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

288 mice were divided into four groups and exposed to aerosols of P. haemolytica or S. aureus in four replicates. The numbers of bacteria were determined in the trachea and lungs of mice killed 0, 2, 4, 8, 12, 24, 48 and 72 hours after exposure. Bacterial deposition was greater in lungs than in trachea. Little 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 faster in trachea than lungs. A significant replicate effect was observed.