Comparison of four hemolysin-producing organisms (Escherichia coli, Serratia marcescens, Aeromonas hydrophila, and Listeria monocytogenes) for release of inflammatory mediators from various cells.

We investigated the role of various hemolysin-producing strains (Escherichia coli, Serratia marcescens, Aeromonas hydrophila, and Listeria monocytogenes) in induction of inflammatory mediators, e.g., histamine release from rat mast cells as well as the chemiluminescence response and the release of lipoxygenase transformation products from human polymorphonuclear neutrophils. Our data show that the hemolysin-positive bacteria as well as the hemolysin-positive culture supernatants were active in inducing the chemiluminescence response, leukotriene (LTB4 and LTC4) release from human granulocytes, and histamine release from rat mast cells. The degree of leukotriene release was dependent on the hemolysin type and on the expression of hemolysin activity. The E. coli alpha-hemolysin and the aerolysin-producing A. hydrophila were the most potent stimuli whether washed bacteria or bacterial supernatant was used. Bacteria expressing the S. marcescens hemolysin and the listeriolysin were only poor inducers of leukotriene generation. In contrast to leukotriene generation, all hemolysin-positive strains induced nearly the same histamine release in a dose-dependent manner. Our data suggest a potent role for various hemolysins as virulence factors in inducing the release of inflammatory mediators.