Clinical isolates of Pseudomonas aeruginosa from severely burned patients were analyzed with regard to their capacity to induce inflammatory-mediator release from rat mast cells or human granulocytes. The bacterial strains were characterized according to their cell-associated hemolysin activity as well as their secreted hemolysin and phospholipase C activities. P. aeruginosa expressing heat-labile hemolysin and phospholipase C induced histamine release from rat mast cells and leukotriene formation from human granulocytes, while bacterial strains expressing heat-stable hemolysin were potent releasers of histamine but did not lead to leukotriene formation. The mediator-inducing capacity was dependent on the growth characteristics of the bacterial strains. The purified glycolipid (heat-stable hemolysin) of P. aeruginosa was a potent inducer of histamine release but did not initiate leukotriene formation. Exotoxin A did not affect inflammatory-mediator release. P. aeruginosa with leukotriene-inducing capacity also enhanced omega oxidation of endogenous leukotriene B4, suggesting an additional inactivation of the chemotactic potential. Our data suggest that both hemolysins of P. aeruginosa contribute to the pathogenicity of P. aeruginosa by inducing and modulating inflammatory-mediator release from various cells.

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