INTERACTION OF PSEUDOMONAS-AERUGINOSA WITH HUMAN RESPIRATORY MUCOSA IN-VITRO

Pseudomonas aeruginosa commonly infects the airways of patients with cystic fibrosis and bronchiectasis. It produces several toxins that slow ciliary beat, stimulate mucus production and damage epithelium. It adheres to epithelial cells, damaged mucosa (in animal models), and mucus. However, little is known of the interaction of P. aeruginosa with intact human respiratory mucosa We have studied the interactions of a nonmucoid clinical isolate of P. aeruginosa with adenoid tissue in a novel organ culture model with an air-mucosal interphase P. aeruginosa (5.9+/-0.9x10(6) colony-forming units (cfu)) was pipetted onto the organ culture surface, and incubated for 15 min, 1, 2, 4, 8, 12, 16, and 24 h, at 37 degrees C in 5% CO2 in a humidified atmosphere. Assessment has been made by transmission and scanning electron microscopy. Transmission electron microscopy (TEM) showed that uninfected organ cultures had normal ultrastructure. TEM of infected organ cultures at 8 h showed significant epithelial damage: 43.9+/-10% of cells extruding from the epithelial surface, 17.7+/-3% of cells with loss of cilia, 32.9+/-10.22 of cells with mitochondrial damage, and 11.6+/-3% of cells with cytoplasmic blebbing. P. aeruginosa only infrequently adhered to normal epithelium, but adhered to areas of epithelial damage and to basement membrane. Scanning electron microscopy (SEM) of organ cultures up to 2 h found P. aeruginosa only infrequently associated with mucus. SEM at 4 h revealed P. aeruginosa predominantly associated with mucus and extruded damaged epithelial cells, but also occasionally associated with cilia, and very occasionally with unciliated cells. SEM also revealed loss of epithelial tight junctions in P. aeruginosa infected organ cultures, and P. aeruginosa were frequently seen in the gaps between epithelial cells. An extracellular matrix, possibly of bacterial origin, was seen bridging the space between bacteria and cell surface. We conclude that P. aeruginosa infection of this organ culture caused tissue damage and that P. aeruginosa preferentially adhered to mucus, damaged epithelium and basement membrane.