Mode of nitric oxide delivery affects antibacterial action

Nitric oxide (NO) is a broad-spectrum antibacterial agent, making it an attractive alternative to traditional antibiotics for treating infections. To date, a direct comparison of the antibacterial activity of gaseous NO (gNO) versus water-soluble NO-releasing biopolymers has not been reported. In this study, the bactericidal action of NO-releasing chitosan oligosaccharides was compared to gNO treatment against cystic fibrosis-relevant Gram-positive and Gram-negative bacteria. A NO exposure chamber was constructed to enable the dosing of bacteria with gNO at concentrations up to 800 ppm under both aerobic and anaerobic conditions. Bacteria viability, solution properties (i.e., pH, NO concentration), and toxicity to mammalian cells were monitored to ensure a thorough understanding of bactericidal action and reproducibility for each delivery method. The NO-releasing chitosan oligosaccharides required significantly lower NO doses relative to gNO therapy to elicit antibacterial action against Pseudomonas aeruginosa and Staphylococcus aureus under both aerobic and anaerobic conditions. Reduced NO doses required for bacteria eradication using water-soluble NO-releasing chitosan were attributed to the release of NO in solution, removing the need to transfer from gas to liquid phase and the associated long diffusion distances of gNO treatment.