Photodynamic Inactivation of Mycobacterium tuberculosis Using Alluminium Phthalocyanine

In a series of in vitro experiments, the optimum regimes of laser treatment were determined for effective photodynamic inactivation of Mycobacterium tuberculosis at a constant dose of aluminum phthalocyanine. Reference laboratory drug-susceptible strain H37Rv and clinical isolates of M. tuberculosis with varying degrees of resistance to antibiotics were used. Suspensions of M. tuberculosis were incubated with aluminum phthalocyanine in a concentration of 5 μg/ml and then subjected to photodynamic inactivation with high- or low- intensity laser irradiation at λ=662 nm at various parameters of light power density. Mycobacteria survival rate was assessed by CFU assay on solid media. It was shown that at the specified dose of the photosensitizer, the photodynamic inactivation of mycobacterium was characterized by inhibition and complete cessation of their growth depending on the dose density of the laser energy. Effective photodynamic inactivation started from a light dose density of 46.9 J/cm² at a radiation power of 0.01 W and from 56.25 J/cm² at a radiation power of 0.1 W. Photodynamic inactivation at low laser power is more effective against drug-susceptible strains of M. tuberculosis.