Acid aspiration provokes the pneumonia caused by multidrug-resistant Acinetobacter baumannii in BALB/c mice

SummaryObjectiveTo determine whether acid aspiration provokes the development of multidrug-resistant Acinetobacter baumannii (MDRAB) pneumonia in its host.MethodsGroups of mice were inoculated intratracheally (IT) with 50 μl of 0.1 N HCl and 1 × 108 colony-forming units (CFU) Ab396 (A + Ab group), or 50 μl of 0.1 N HCl and 20 μl of 0.9% saline (A + S group), or 20 μl of 0.9% saline and 1 × 108 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.ResultsOnly 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.ConclusionsLung 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.