In vivo activity of proteases of Pseudomonas aeruginosa in a rat model.

The granuloma pouch technique was used to study the in vivo characteristics of four strains of Pseudomonas aeruginosa that differed in levels of alkaline protease and elastase production. Bacterial counts, alkaline protease and elastase concentrations, and IgG levels of pouch exudates were determined quantitatively; total protein levels were determined semiquantitatively. In vivo protease concentrations were in the nanogram range; during the investigated period individual strains either increased enzyme production or remained negative. In vitro alkaline protease:elastase ratios correlated with in vivo ratios in three of the four strains. Proteolytic strains caused a decrease in IgG and alpha 2-fraction proteins. Purified rat IgG was cleaved rapidly by elastase and slowly by alkaline protease; both cleaved IgG at the hinge region. The study determines the concentration of P aeruginosa alkaline protease and elastase after infection in a rat model, shows cleavage of rat IgG and other proteins due to alkaline protease and elastase, and suggests that enzymes other than proteases are involved in the pathogenesis of P aeruginosa infections.