Related Experiment Video
Updated: Aug 20, 2026
Intratracheal Inoculation of Fischer 344 Rats with Francisella tularensis
Published on: September 30, 2017
Host response to intratracheally instilled bacteria in ventilated and nonventilated rats
Angela M Brackenbury1, Lynda A McCaig, Li-Juan Yao
1Department of Medicine, St. Joseph's Health Care Centre, London, Ontario, Canada.
Objective:
Pneumonia occurs in approximately 7% of hospitalized patients. Susceptibility to certain bacteria such as Pseudomonas aeruginosa increases in critically ill patients, particularly those requiring mechanical ventilation. Previous studies investigating this susceptibility have used injurious modes of ventilation. The objective of this study was to evaluate the host's response to intratracheal instillation of P. aeruginosa in the setting of noninjurious mechanical ventilation and compare this with normal, spontaneously breathing animals receiving bacteria.
Design:
Randomized, controlled in vivo animal study.
Setting:
Research laboratory at a university-affiliated institution.
Subjects:
Adult male Sprague-Dawley rats.
Interventions:
Rats were randomized into four groups: spontaneously breathing given saline, spontaneously breathing given bacteria, mechanically ventilated given saline, and mechanically ventilated given bacteria. The ventilation strategy used involved low stretch (tidal volume of 8 mL/kg) with a positive end-expiratory pressure of 5 cm H2O.
Measurements And Main Results:
Lung compliance, bacterial recovery, surfactant, total cells, and cytokine concentrations in the lung lavage were analyzed after 4 hrs. Results showed that neither ventilation nor bacteria alone altered lung function, although the combination of ventilation and Pseudomonas significantly decreased arterial oxygenation and lung compliance. Increases in lavage cell counts, cytokines, and surfactant were observed in both groups administered bacteria compared with animals given saline. However, there were no significant differences in bacterial recovery, cell counts, cytokines, and surfactant measurements in the groups given bacteria.
Conclusions:
These data suggest that bacterial instillation with low-stretch ventilation had a significant effect on lung function but did not alter the inflammatory response to a bacterial challenge over this time course compared with spontaneously breathing animals.
Insights
Mechanical ventilation with Pseudomonas aeruginosa significantly impaired lung function and oxygenation in rats. However, noninjurious ventilation did not increase the inflammatory response to bacterial challenge compared to spontaneous breathing.
Area of Science:
- Pulmonary Medicine
- Critical Care Medicine
- Infectious Diseases
Background:
- Hospital-acquired pneumonia affects ~7% of inpatients.
- Critically ill patients, especially those on mechanical ventilation, are susceptible to Pseudomonas aeruginosa infections.
- Previous studies used injurious ventilation; this study uses noninjurious ventilation.
Purpose of the Study:
- To investigate the host response to Pseudomonas aeruginosa with noninjurious mechanical ventilation.
- To compare this response to spontaneously breathing animals given the bacteria.
Main Methods:
- Adult male Sprague-Dawley rats were used in a randomized, controlled in vivo animal study.
- Rats were divided into four groups: spontaneous breathing (saline/bacteria) and mechanical ventilation (saline/bacteria).
- A low-stretch ventilation strategy (8 mL/kg tidal volume, 5 cm H2O PEEP) was employed.
Main Results:
- Mechanical ventilation combined with Pseudomonas aeruginosa significantly reduced arterial oxygenation and lung compliance.
- Neither ventilation nor bacteria alone altered lung function.
- Increased lavage cell counts, cytokines, and surfactant were seen in bacteria-exposed groups, but without significant differences between ventilation and spontaneous breathing groups for these measures.
Conclusions:
- Low-stretch mechanical ventilation combined with Pseudomonas aeruginosa instillation significantly impacted lung function.
- Noninjurious ventilation did not alter the inflammatory response to bacterial challenge over 4 hours compared to spontaneous breathing.
More Related Videos
09:17A Robust Pneumonia Model in Immunocompetent Rodents to Evaluate Antibacterial Efficacy against S. pneumoniae, H. influenzae, K. pneumoniae, P. aeruginosa or A. baumannii
Published on: January 2, 2017
08:00Intubation-mediated Intratracheal (IMIT) Instillation: A Noninvasive, Lung-specific Delivery System
Published on: November 17, 2014