Antimicrobial efficacy of quaternary bisammonium salts and the effect of their sub-MICs on Pseudomonas aeruginosa virulence factors.

Antipseudomonadal activity of homologous series of six quaternary bisammonium salts (QBAS) (4,7-dioxo-3,8-dioxadekan-1,1-[bis(alkyldimethyldiammonium dibromide)] as well as the effect of their subinhibitory concentrations (sub-MICs) on Pseudomonas aeruginosa virulence factors was studied. Antibacterial activity of QBAS increased up to a certain length of the chain and then decreased with further elongation. All the tested sub-MICs of QBAS caused a significant suppression of phospholipase C activity (to 0-41%). Elastase and proteinase activity were less efficiently reduced. A more effective decrease of these activities was only found after treatment with one-fourth of the MICs of the tested substances. QBAS caused only an erratic decrease of alginate production.