EXPERIMENTAL DETERMINATION OF PHOTODYNAMIC INFLUENCE PARAMETERS ON A. ISRAELII AND P. MELANINOGENICA

Abstract

SUMMARY. The aim of the work is to determine experimentally the parameters of photodynamic influence on the viability of periodontal pathogenic anaerobic bacteria, on the example of A. israelii and P. melaninogenica.

Materials and methods. Cultures of isolated clinical strains of A. israelii and P. melaninogenica were used for research. The radiation source was a high-intensity LED with a light wavelength of 460–480 nm and a radiation power of 1200 mW/cm². The culture plate was irradiated for 30 seconds up to 5 minutes and left under anaerobic conditions at 37 ºC. The effect of “blue” light on the viability of cultures to be irradiated was evaluated by the number of grown colonies on a dense nutrient medium after 6, 12 and 24 hours of culturing bacterial suspension.

Results and Discussion. According to the results of the study, it was determined that when the culture was irradiated for 30 seconds, 1 and 2 minutes in the samples subjected to irradiation, there was no statistically significant reduction in viable cells compared to the control. When irradiated for 3, 4 and 5 minutes after 12 and 24 hours of cultivation, a significant (by 2–3 log) decrease in the amount of CFU/ml of culture was observed. These results allowed us to determine the duration of irradiation of A. israelii culture for 2 minutes as one that does not significantly affect the viability of cells and is optimal for studies of photodynamic microbial inactivation of A. israelii culture.

When irradiating a culture of P. melaninogenica for 30 seconds and 1 and 2 minutes in the samples there was no statistically significant decrease in the number of viable cells compared to the control during the entire culture period. At irradiation lasting 3 and 4 minutes after 12 hours of cultivation, a slight, statistically insignificant suppression of the intensity of culture growth was observed compared to the control, this trend was maintained after 24 hours of cultivation. At irradiation lasting 5 minutes after 12 hours of cultivation, a significant reduction of 100 and more times (up to 2–3 log) in the number of viable cells was observed. This trend persisted after 24 hours of culturing the microbial suspension. According to the results of the research it was established that the electromagnetic influence for 4 minutes did not lead to a statistically significant decrease in the viability of P. melaninogenica culture during the entire observation period.

Conclusions. According to the results of experiments, it was determined that when irradiating cultures of P. melaninogenica and A. israelii with a radiator with a power of 1200 mW/cm² and a wavelength of 460–480 nm, exposure for 4 and 2 minutes, respectively, did not lead to a statistically significant reduction in bacterial viability observation period. Our study to determine the parameters of photodynamic effects on isolated asporogenic anaerobic pathogens allowed us to select the optimal irradiation regimes for further research to create an original composition of PS for PDT purulent-inflammatory-periodontal disease.