Comparison of the immunological response in mice after bronchoscopic and surgical methods for delivery of Pseudomonas aeruginosa to murine airways.

We have established improved methods to access the mouse airways and lungs for pulmonary research. We have applied a non-surgical, bronchoscopic system with a camera to bacterial infection studies and found it reduced mortality and weight change in infected mice compared to our previously used procedure, a tracheostomy involving surgery. The two procedures were compared with and without bacteria to identify the inflammatory responses to the surgery and to the bacteria involved. We found the mouse tolerated the bronchoscope much better than the tracheostomy which allowed delineation of the effects of the bacteria from those of the surgical wound. The bronchoscope appeared to reduce stress to the mice, compared to the tracheostomy, and provided a significant benefit of reducing morbidity and mortality, thus reducing the number of mice needed for experiments. We found that mice receiving sterile beads instilled in the lung by tracheostomy lost more weight compared to mice undergoing bronchoscopy. Adding bacteria gave rise to even greater weight loss displaying significantly higher in surgery compared to bronchoscopy groups. Furthermore for surgery, immune cells (especially neutrophils) were increased in broncho-alveolar lavage fluid, as were pro-inflammatory cytokines TNF-α, IL-1β, and IL-6. The effects from the surgical wound are significant and should be recognized and incorporated into experimental designs to best reflect the condition the mouse is intended to model.