Ethanol Extract From the Stem Bark of Adansonia digitata L. (Baobab) Displays Therapeutic Potential Against Klebsiella pneumoniae Infection.

Background Pulmonary infection induced by Klebsiella pneumoniae is becoming one of the leading causes of respiratory infection worldwide. In recent years, the emergence of hypervirulent and multi-drug-resistant K. pneumoniae has been strongly associated with pneumonia. This study aimed to evaluate the in vitro and in vivo antibacterial properties of Adansonia digitata L. (Malvaceae), a medicinal plant traditionally used in the treatment of respiratory tract infections. Methodology Plant extract was obtained by maceration in ethanol. Qualitative chemical analysis of this extract was performed using standard methods. The in vitro antibacterial activities of the extracts alone and their combinations with Augmentin were evaluated using the broth microdilution method through the determination of Minimum Inhibitory Concentrations (MIC). The mechanisms of antibacterial action of the A. digitata extract were evaluated by targeting bacterial ATPases/H+ proton pump function, growth kinetics, outer membrane permeability, dehydrogenase activity, and leakage of nucleic acids. The therapeutic effect of the extract was evaluated in vivo on rats infected through the nasal cavity with K. pneumoniae. Results The phytochemical analysis of the A. digitata stem bark extract showed that it contains flavonoids, phenols, sterols, triterpenes, tannins, alkaloids, anthocyanins, anthraquinones, and saponins. The ethanol extract from A. digitata displayed in vitro antibacterial activities with MIC values ranging from 64 to 1024 μg/mL. A. digitata extract also displayed indifference (1 < fractional inhibitory concentration index (FICI) ≤ 4), additive (0.5 < FICI ≤ 1), and synergistic (FICI ≤ 0.5) effects with Augmentin that varied according to the tested bacteria. The plant extract induced changes in the bacterial growth kinetics, permeability of bacterial membranes, leakage of nucleic acids, and the inhibition of the bacterial ATPases/H+ proton pumps. Moreover, A. digitata extract showed to be active in vivo at the doses 5.00 and 9.00 mg/kg on K. pneumoniae-infected rats. Conclusions The findings demonstrate the in vitro antibacterial activity of A. digitata and its therapeutic efficiency against pneumonia induced by K. pneumoniae. Hence, A. digitata can be used for the development of phytomedicines to treat respiratory tract infections, particularly those caused by the tested bacteria. So, further studies are warranted.