title: Untargeted metabolomics analysis reveals key pathways responsible for the synergistic killing of colistin and doripenem combination against Acinetobacter baumannii.
abstract: Combination therapy is deployed for the treatment of multidrug-resistant Acinetobacter baumannii, as it can rapidly develop resistance to current antibiotics. This is the first study to investigate the synergistic effect of colistin/doripenem combination on the metabolome of A. baumannii. The metabolite levels were measured using LC-MS following treatment with colistin (2 mg/L) or doripenem (25 mg/L) alone, and their combination at 15 min, 1 hr and 4 hr (n = 4). Colistin caused early (15 min and 1 hr) disruption of the bacterial outer membrane and cell wall, as demonstrated by perturbation of glycerophospholipids and fatty acids. Concentrations of peptidoglycan biosynthesis metabolites decreased at 4 hr by doripenem alone, reflecting its mechanism of action. The combination induced significant changes to more key metabolic pathways relative to either monotherapy. Down-regulation of cell wall biosynthesis (via D-sedoheptulose 7-phosphate) and nucleotide metabolism (via D-ribose 5-phosphate) was associated with perturbations in the pentose phosphate pathway induced initially by colistin (15 min and 1 hr) and later by doripenem (4 hr). We discovered that the combination synergistically killed A. baumannii via time-dependent inhibition of different key metabolic pathways. Our study highlights the significant potential of systems pharmacology in elucidating the mechanism of synergy and optimizing antibiotic pharmacokinetics/pharmacodynamics.
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, 3052, Australia.
authors.forename: Mohd Hafidz Mahamad
authors.initials: MH
authors.lastname: Maifiah
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, 3052, Australia.
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Creek
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, 3052, Australia.
authors.forename: Roger L
authors.initials: RL
authors.lastname: Nation
authors.affiliation: UNC Eshelman School of Pharmacy, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7569, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Forrest
authors.affiliation: Department of Pharmacy Practice, University at Buffalo, Buffalo, NY, USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Tsuji
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, 3052, Australia.
authors.forename: Tony
authors.initials: T
authors.lastname: Velkov
authors.affiliation: Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, VIC 3800, Australia.
authors.forename: Jian
authors.initials: J
authors.lastname: Li
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000378:metabolism*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003091:Colistin / Q000494:pharmacology*; D000077726:Doripenem / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D004359:Drug Therapy, Combination; D008563:Membrane Lipids / Q000378:metabolism; D055432:Metabolomics; D015398:Signal Transduction
chemical_list: D000900:Anti-Bacterial Agents; D008563:Membrane Lipids; D000077726:Doripenem; D003091:Colistin