Overcoming drug resistance with alginate oligosaccharides able to potentiate the action of selected antibiotics

The uncontrolled, often inappropriate use of antibiotics has resulted in the increasing prevalence of antibiotic-resistant pathogens, with major cost implications for both US and European healthcare systems. We describe the utilization of a low molecular weight oligosaccharide nanomedicine (OligoG) based on the biopolymer alginate, which is able to perturb multi-drug resistant (MDR) bacteria by modulating biofilm formation/persistence and reducing resistance to antibiotic treatment; evident using conventional and robotic MIC screening and microscopic analyses of biofilm structure. OligoG increased the efficacy of conventional antibiotics (up to 512-fold) against important MDR pathogens including Pseudomonas, Acinetobacter and Burkholderia spp., appearing to be effective with several classes of antibiotic (i.e. macrolides, β-lactams, tetracyclines). Using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) increasing concentrations of alginate oligomer (2, 6 and 10%) were shown have a direct effect on the quality of the biofilms produced and on the health of the cells within that biofilm. Biofilm growth was visibly weakened in the presence of 10% OligoG as seen by decreased biomass and increased intercellular spaces, with the bacterial cells themselves becoming distorted and uneven due to apparently damaged cell membranes. This study demonstrates the feasibility of reducing the tolerance of wound biofilms to antibiotics with the use of specific alginate preparations

Roles of Three Transporters, CbcXWV, BetT1, and BetT3, in Pseudomonas aeruginosa Choline Uptake for Catabolism ▿ †

Pseudomonas aeruginosa uses the quaternary amine choline as a carbon source, osmoprotectant, and macromolecular precursor. The importance of choline in P. aeruginosa physiology is highlighted by the presence of multiple known and putative choline transporters encoded within its genome. This report describes the relative roles of three choline transporters, the ABC transporter CbcXWV and two symporters, BetT1 and BetT3, in P. aeruginosa growth on choline under osmotic conditions that are physiologically relevant to eukaryotic hosts. The increased lag phases exhibited by the ΔbetT1 and ΔbetT1 ΔbetT3 mutants relative to the wild type upon transfer to medium with choline as a sole carbon source suggested roles for BetT1 and BetT3 in cells newly exposed to choline. BetT3 and CbcXWV, but not BetT1, were sufficient to support growth on choline. betT1 and betT3 expression was regulated by the repressor BetI and choline, whereas cbcXWV expression was induced by the activator GbdR and glycine betaine. The data support a model in which, upon transfer to a choline-based medium, the glycine betaine derived from choline taken up by BetT1 and BetT3 promotes subsequent GbdR-mediated cbcXWV induction. Furthermore, growth data indicated that the relative contributions of each transporter varied under different conditions, as BetT1 and CbcXWV were the primary choline transporters under hypo-osmolar conditions whereas BetT3 was the major choline transporter under hyperosmolar conditions. This work represents the first systematic approach to unravel the mechanisms of choline uptake in P. aeruginosa, which has the most complex bacterial choline uptake systems characterized to date