ABSTRACT
Sterile drinking water samples were artificially colonized with M. Kansasii, M. gordonae and M. fortuitum suspensions (the numbers of viable unite in 1 ml were 1.2 x 10(3), 48.5 and 3.2 x 10(3), respectively) prepared from mycobacterial strains replicated in Tween 80-free liquid Dubos medium STO. The contaminated water samples were irradiated from a rotary cobalt-60 source (gamma radiation, E = 1.17 and 1.33 MeV, dose intensity 1 kJ/kg.h at room temperature) with doses 0.7, 1.5, 2.2, 3, 9, 16 and 27 kJ/kg. The disinfecting effectiveness was assessed by direct cultivation tests (0.5 ml volumes of water inoculated on egg medium) and by cultivation on membrane filters after filtrating the whole amount of the water examined (about 500 ml). Fully positive disinfecting effects were recorded in M. kansasii and M fortuitum irradiated with 9 kJ/kg and in M. gordonae after irradiation with 1.5 kJ/kg. The calculated value of D10 = 0.4 kJ/kg (i.e. the dose radiation that reduces the number if viable mycobacteria by an order of magnitude) is suggestive of a strong disinfecting effect of ionizing radiation on the tested strains of potentially pathogenic mycobacteria. The results indicate that the use of ionizing radiation to disinfect mycobacteria that are difficult to remove with other methods which, as a rule, cannot ensure the permanent disinfection.
Subject(s)
Disinfection/methods , Mycobacterium/radiation effects , Nontuberculous Mycobacteria/radiation effects , Radiation, Ionizing , Sterilization/methods , Water Microbiology , Gamma Rays , Nontuberculous Mycobacteria/growth & developmentABSTRACT
Radiative and nonradiative processes were investigated in subchloroplast particles highly enriched in P-700 (1 P-700 to 10 chlorophyll molecules) according to the method of classical fluorescence and of photoacoustical spectroscopy. The envelope of fluorescence spectrum divided into three Gaussian bands and their quantum yields of fluorescence were calculated. Indpendently the quantum yield of fluorescence was determined from the spectral course of the photoacoustical signal. Finally, the estimate of the photochemical activity of P-700, based upon the measured fluorescence quantum yield and upon the measured nonradiative losses of excitation energy, was done.
