In vitro Effect of Tyrothricin and Tyrocidine Hydrochloride on Polymorphonuclear Leucocytes

Abstract

This paper reports the effect of tyrothricin and tyrocidine hydrochloride upon exudative rabbit polymorphonuclear leucocytes and upon their phagocytic action in vitro. In high concentrations these substances caused cytoplasmic and nuclear disintegration; in lower concentrations altered staining reactions were observed. When there was no apparent microscopic injury to the cells, phagocytosis of pneumococci occurred as expected. It was also found that the presence of serum afforded some protection for the cells from the effects of these substances.

Dilutions of tyrothricin and tyrocidine hydrochloride were mixed with constant amounts of suspensions of a Type I mucoid strain of pneumococcus and of rabbit leucocytes, which were obtained according to the method of Mudd and his coworkers. 1 The tyrothricin used was obtained from a culture, “B.G.”, received from Dubos and prepared according to directions accompanying the culture. 2 . The purified tyrocidine hydrochloride was supplied by Dr. W. F. Verway of Sharp and Dohme, Inc. These mixtures were shaken for 10 min at 37°C in the Boerner-Mudd apparatus3 and smears were made, which were stained by a special phagocytic stain. 4 Suitable control experiments were conducted which showed that the media in which the tyrothricin was dissolved had no effect in the dilutions considered.

Table I shows the actions of tyrothricin and tyrocidine hydrochloride on leucocytes in the presence and absence of serum. This finding is typical of the results obtained in 20 instances.

Table II shows the effect of tyrothricin and tyrocidine hydrochloride upon the amount of phagocytosis taking place, recorded as the percentage of leucocytes containing pneumococci when 50 cells were observed, and also upon the pneumococci themselves, expressed by the amount of lysis occurring.

When normal leucocytes in saline suspension are treated with the phagocytic stain employed, the nuclei are stained red and the cytoplasm a purplish blue.