Tracheal versus pulmonary deposition and clearance of inhaled Pasteurella haemolytica or Staphylococcus aureus in mice

The aim of this investigation was to do a comparative study on the deposition and clearance of inhaled bacteria between the lungs and tracheae of mice exposed to aerosols of bacteria. Mice were divided into 4 groups of 72 each and exposed to aerosols of P. haemolytica or S. aureus in 4 replicates. The numbers of bacteria were determined in the trachea and lungs of mice sacrificed 0, 2, 4, 8 12, 24, 48 and 72 h postexposure. Results indicated that bacterial deposition was greater in lungs than in tracheae. No significant (P > 0.05) difference was observed between P. haemolytica and S. aureus clearance rates. Although bacteria were rapidly eliminated from the whole respiratory tract, bacterial clearance was significantly (P < 0.002) faster in tracheae than lungs. A significant (P < 0.05) replicate effect was also observed.