Pseudomonas aeruginosa from patients with cystic fibrosis affects functionof pulmonary surfactant

Patients with cystic fibrosis are severely affected by an infection with Ps eudomonas aeruginosa, a microbe known to synthesize phospholipase C. This s tudy was designed to determine whether that enzyme would affect the functio n of pulmonary surfactant phospholipids. Mucoid and nonmucoid strains of P. aeruginosa, freshly obtained from patients with cystic fibrosis, were cult ured for 12 h on agar plates. The bacteria were suspended in saline solutio n and then pelleted by centrifugation. The supernatant was used to dilute t he surfactant preparation, calf lung surfactant extract, from 35 to 2 mg/mL . Surfactant function, before and after incubation, was examined with a cap illary surfactometer, an instrument specifically developed for an evaluatio n of the ability of surfactant to maintain patency of a narrow glass tube, simulating a terminal conducting airway. Phospholipid hydrolysis was also e valuated biochemically by determining the total content of phospholipids in surfactant before and after incubation. In five experiments, the lipids we re separated with thin-layer chromatography, and the phosphorus content was determined in the diacylphosphatidylcholine band before and after incubati on for 6, 24, and 48 h. Capillary openness and phospholipid concentration d ecreased as enzyme concentration and time of incubation increased (p < 0.00 01). Linear regression showed a significant correlation between time of cap illary openness and phospholipid concentration (r = 0.957; p < 0.0001). Cal f lung surfactant extract hydrolysis was catalyzed by extracts of the bacte ria, particularly the nonmucoid, analogous to the catalysis observed with p hospholipase C. Surfactant hydrolysis catalyzed by enzymes from P. aerugino sa might severely affect surfactant function provided enzyme concentration is high and time of incubation is long.