OligoG CF-5/20 Disruption of Mucoid Pseudomonas aeruginosa Biofilm in a Murine Lung Infection Model

Abstract

Biofilm growth is a universal survival strategy for bacteria, providing an effective and resilient approach for survival in an otherwise hostile environment. In the context of an infection, a biofilm provides resistance and tolerance to host immune defenses and antibiotics, allowing the biofilm population to survive and thrive under conditions that would destroy their planktonic counterparts. Therefore, the disruption of the biofilm is a key step in eradicating persistent bacterial infections, as seen in many types of chronic disease. In these studies, we used both in vitro minimum biofilm eradication concentration (MBEC) assays and an in vivo model of chronic biofilm infection to demonstrate the biofilm-disrupting effects of an alginate oligomer, OligoG CF-5/20. Biofilm infections were established in mice by tracheal instillation of a mucoid clinical isolate of Pseudomonas aeruginosa embedded in alginate polymer beads. The disruption of the biofilm by OligoG CF-5/20 was observed in a dose-dependent manner over 24 h, with up to a 2.5-log reduction in CFU in the infected mouse lungs. Furthermore, in vitro assays showed that 5% OligoG CF-5/20 significantly reduced the MBEC for colistin from 512 g/ml to 4 g/ml after 8 h. These findings support the potential for OligoG CF-5/20 as a biofilm disruption agent which may have clinical value in reducing the microbial burden in chronic biofilm infections. It has been suggested that biofilms are present in more than 65% of all bacterial infections (1). Biofilm-associated bacteria show an innate resistance to antibiotics, disinfectants, and host defense mechanisms (2, 3) and are thought to contribute to survival in chronic lung infections. Several in vitro studies have demonstrated that bacteria growing in a biofilm can become 10 to 1,000 times more resistant to the effects of antimicrobial agents than planktonic-growing bacteria of the same strain (4, 5). Patients with cystic fibrosis (CF) are highly susceptible to lung infections. As the disease progresses their lungs become chronically infected by P. aeruginosa as a biofilm infection (6), contributing to the destructive cycle of inflammation and fibrosis (7). Clinically, the presence of mucoid variants is associated with poor prognosis, deterioration of lung function, and increased tissue damage (2, 8). Therefore, the disruption of the biofilm is a key step in eradicating persistent bacterial infections, as is seen in many types of chronic disease.The novel alginate oligomer OligoG CF-5/20 is a low-molecular-weight oligosaccharide enriched from sodium alginate polysaccharides. It is an oligomer composed of ␣-L-guluronic acid (Ͼ85%) and ␤-D-mannuronic acid (Ͻ15%) (Fig. 1). OligoG CF-5/20 is currently in phase 2b clinical trials in CF patients. Previous in vitro studies have shown the ability of OligoG CF-5/20 to perturb biofilm formation, thereby reducing tolerance to antibiotic treatment (9-12).High-molecular-weight polymeric alginate is one of the components produced by P. aeruginosa in the formation of biofilms in the a...

Antibiotic treatment of biofilm infections

“…Another biofilm tolerance mechanism that can be targeted is the matrix, which reduces the effect of antibiotics and the immune system on biofilm bacteria. We have recently shown in an animal model of chronic lung infection that OligoG (AlgiPharma, Sandvika, Norway), an oligomer of alginate which destabilizes the alginate matrix, improves the effect of the immune system and antibiotics on P. aeruginosa biofilm supporting previous studies showing the anti‐biofilm effect of OligoG . OligoG is developed as a dry powder for inhalation (DPI), and a solution for nebulization, as an orphan drug product for treating CF patients.…”

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

“…The observed lowering of the efficacy of colistin in AS medium, therefore, may not only be related to an altered growth rate in this environment (which mimics growth conditions in the CF lung), but also may be due to LPS modification and/or direct binding by mucin in the AS medium, effectively sequestering free antibiotic (41). This EPS effect, and the apparent differences in MICs for colistin-treated NH57388A (with MIC values 4 times greater in AS than in MH medium) reflect the 10 4 -fold difference previously observed between MIC (0.094 g/ml) and MBEC (Ͼ512 g/ml) values for NH57388A in vitro (32).…”

“…has previously been attributed to irreversible binding at the bacterial cell surface (30). Moreover, the ability of OligoG CF-5/20 to potentiate the effectiveness of colistin against mucoid NH57388A biofilms has recently been demonstrated in MBEC assays (32). In this model, the ability of OligoG CF-5/20 (both alone and more markedly with colistin) to effectively disrupt the EPS of established biofilms was clearly evident.…”

“…1D). Treatment for 1 h with colistin alone at 0.5ϫ the minimum biofilm eradication concentration (MBEC), as previously described (32), was associated with decreased density of the resultant biofilm (Fig. 1E).…”

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.…”