AI Summary
The study aimed to find an efflux inhibitor for colistin to combat multi-drug resistant pathogens. Through various tests, argatroban was identified as a potential efflux inhibitor and showed synergy with colistin against resistant bacteria.
The growing multi-drug resistant (MDR) among ESKAPE pathogens is a huge challenge. Increased resistance to last-resort antibiotics like colistin has further aggravated this. Efflux is identified as a major route of colistin–resistance. So, finding an FDA- approved efflux inhibitor for potential application as an adjuvant to colistin is the primary objective of this study. E. coli AcrB pump inhibitors and substrates were used to develop and validate the pharmacophoric model. Drugs confirming this pharmacophore were subjected to molecular docking to identify hits for AcrB binding pocket. The efflux inhibition potential of the top hit was validated through in vitro evaluation of MIC in combination with colistin. The Checkerboard assay was done to demonstrate synergism which was further corroborated by the Time-kill assay. Ten common pharmacophore hypotheses were successfully generated using substrate/inhibitors. Following enrichment analysis AHHNR.100 was identified as the top-ranked hypothesis, and 207 unique compounds were found to confirm to this hypothesis. Multi-step docking of these compounds against the AcrB protein revealed argatroban as the top non-antibiotic hit. This significantly inhibited the efflux activity of colistin-resistant clinical isolates K. pneumoniae (n=1) and M. morganii (n=2). Further, its combination with colistin enhanced the susceptibility of these isolates, and the effect was found to be synergistic. Accordingly, the time-kill assay of this combination showed 8 log and 2 log reductions against K. pneumoniae and M. morganii, respectively. In conclusion, this study found argatroban as a bacterial efflux inhibitor that can be potentially used to overcome efflux-mediated resistance.