Antimicrobial Photodynamic Inactivation of Pseudomonas aeruginosa Biofilm

Pseudomonas aeruginosa is a difficult-to-treat human pathogen and remains a priority for which new antimicrobials are needed. Many photosensitizers are tested against planktonic cells, which do not accurately reflect the clinical challenge posed by biofilms. This study investigates the efficacy of chlorophyllin exposed to red light alone and in combination with the cationic permeabilizer polyethylenimine or the activator of mechanosensitive channels butylparaben against P. aeruginosa persister cells and biofilms. The broth microdilution checkerboard and colony biofilm methods were used to determine the bactericidal concentrations. Serine hydroxamate was used for the induction of persister cells via amino acid starvation. Results showed that chlorophyllin effectively eradicated P. aeruginosa biofilm cells. Persister cells exhibited more sensitivity to chlorophyllin/polyethylenimine combinations compared to growing cells, whereas they were less sensitive to chlorophyllin/butylparaben combinations. These findings underscore the antimicrobial effect of chlorophyllin against P. aeruginosa biofilms, with potential application against chronic wound infections