Investigation of the susceptibility of clinical infection loads to nitric oxide antibacterial treatment

The persistent infection of medical devices by opportunistic pathogens has led to the development of antimicrobial medical device polymers. Nitric oxide (NO) is an endogenous antimicrobial molecule that is released through the degradation of synthetic donor molecules such as S-nitroso-N-acetylpenicillamine (SNAP) embedded into polymer membranes. It is hypothesized that the clinical success of these polymers is enhanced by the physiological release of NO and the consequent prevention of infection. However, such NO-releasing materials have never been evaluated against microbial loads that are commensurate with clinical infection levels. This study aimed to develop a standardized polymer film impregnated with SNAP that consistently releases NO and evaluates its efficacy against bacterial loads that represent clinical infection parameters. Microbial loads of 10³, 10⁵, and 10⁸ (colony-forming units) CFU mL⁻¹ were exposed to the NO-releasing polymer, corresponding to bloodstream infections, catheter-associated urinary tract infections, and standard laboratory exposure levels that have been reported in the scientific literature. By 24 h, SNAP films led to >1 log reduction of adhered and viable E. coli at all tested microbial loads compared to control polydimethylsiloxane (PDMS). Further, SNAP films displayed no viable adhered S. aureus at the 10³ microbial level for the entire study and showed total planktonic killing by 8 h. NO localization within bacterial cells adhering to the films was evaluated, revealing higher NO uptake and consequent bacterial killing by SNAP samples. This unique study shows that NO-releasing polymers not only kill bacteria adhered to the polymer surface, but localized delivery leads to environmental planktonic bacterial killing that prevents adhesion from occurring. Furthermore, the promising findings of NO-releasing polymers in scientific research indicate their potential for successful application in clinical settings to prevent infections.