Deciphering the action of polymyxins on pentose phosphate pathway metabolism in Acinetobacter Baumannii: a metabolite-based target towards safe antibiotic treatment

Emergence of Acinetobacter baumannii as multidrug-resistant (MDR) bacteria are a major global threat to the healthcare system, forcing the classic polymyxins to be revisited as the last-line therapy against MDR Gram-negative bacteria including A. baumannii. It exhibits rapid bactericidal activity through ‘self-uptake’ pathway to induce local membrane disturbance, osmotic imbalance which lead to cell death. Nevertheless, polymyxins are limited due to the previously reported nephrotoxicity and ineffective suboptimal concentrations among patients. Bacterial metabolic reaction toward antibiotics has not been well studied with cutting-edge metabolomics. Understanding the metabolome of bacterial cells can potentially open an opportunity for novel effective antibacterial therapy. Previous study indicated that there were significant global metabolic disturbance of A. baumannii induced by polymyxin treatments including D-ribose-5-phosphate, D-erythrose-4-phosphate and D- sedoheptulose-7-phosphate of pentose phosphate pathway (PPP) metabolites, highlighting the potential polymyxin target. Therefore, this study aims to investigate the mechanism of polymyxins action on the PPP metabolism in A. baumannii, employing a targeted metabolomics approach through in vitro static time-kill method and metabolic pathway analysis across different time points at 1 hour and 4 hours. Polymyxin B (2mg/L) induced significant bactericidal effect in A. baumannii as rapid killing was observed after 1 hour treatment. However, the bactericidal activity decreased after the first hour as the bacterial growth significantly increased at 4 hours. The significant bactericidal effect of polymyxin at 1 hour reflects its potential in treating A. baumannii infection and further analyzed through metabolomics study. Through targeted metabolomics, detailed analysis on polymyxins’ activity against A. baumannii at cellular level, specifically for PPP metabolism able to provide a novel insight for alternative strategy in combating MDR bacterial infection