Chronic pulmonary infections with Pseudomonas aeruginosa remain a serious problem in patients with cystic fibrosis. Structurally altered lung mucosa and local inflammation may impair bacterial clearance from the airways. This hypothesis was investigated in (1) the reserpinized rat, (2) proteinase-pretreated rat lungs, and (3) Type III hypersensitivity rat lung models. Reserpine treatment led to surface alterations of Type I epithelial lung cells and diminished food uptake. Significantly enhanced P. aeruginosa colony-forming units (CFU) were found in all (12 of 12) rat lungs 48 h after challenge compared to partially starved rats (p less than 0.025) or untreated rats (p less than 10(-6)). Pretreatment of normal rat lungs with elastase from polymorphonuclear leukocytes (PMN-elastase) resulted in extensive tissue damage, and 48 h after bacterial challenge the mean P. aeruginosa CFU of 12 animals was significantly higher 1.1 X 10(4) +/- 1.0 X 10(4) CFU; p less than 0.01) than in the reserpinized rat lungs. P. aeruginosa organisms were also found in PMN-elastase-treated rat lungs not challenged with bacteria (five of 12 animals), suggesting cross infection from infected animals in the same cage. In immunized rats that were challenged with aerosolized antigen (bovine serum albumin) and P. aeruginosa, bacterial CFU after 10 h were significantly higher than in nonimmune animals (p less than 0.005), and highest after 48 h when P. aeruginosa alkaline proteinase was used as the antigen (1.2 X 10(5) +/- 1.4 X 10(5) CFU). These data provide new evidence that clearance of P. aeruginosa from lung tissue is impaired after malnutrition, epithelial cell alteration, or epithelial cell damage.(ABSTRACT TRUNCATED AT 250 WORDS)