Inhibition of the AdeABC efflux pump reverts levofloxacin resistance in uropathogenic Acinetobacter baumannii

Uropathogenic multidrug-resistant Acinetobacter baumannii confers resistance to antimicrobials by its potential virulence mechanism called the Efflux pump system. Resistance-Nodulation-Division transporter (RND), AdeABC, involves fluoroquinolones as its substrate, thereby limiting the clinical efficacy of levofloxacin in treating nosocomial infectious agents. Highly regarded synthetic efflux pump inhibitors (EPI) display cytotoxicity and nephrotoxicity, making them not applicable for clinical practice. High-throughput virtual screening (HTVS) of pyrrole ring-based RND inhibitor phytochemicals against the AdeB (transmembrane domain) and piperine, which was identified as the lead phytochemical molecule. This study exploits piperine (alkaloid) as an efflux pump inhibitor, and its efficacy is compared with that of a synthetic efflux pump inhibitor, which renders reduced mammalian cytotoxicity when studied in Escherichia coli and Pseudomonas aeruginosa. Co-administration of piperine with levofloxacin inhibits the efflux pump and reduces bacterial growth by 18.68%, thereby restoring the levofloxacin susceptibility of the bacterial strain. Furthermore, Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) analysis of the bacterial strain yielded disruption of the biofilm matrix as the RND efflux transporter function is halted by Synthetic EPI and piperine, as efflux inhibitors. It is noteworthy that both the lead molecules exhibited reduced cytotoxicity when tested with the mammalian HEK cell lines, making them potent EPI candidates.