Leukocidin - a substance produced by staphylococci; has a toxic effect on leukocytes. The ability to produce leukocidin depends on the virulence of the culture.
There are three types of leukocidin: the first acts on rabbit leukocytes; the second has a toxic effect on the rabbit and human leukocytes and does not affect the guinea pig, mouse and sheep leukocytes; the third has a negative effect on the leukocytes of a human, rabbit, guinea pig and mouse, and is not active in relation to the white blood cells of a ram. The toxic effects of various types of leukocidin range from minor morph damage, leukocyte structures to complete lysis of white blood cells. Leukocydine-killed leukocytes lose their ability to regenerate (discolor) methylene blue. This is the basis of the “bioscopic” method for determining leukocidin. Pathogenic staphylococci produce leukocidin with a titer from 1: 200 to 1: 1000 (according to the “bioscopic” method). Serum of animals immunized with staphylococci acquires the ability in vitro to neutralize leukocidin.
See also Staphylococcus.