced by the demonstrable disintegration of leucocytes that are exposed to it, or better, by interference with the oxygen absorption of these cells when living as contrasted by its absence when they are dead. This change is delicately measured by the methylene blue bioscopic test of Neisser and Wechsberg.

The precise mode of action of leucocidin under conditions of infection has not been made clear. In our opinion it is operative primarily within the leucocytes that have already ingested streptococci and for this and other reasons is separable from the negatively chemotactic substances known as “virulins” and aggressins. Nakayama believed the leucocidin separate from the hemotoxin also liberally produced by the streptococcus but Channon and McLeod question this. In our experiments leucocidin seems clearly separable from hemotoxin. In the first place leucocidin is not present in many hemolytic or hemotoxin-forming streptococci.