Impact of methylene blue and LED radiation on microbial biofilms

Antibiotics pla y a key role in treating and controlling infectious diseases caused by pathogenic bacteria. Overconsumption and misuse of antibiotics have led to an increase in bacterial drug resistance. Resistant microorganisms are responsible for infe c tions that are more difficult and expensive to treat; besides multidrug-resistant microorganisms cause hundreds of thousands of deaths annually. To combat antibiotic resistance, physicochemical methods, including antimicrobial photodynamic therapy, are becoming increasingly widespread. The purpose of the study was to determine the complex effect of methylene blue as a phot o sensitizer, and LED radiation on the biofilms of some opportunistic microorganisms. To examine biofilm formation and the impact of photodynamic therapy on formed biofilms, the microtiter plate method was used. The obtained results showed that 20-minute exposure of LED light of red-infrared spectrum did not cause statistically significant effect on formed biofilms. Photose n sitizer methylene blue alone caused a certain antibiofilm effect which was expressed in a decrease in the growth intensity of bi o film scrapings after inoculation of appropriate dilutions into the Petri dishes on average by 33.2 – 60.0%, compar ed to the control group. The combined action of the photosensitizer with subsequent irradiation of biofilms by LED radiation demonstrated pr o nounced antibiofilm activity, which wa s much higher than the separate effects of specified factors. In this case, the growth inte n sity of the studied microorganisms at similar dilutions of biofilm scrapings decreased on average by 65.8 – 92.5%. Investigated strains of Staphylococcus aureus and Candida albicans were more susceptible than Escherichia coli , Klebsiella pneumonia , and Pseudomonas aeruginosa . Due to the lack of pronounced side effects and the presence of several advantages, including wide-spectrum antimicrobial and antibiofilm activity, antimicrobial photodynamic therapy can be used in the treatment of inflammat o ry-purulent processes particularly in dentistry and dermatology.