A Low-Molecular-Weight Alginate Oligosaccharide Disrupts Pseudomonal Microcolony Formation and Enhances Antibiotic Effectiveness

Abstract

In chronic respiratory disease, the formation of dense, 3-dimensional "microcolonies" by Pseudomonas aeruginosa within the airway plays an important role in contributing to resistance to treatment. An in vitro biofilm model of pseudomonal microcolony formation using artificial-sputum (AS) medium was established to study the effects of low-molecular-weight alginate oligomers (OligoG CF-5/20) on pseudomonal growth, microcolony formation, and the efficacy of colistin. The studies employed clinical cystic fibrosis (CF) isolates (n ϭ 3) and reference nonmucoid and mucoid multidrug-resistant (MDR) CF isolates (n ϭ 7). Bacterial growth and biofilm development and disruption were studied using cell viability assays and image analysis with scanning electron and confocal laser scanning microscopy. Pseudomonal growth in AS medium was associated with increased ATP production (P Ͻ 0.05) and the formation (at 48 h) of discrete (Ͼ10-m) microcolonies. In conventional growth medium, colistin retained an ability to inhibit growth of planktonic bacteria, although the MIC was increased (0.1 to 0.4 g/ml) in AS medium compared to Mueller-Hinton (MH) medium. In contrast, in an established-biofilm model in AS medium, the efficacy of colistin was decreased. OligoG CF-5/20 (Ն2%) treatment, however, induced dose-dependent biofilm disruption (P Ͻ 0.05) and led to colistin retaining its antimicrobial activity (P Ͻ 0.05). While circular dichroism indicated that OligoG CF-5/20 did not change the orientation of the alginate carboxyl groups, mass spectrometry demonstrated that the oligomers induced dose-dependent (Ͼ0.2%; P Ͻ 0.05) reductions in pseudomonal quorum-sensing signaling. These findings reinforce the potential clinical significance of microcolony formation in the CF lung and highlight a novel approach to treat MDR pseudomonal infections.

Seaweeds as nutraceuticals for health and nutrition

“…OligoG is an edible alginate oligosaccharide derivative which has already been shown in vitro to disrupt P. aeruginosa biofilms. Pritchard et al (2017) used artificial sputum medium with clinical cystic fibrosis isolates to measure the effect of OligoG on a model, multidrug-resistant pseudomonal biofilm, and also evaluated whether OligoG (CF-5/20) could reduce the dose of drugs normally required to treat infections. The antibiotic Colistin was used as a pharmaceutical standard in combination with the seaweed derivative.…”

Single-cell RNA sequencing analysis reveals alginate oligosaccharides preventing chemotherapy-induced mucositis

“…6,10 Alginate oligosaccharides (AOS) are excellent natural products derived from the degradation of alginate. They are attracting great attention from a pharmaceutical perspective [15][16][17] because of their following benefits: anti-inflammatory, 16 anti-apoptosis, 18 antiproliferation, 19 antioxidant activities, 15,18,20 and even anti-cancer properties. 21 AOS benefits intestinal morphology and barrier function by increasing the length of intestinal villi, the content of secretory immunoglobulin A, and the number of Goblet cells.…”

A glycopolymer improves vascoelasticity and mucociliary transport of abnormal cystic fibrosis mucus

“…Although initial clinical trials with OligoG were not definitive in patients with CF (54), interacting with pathologic CF mucins directly via PAAG may have inherent advantages as compared with indirectly addressing this by depleting free Ca 2+ , since the concentrations of chelating agents required to induce such effects are high (13); this could conceivably precipitate adverse effects, disrupt epithelial integrity (55), and diminish Clsecretion (56). Noting that biofilm extracellular biopolymer substances exhibit polyanionic structure and electrostatic properties similar to those of mucins (57), and low-WM Ca 2+ chelators disrupt biofilms (58,59), bacterial biofilms may also be a potential target for PAAG.…”