The effect of leukocyte hydrolases on bacteria : VII. Bactericidal and bacteriolytic reactions mediated by leukocyte and tissue extracts and their modifications by polyelectrolytes.

Crude extracts of human blood leukocytes were employed as a source of bactericidal and bacteriolytic agents againstStaphylococcus aureus. While the bactericidal action of the extracts was a very rapid process, bacteriolysis is a very slow process. Both the killing and the lysis of staphylococci depended on the age of the culture, maximal effects being obtained only with young cells. The killing of staphylococci by the extracts was absolutely dependent on the density of bacteria employed. On the other hand, bacteriolysis was only very slightly affected when large numbers of bacteria were employed. Both the bactericidal and bacteriolytic reactions were optimal at pH 5.0. Under similar conditions, extracts of pus and the "cocktail" of enzymes were both bactericidal and bacteriolytic, but extracts of small intestine and of platelets were not significantly bactericidal. Experiments, designed to differentiate between the bactericidal and bacteriolytic properties of the extracts showed that both properties were preserved following heating in acid solutions but were completely destroyed following heating in alkaline solutions. The bactericidal factor in the lysates could be readily adsorbed on large numbers of viableStaph. aureus andE. coli, but the bacteriolytic properties of the extracts could not be removed by adsorption. The bactericidal effect of the extracts could not be inhibited by a variety of anionic polyelectrolytes, but all these agents strongly inhibited the bacteriolytic effect. Moreover, several of the anionic substances potentiated the bactericidal effects mediated by the extracts. Potentiation of these effects was also caused by protamine sulfate and by polylysine, which were highly bactericidal by themselves. The only substance that was found to abolish the bactericidal effects of the extracts is ultracorten H. Historie and polylysine (which are highly bactericidal) lost their effects when mixed with certain concentrations of heparin or polyglutamic acid, which by themselves are not bactericidal, indicating that an appropriate balance between cationic and anionic substances may determine the bactericidal effects of cationic substances. Since the bactericidal properties of the lysates could not be abolished by any of the anionic macromolecular substances employed; it is suggested that the bactericidal agents present in crude whole lysates of leukocytes comprise a complex mixture of agents, some of which are not identical with cationic substances. Thus, the data suggest that the employment of highly purified cationic proteins of leukocytes and tissues to study bactericidal models may not reflect the actual conditions that prevail in inflammatory exudates. The possible role played by cationic and anionic polyelectrolytes in the control of bacterial survival and lysis in inflammatory exudates is discussed.