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 μg/ml to 4 μg/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.

FIG 1

Structure of 1→4-α-l-guluronic acid (G) and 1→4-β-d-mannuronic acid (M); OligoG CF-5/20 has at least 85% of the monomer as G residues.

FIG 2

(a) Killing effect of 5% OligoG CF-5/20 combined with local 16×MIC aztreonam treatment on alginate bead biofilm and planktonic P. aeruginosa NH57388A in vivo. (b) Killing effect of 5% OligoG CF-5/20 combined with local 16×MIC colistin treatment on alginate bead biofilm and planktonic P. aeruginosa NH57388A in vivo. (c) Killing effect of 5% OligoG CF-5/20 combined with local 16×MIC tobramycin treatment on alginate bead biofilm and planktonic P. aeruginosa NH57388A in vivo.

FIG 3

Effect of 0%, 0.2%, 1%, and 5% OligoG CF-5/20 on alginate bead biofilm of P. aeruginosa NH57388A in vivo.

FIG 4

Sigmoidal E_max modeling for the effect of OligoG CF-5/20 on biofilms of P. aeruginosa NH57388A in vivo.

FIG 5

Representative histology of H&E- and alcian blue-stained sections of lung tissues from controls and OligoG CF-5/20-treated mice.

FIG 6

Macroscopic lung pathology of mouse. The biofilms of alginate beads of NH57388A were administered by the intratracheal route to the lower left lung either left untreated (A) or with 5% OligoG (50 mg/ml) treatment only (B), with local 5% OligoG treatment and 16×MIC aztreonam treatment (C), with local 5% OligoG and 16×MIC colistin treatment (D), and with local 5% OligoG and 16×MIC tobramycin treatment (E). Lungs were removed at 24 h after bacterial challenge.

FIG 7

IL-1α with 0%, 0.2%, 1%, and 5% OligoG CF-5/20 on biofilm infection of P. aeruginosa NH57388A in vivo.