Antibacterial effect of semiconductor laser radiation against the strains of S. aureus and P. aeruginosa, leading pathogens in osteomyelitis

Abstract

Introduction The study of the antibacterial effect of photodynamic therapy against the leading pathogens of chronic osteomyelitis is one of the promising directions today. Purpose of the work was to evaluate the antibacterial effect against the strains of Staphylococcus aureus and Pseudomonas aeruginosa with the ALOD-01 laser system in the presence of photodithazine. Materials and methods The object of the study was 24-hour archival cultures of gram-positive and gram‑negative microorganisms belonging to two taxa: Staphylococcus aureus (25923), Pseudomonas aeruginosa (27853). The antibacterial effect after the exposure to laser radiation in the presence of photodithazine on the microbial cells of the studied cultures was assessed by the absence of microorganism growth in the area of the light beam. Results Laser exposure in combination with photodithazine (concentration 0.5–1.0 mg/ml) on S. aureus for two minutes at 200–300 J achieved a bactericidal effect in the beam area. A bactericidal effect on the entire surface of the Petri dish was achieved with light exposure of 400 J for 5 minutes and a photodithazine concentration of 1.0 mg/ml. Laser exposure for 2 minutes in the presence of photodithazine at a concentration of 0.5 mg/ml and 1 mg/ml did not have an antibacterial effect on P. aeruginosa strains. Continuous growth of microorganisms was observed on the dish. Increasing the light dose and exposure time contributed to a decrease in the growth of microbial cells. A bactericidal effect was obtained only in the center of the dish in treating the bacterial suspension with photodithazine at a concentration of 5 mg/ml. Discussion The effectiveness of PDT depends on the type of microorganisms, the anatomical location of the infection site, as well as the properties of the photosensitizer and the laser used. Depending on the structure of the cell wall, different susceptibility of bacteria to photodynamic effects is observed. Conclusion S. aureus strains can be successfully photoinactivated using photodithazine. For P. aeruginosa strains, it was not possible to find a regime in which microbial cell growth was absent throughout the dish. The photodynamic reaction occurs only when adequate doses of light energy act on the photosentisizer in the presence of oxygen in the medium, while the photodynamic damage is local and the bactericidal effect is limited by the zone of light exposure.

Keywords

• photodynamic therapy
• photodithazine
• chronic osteomyelitis
• antimicrobial effect