The photodynamic effect of porphyrin on Legionella

Legionella pneumophila is a gram-negative bacterium whose natural habitat is water, including rivers, lakes and streams. L pneumophila is the cause of Pontiac fever and Legionnaires' disease. Contaminated water distribution systems and air humidifiers are just some of the infection sources. Despite the implementation of antiepidemic measures, the occurrence of Legionnaires' disease is increasingly frequent, thus requiring a development of new methods for removing legionella from water. One of the approaches is antimicrobial photodynamic therapy, which involves the joint action of photosensitizer, molecular oxygen and visible light of a certain wavelength to produce singlet oxygen and reactive oxygen species that kill the microbial cell. In this paper, minimum inhibitory and minimum bactericidal concentrations of different porphyrins on L pneumophila were determined with broth dilution method. We used red light in the total dose of 24 J cm(-2), while the illumination lasted 10 minutes. The strongest antibacterial effect was established for amphipathic porphyrin. Further studies on the efficiency of these compounds and the use of photodynamic therapy in the inactivation of Legionella in water are required.