Avaliação da fotoinativação microbiana para as bactérias Escherichia coli e Staphylococcus aureus

Abstract

The development antibiotic resistant pathogens have resulted in an increasing number of severe infections and mortality caused by overuse and / or inappropriate medication. In this scenario, it is necessary to develop alternative methods that promote the inactivation of microbial growth without inducing resistance. Microbial photoinactivation may be a promising option in the treatment of microbial infections, mainly in superficial tissues, since this technique hardly causes resistance to microorganisms due to the large number of targets that oxygen radicals can affect. Basically, this technique involves the interaction of light at a suitable wavelength, a photosensitizer and molecular oxygen to produce reactive oxygen species, thus leading to death. This study aimed to evaluate the phototoxic activity of chlorophyll extract, pheophytin, eosin methylene blue and methylene blue on the bacteria Escherichia coli and Staphylococcus aureus when irradiated by the red light (625 nm). The used methodology was serial dilution using a microplate reader to perform the absorbance readings every 15 minutes for 24 hours. The light irradiation was from a lighting device with LED's red intensity of 16.25 mW/cm2. The results revealed that the four analyzed photosensitizers have bactericidal properties, causing a reduction in the microorganisms growth. However, the microbial process photoinhibition was also noted, with better results for chlorophyll extract at a concentration of 15.60 mg /mL for both bacteria and pheophytin at the same concentration, was only successful for the Gram positive bacterium.