The Effects of Antibiotics on Enterobacterial Lipopolysaccharides (Endotoxins), Hemagglutination and Hemolysis

A study on the effects of various antibiotics on enterobacterial lipopolysaccharides and hemagglutination and hemolysis revealed the following results: Small amounts of polymyxin B (1–1.25 μg/ml) and neomycin (12.5–15 μg/ml) and larger amounts of humycin (50–100 μg/ml) and streptomycin (40–125 μg/ml) inhibit enterobacterial hemagglutination and hemolysis if the antibiotics are added to highly purified lipopolysaccharide (5 μg/ml) prior to modification of sheep red blood cells. Somewhat larger amounts are required for inhibition with less highly purified lipopolysaccharides and crude preparations.Bacitracin (2500 μg/ml), penicillin (1000 μg/ml), erythromycin (1000 μg/ml), and novobiocin (500 μg/ml) have no such effect.Polymyxin B, neomycin, humycin, and streptomycin do not inhibit hemagglutination and hemolysis of previously modified red blood cells.Treatment of red blood cells with the antibiotics prior to modification does not prevent hemagglutination and hemolysis by homologous bacterial antibody and complement.Treatment of human red blood cells of blood group A with mixtures of antibiotics (polymyxin B or neomycin), S. sonnei lipopolysaccharide, and S. sonnei antibodies of human origin does not inhibit hemagglutination by blood group A antiserum, indicating that the red blood cells had not become inagglutinable. Coombs antiserum does not cause hemagglutination of these treated red blood cells.Polymyxin B, neomycin, humycin, and streptomycin do not abolish antibody neutralizing capacity of enterobacterial lipopolysaccharides in hemolysis inhibition tests, although a slight degree of inhibition was found.It is tentatively concluded that polymyxin B, neomycin, humycin, and streptomycin interfere with the attachment of lipopolysaccharides to the surface of red blood cells and, to a lesser degree, cause alteration of their antibody reacting capacity.The significance of the results is discussed with particular reference to the possible specificity of the action of antibiotics on enterobacterial lipopolysaccharides and the bearing of the findings on the mode of action of the antibiotics.