Intracellular <i>Pseudomonas aeruginosa</i> within the Airway Epithelium of Cystic Fibrosis Lung Tissues.

Abstract

<b>Rationale:</b> <i>Pseudomonas aeruginosa</i> is the major bacterial pathogen colonizing the airways of adult patients with cystic fibrosis (CF) and causes chronic infections that persist despite antibiotic therapy. Intracellular bacteria may represent an unrecognized reservoir of bacteria that evade the immune system and antibiotic therapy. Although the ability of <i>P. aeruginosa</i> to invade and survive within epithelial cells has been described <i>in vitro</i> in different epithelial cell models, evidence of this intracellular lifestyle in human lung tissues is currently lacking. <b>Objectives:</b> To detect and characterize intracellular <i>P. aeruginosa</i> in CF airway epithelium from human lung explant tissues. <b>Methods:</b> We sampled lung explant tissues from patients with CF undergoing lung transplantation and non-CF lung donor control tissue. We analyzed lung tissue sections for the presence of intracellular <i>P. aeruginosa</i> using quantitative culture and microscopy, in parallel to histopathology and airway morphometry. <b>Measurements and Main Results:</b> <i>P. aeruginosa</i> was isolated from the lungs of seven patients with CF undergoing lung transplantation. Microscopic assessment revealed the presence of intracellular <i>P. aeruginosa</i> within airway epithelial cells in three of the seven patients analyzed at a varying but low frequency. We observed those events occurring in lung regions with high bacterial burden. <b>Conclusions:</b> This is the first study describing the presence of intracellular <i>P. aeruginosa</i> in CF lung tissues. Although intracellular <i>P. aeruginosa</i> in airway epithelial cells is likely relatively rare, our findings highlight the plausible occurrence of this intracellular bacterial reservoir in chronic CF infections.