title: Real-time examination of aminoglycoside activity towards bacterial mimetic membranes using Quartz Crystal Microbalance with Dissipation monitoring (QCM-D).
abstract: The rapid increase in multi-drug resistant bacteria has resulted in previously discontinued treatments being revisited. Aminoglycosides are effective "old" antibacterial agents that fall within this category. Despite extensive usage and understanding of their intracellular targets, there is limited mechanistic knowledge regarding how aminoglycosides penetrate bacterial membranes. Thus, the activity of two well-known aminoglycosides, kanamycin A and neomycin B, towards a bacterial mimetic membrane (DMPC:DMPG (4:1)) was examined using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). The macroscopic effect of increasing the aminoglycoside concentration showed that kanamycin A exerts a threshold response, switching from binding to the membrane to disruption of the surface. Neomycin B, however, disrupted the membrane at all concentrations examined. At concentrations above the threshold value observed for kanamycin A, both aminoglycosides revealed similar mechanistic details. That is, they both inserted into the bacterial mimetic lipid bilayer, prior to disruption via loss of materials, presumably aminoglycoside-membrane composites. Depth profile analysis of this membrane interaction was achieved using the overtones of the quartz crystal sensor. The measured data is consistent with a two-stage process in which insertion of the aminoglycoside precedes the 'detergent-like' removal of membranes from the sensor. The results of this study contribute to the insight required for aminoglycosides to be reconsidered as active antimicrobial agents/co-agents by providing details of activity at the bacterial membrane. Kanamycin and neomycin still offer potential as antimicrobial therapeutics for the future and the QCM-D method illustrates great promise for screening new antibacterial or antiviral drug candidates.
authors.affiliation: School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Tanmaya
authors.initials: T
authors.lastname: Joshi
authors.affiliation: School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Zhi Xiang
authors.initials: ZX
authors.lastname: Voo
authors.affiliation: Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia.
authors.forename: Bim
authors.initials: B
authors.lastname: Graham
authors.affiliation: School of Chemistry, Monash University, Clayton, Victoria 3800, Australia. Electronic address: Leone.Spiccia@monash.edu.
authors.forename: Leone
authors.initials: L
authors.lastname: Spiccia
authors.affiliation: School of Chemistry, Monash University, Clayton, Victoria 3800, Australia. Electronic address: Lisa.Martin@monash.edu.
authors.forename: Lisandra L
authors.initials: LL
authors.lastname: Martin
mesh_terms: D000617:Aminoglycosides / Q000737:chemistry*; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D040761:Biomimetic Materials; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry; D005601:Framycetin / Q000737:chemistry*; D007612:Kanamycin / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008567:Membranes, Artificial; D015394:Molecular Structure; D010715:Phosphatidylglycerols / Q000737:chemistry; D058525:Quartz Crystal Microbalance Techniques; D013816:Thermodynamics
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D008051:Lipid Bilayers; D008567:Membranes, Artificial; D010715:Phosphatidylglycerols; D005601:Framycetin; D007612:Kanamycin; C002773:dimyristoylphosphatidylglycerol; D004134:Dimyristoylphosphatidylcholine
keywords: Aminoglycoside; Antibiotic; Molecular mechanism; Quartz crystal microbalance; Supported lipid bilayer