Blue Light Compromises Bacterial β-Lactamases Activity to Overcome β-Lactam Resistance

In this study, we evaluated the effectiveness of antimicrobial blue light (aBL; 410 nm wavelength) against β-lactamase-carrying bacteria and the effect of aBL on the activity of β-lactamases.

Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae strains carrying β-lactamases as well as a purified β-lactamase enzymes were studied. β-lactamase activity was assessed using a chromogenic cephalosporin hydrolysis assay. Additionally, we evaluated the role of porphyrins in the photoreaction, as well as protein degradation by sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Finally, we investigated the bactericidal effect of combined aBL-ceftazidime exposure against a metallo-β-lactamase expressing P. aeruginosa strain.

Our study demonstrated that aBL effectively killed β-lactamase-producing bacteria and reduced β-lactamase activity. After an aBL exposure of 1.52 J/cm², a 50% reduction in enzymatic activity was observed in P. aeruginosa. Additionally, we found a 40% decrease in the photoreaction activity of porphyrins following an aBL exposure of 64.8 J/cm². We also revealed that aBL reduced β-lactamase activity via protein degradation (after 136.4 J/cm²). Additionally, aBL markedly improved the bactericidal effect of ceftazidime (by >4-log₁₀) in the metallo-β-lactamase P. aeruginosa strain.

Our results provide evidence that aBL compromises bacterial β-lactamase activity, offering a potential approach to overcome β-lactam resistance in bacteria.