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Updated: May 13, 2026
Murine Oropharyngeal Aspiration Model of Ventilator-associated and Hospital-acquired Bacterial Pneumonia
Published on: June 28, 2018
Acid aspiration provokes the pneumonia caused by multidrug-resistant Acinetobacter baumannii in BALB/c mice
Shyh-Ren Chiang1, Hung-Jen Tang, Chung-Hua Chen
1Department of Internal Medicine, Chi Mei Medical Center, 901, Chung-Hwa Road, Yung-Kang Dist., Tainan City, Taiwan.
Objective:
To determine whether acid aspiration provokes the development of multidrug-resistant Acinetobacter baumannii (MDRAB) pneumonia in its host.
Methods:
Groups of mice were inoculated intratracheally (IT) with 50 μl of 0.1N HCl and 1 × 10(8) colony-forming units (CFU) Ab396 (A+Ab group), or 50 μl of 0.1N HCl and 20 μl of 0.9% saline (A+S group), or 20 μl of 0.9% saline and 1 × 10(8) CFU of Ab396 (S+Ab group), or 50 μl of 0.9% saline and 20 μl of 0.9% saline (S+S group). Cytokines, bacterial loads in the bronchoalveolar lavage fluid (BALF), lung permeability, histopathology of the lungs, and survival rates were evaluated.
Results:
Only the A+Ab mice developed extensive Ab396 pneumonia and had significantly elevated bacterial loads, increased lung leakage, and lower levels of tumor necrosis factor alpha (TNF-α) compared with the other three groups (p<0.05, Mann-Whitney U-test). Moreover, a strong synergistic effect (p<0.05, two-way analysis of variance) was observed between the acid induction and Ab396 infection, resulting in lung injury and an unfavorable survival outcome.
Conclusions:
Lung injury caused by acid aspiration provoked secondary MDRAB pneumonia; also synergistic effects between acid aspiration and Ab396 infection resulted in a detrimental outcome in the infected mice.
Insights
Acid aspiration triggers multidrug-resistant Acinetobacter baumannii (MDRAB) pneumonia. This lung injury and bacterial infection synergistically worsen outcomes in mice.
Area of Science:
- Pulmonary Medicine
- Infectious Diseases
- Critical Care
Background:
- Acid aspiration is a common complication in critically ill patients.
- Multidrug-resistant Acinetobacter baumannii (MDRAB) is a significant nosocomial pathogen.
Purpose of the Study:
- To investigate if acid aspiration can precipitate the development of MDRAB pneumonia.
- To explore the synergistic effects between acid aspiration and MDRAB infection on lung injury.
Main Methods:
- Mice were intratracheally inoculated with hydrochloric acid and/or MDRAB (Ab396 strain).
- Evaluated outcomes included bacterial load, lung permeability, cytokine levels (TNF-α), histopathology, and survival rates.
Main Results:
- Mice exposed to both acid and MDRAB developed severe pneumonia with higher bacterial loads and lung leakage.
- A significant synergistic effect was observed between acid aspiration and MDRAB infection, leading to increased lung injury.
- Lower levels of TNF-α were noted in the group with both acid and MDRAB exposure.
Conclusions:
- Acid aspiration can provoke secondary MDRAB pneumonia.
- The combination of acid aspiration and MDRAB infection results in a detrimental synergistic effect on lung injury and survival.
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