Suppression of virulence factors of pseudomonas aeruginosa by subinhibitory concentrations of quaternary ammonium salts.

The effect of subinhibitory concentrations (sub-MICs) of two homologous series of "soft" quaternary ammonium salts (QATs) upon the expression of phospholipase C (Pseudomonas aeruginosa strain 72/92), elastase, proteinase and permeability activity (P. aeruginosa 9/92) was studied. Both strains were isolated from the patients suffering from nosocomial infections. Phospholipase C was the most markedly inhibited enzyme. The inhibitory effect was directly proportional to the concentration of substances but the degree of inhibition in the two homologous series was different. In the second strain of P. aeruginosa its production of elastase, permeability factor and mainly its proteinase activity were less affected by the series of tested QATs. A significant inhibition of production of these factors was manifested only in higher concentrations particularly by the substances with longer alkyls. The effect of QATs on the production of virulence factors could be attributed to their influence on the metabolic activity of organisms.