4.6 Article

Photodynamic inactivation of multidrug-resistant strains of Klebsiella pneumoniae and Pseudomonas aeruginosa in municipal wastewater by tetracationic porphyrin and violet-blue light: The impact of wastewater constituents

Journal

PLOS ONE
Volume 18, Issue 8, Pages -

Publisher

PUBLIC LIBRARY SCIENCE
DOI: 10.1371/journal.pone.0290080

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With the increasing threat of multidrug-resistant strains of bacteria spreading into the environment and drinking water, there is a need to discover effective methods for treating municipal wastewater. Photodynamic inactivation (PDI) may be a way to stop the spread of antibiotic-resistant genes by combining a photosensitiser and light to generate reactive species that react with bacteria. This study investigated the effect of TMPyP3, a photosensitiser, on MDR strains of Pseudomonas aeruginosa and Klebsiella pneumoniae in tap water and municipal wastewater, and found significant toxicity and PDI effect after activation with violet-blue light.
There is an increasing need to discover effective methods for treating municipal wastewater and addressing the threat of multidrug-resistant (MDR) strains of bacteria spreading into the environment and drinking water. Photodynamic inactivation (PDI) that combines a photosensitiser and light in the presence of oxygen to generate singlet oxygen and other reactive species, which in turn react with a range of biomolecules, including the oxidation of bacterial genetic material, may be a way to stop the spread of antibiotic-resistant genes. The effect of 5,10,15,20-(pyridinium-3-yl)porphyrin tetrachloride (TMPyP3) without light, and after activation with violet-blue light (VBL) (394 nm; 20 mW/cm2), on MDR strains of Pseudomonas aeruginosa, Klebsiella pneumoniae and K. pneumoniae OXA-48 in tap water and municipal wastewater was investigated. High toxicity (similar to 2 mu M) of TMPyP3 was shown in the dark on both strains of K. pneumoniae in tap water, while on P. aeruginosa toxicity in the dark was low (50 mu M) and the PDI effect was significant (1.562 mu M). However, in wastewater, the toxicity of TMPyP3 without photoactivation was much lower (12.5-100 mu M), and the PDI effect was significant for all three bacterial strains, already after 10 min of irradiation with VBL (1.562-6.25 mu M). In the same concentrations, or even lower, an anti-adhesion effect was shown, suggesting the possibility of application in biofilm control. By studying the kinetics of photoinactivation, it was found that with 1,562 mu M of TMPyP3 it is possible to achieve the complete destruction of all three bacteria after 60 min of irradiation with VBL. This study confirmed the importance of studying the impact of water constituents on the properties and PDI effect of the applied photosensitiser, as well as checking the sensitivity of targeted bacteria to light of a certain wavelength, in conditions as close as possible to those in the intended application, to adjust all parameters and perfect the method.

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