Abstract
The bulbs of Allium species are a known source of antibacterial phytochemicals. Anti-infective, efflux pump and biofilm inhibitory activities of bulb extracts of selected Ghanaian shallots Allium cepa var aggregatum were evaluated using the HT-SPOTi assay and other whole-cell phenotypic screening techniques to determine their possible mechanisms of action. Ethanol and aqueous extracts of white A. cepa inhibited the growth of Mycobacterium smegmatis mc(2) 155 and Escherichia coli, respectively. The majority of the Allium extracts significantly (p < 0.05) exhibited efflux pump inhibitory activity against all the acid-fast, Gram-positive and Gram-negative strains used. Hexane and chloroform extract of the pink A. cepa and the aqueous extract of the white A. cepa significantly inhibited M. smegmatis biofilm formation. For Pseudomonas aeruginosa, the inhibition was observed at 250 µg/mL for the aqueous extract (~77.34%) and 125 µg/mL for the hexane extract (~76.51%). The results suggest that Ghanaian shallots could potentially be useful when further developed to tackle antimicrobial resistance, particularly in tuberculosis (TB).