Botanicals from Aframomum letestuanum Gagnep. (Zingiberaceae) can overcome the multidrug resistance of Klebsiella species overexpressing AcrAB-TolC efflux pumps

Abstract

Background: Bacteria belonging to the genus Klebsiella have developed resistance mechanisms to clinically used antibiotics, leading to their loss of efficacy. In the present study, the in vitro antibacterial activity of methanol extracts from Aframomum letestuanum, as well as their modes of action against a panel of 14 bacterial species belonging to the genus Klebsiella including multidrug-resistant (MDR) phenotypes overexpressing efflux pumps were evaluated.

Methods: The broth microdilution method was used to assess the antibacterial activities of plant extracts (botanicals), while standard experimental protocols were used to study modes of action. Harborne's qualitative reference methods were used to identify the major groups of secondary metabolites present in the botanicals.

Results: Phytochemical screenings revealed that botanicals contain alkaloids, terpenoids, phenols, flavonoids, tannins, saponins, and anthocyanins. Botanicals from A. letestuanum seed pulp and seed inhibited the growth of all the bacteria tested, with MICs ranging from 16 to 512 μg/mL (pulp) and 64 to 2048 μg/mL (seed). The pulp extract had excellent activity, with MIC values of 16 μg/mL against K2, 32 μg/mL against Kp 80, and Kp 126, and 64 μg/mL against Kp55, Kp63, and ATCC11296. The seed extract displayed a MIC of 64 μg/mL against Kp58 and Kp2. A. letestuanum seed pulp extract inhibited bacterial growth in the exponential phase and induced inhibition of H⁺-ATPase-dependent proton pumps in K. pneumoniae ATCC11296.

Conclusion: Botanicals from A. letestuanum are potential phytomedicines that deserve further investigation to develop novel drugs to overcome the multidrug resistance of Klebsiella species.