| Popis: |
Legionella pneumophila, a Gram-negative bacterium and member of the group of waterborne opportunistic premise plumbing pathogens (OPPPs), can cause serious lung infections, known as Pontiac disease, or life-threatening pneumonia, called Legionnaires’ disease. L. pneumophila’s main habitat is natural waters and soils, where this bacterium can survive and multiply even under low nutrient and oxygen conditions, high temperatures and is resistant to many antibiotics and disinfectants [1]. The under- explored occurrence of Legionella in wastewater treatment plants also poses a serious threat to public health [2]. In our previous work, complete eradication of L. pneumophila with photoactivated tetracationic pyridinium-3-yl porphyrin (TMPyP3) was achieved, as well as inhibition of adhesion to polystyrene, and destruction of the biofilm in waters of varying hardness [3]. Metal complexation of porphyrins often increases their chemical stability, and chelation with metal ions such as Zn(II) can promote intersystem crossing, leading to an increased lifetime of the triplet excite state and singlet oxygen (1O2) production [4], which in turn could be useful for water disinfection applications. Municipal wastewater poses a possible challenge for photodynamic inactivation (PDI) due to the presence of organic matter, suspended solids and dissolved minerals. In our study of the influence of Zn(II) chelation and different wavelength irradiation on PDI against L. pneumophila in municipal wastewater, spectroscopic properties and stabilities of TMPyP3 and its Zn(II) complex (Zn(II)-TMPyP3) were evaluated, as well as their 1O2 production. Antimicrobial activity was investigated using violet light (394 nm, 20 mW/cm2), from the wavelength range known by the term violet-blue light (VBL), which is also used as a standalone disinfectant, and orange light (607 nm, 2 mW/cm2), a wavelength corresponding to the absorption spectra of both porphyrins. The results obtained by exposures to single wavelength, as well as the application of different combinations with both wavelengths will be presented. |
