Photodynamic inactivation of Shigella flexneri by curcumin

This study aimed to inactivate Shigella flexneri using curcumin-based photosensitization and determine the sensitivity of S. flexneri to the combination of epsilon (ε)-polylysine (ε-PL) and curcumin-based photosensitization for decontamination. Bacterial numbers were reduced by 4.65 log CFU/mL after incubation with 80 μM curcumin and illumination for 20 min. Photosensitization resulted in cell morphology changes and increased cell permeability and protein degradation. Oxidative stress gene ( oxyR ) and efflux pump genes ( marA , acrA ) were upregulated. Decontamination of S. flexneri after incubation with curcumin and ε-PL for 1 h followed by photoactivation for 60 s has been investigated. It was found that the growth of bacteria was completely inhibited. Additionally, the number of bacteria was reduced by > 6 log CFU/mL. Experiments on the uptake of curcumin molecules by bacteria showed that ε-PL promoted the penetration of bacterial cells by curcumin, thus enhancing the effects of photosensitization.