Photodynamic Inactivation of <i>Legionella pneumophila</i> Biofilm Formation by Cationic Tetra- and Tripyridylporphyrins in Waters of Different Hardness
The bacterium <i>Legionella pneumophila</i> is still one of the probable causes of waterborne diseases, causing serious respiratory illnesses. In the aquatic systems, <i>L. pneumophila</i> exists inside free-living amoebae or can form biofilms. Currently developed disinfectio...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2021-08-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/22/16/9095 |
| Summary: | The bacterium <i>Legionella pneumophila</i> is still one of the probable causes of waterborne diseases, causing serious respiratory illnesses. In the aquatic systems, <i>L. pneumophila</i> exists inside free-living amoebae or can form biofilms. Currently developed disinfection methods are not sufficient for complete eradication of <i>L. pneumophila</i> biofilms in water systems of interest. Photodynamic inactivation (PDI) is a method that results in an antimicrobial effect by using a combination of light and a photosensitizer (PS). In this work, the effect of PDI in waters of natural origin and of different hardness, as a treatment against <i>L. pneumophila</i> biofilm, was investigated. Three cationic tripyridylporphyrins, which were previously described as efficient agents against <i>L. pneumophila</i> alone, were used as PSs. We studied how differences in water hardness affect the PSs’ stability, the production of singlet oxygen, and the PDI activity on <i>L. pneumophila</i> adhesion and biofilm formation and in biofilm destruction. Amphiphilic porphyrin showed a stronger tendency for aggregation in hard and soft water, but its production of singlet oxygen was higher in comparison to tri- and tetracationic hydrophilic porphyrins that were stable in all water samples. All three studied porphyrins were shown to be effective as PDI agents against the adhesion of the <i>L. pneumophila</i> to polystyrene, against biofilm formation, and in the destruction of the formed biofilm, in their micromolar concentrations. However, a higher number of dissolved ions, i.e., water hardness, generally reduced somewhat the PDI activity of all the porphyrins at all tested biofilm growth stages. |
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| ISSN: | 1661-6596 1422-0067 |