In vitro antimicrobial activity of LED irradiation on Pseudomonas aeruginosa

•5 min of 980 nm LED irradiation was able to reduce the P. aeruginosa count.•LED antibacterial activity increased with the irradiation time and energy output.•Methylene blue during LED irradiation did not influenced bacterial count.•Chlorhexidine added during LED irradiation increased antibacterial activity.

Pseudomonas aeruginosa is an opportunistic pathogen responsible of many deaths due to nosocomial pneumonia each year.It is particularly resistant to many different classes of antibiotics and disinfectants. For all these reasons, there is the necessity to find novel approaches of treatment.The aim of this study was to evaluate the effect of 880 nm light emitting diodes (LED) irradiation on P. aeruginosa, in vitro. Different LED irradiation parameters (time, energy output and the addition of methylene blue and chlorhexidine) have been tested in order to evaluate the effects on this bacterium. After treatment, the colony forming units per milliliter (CFU mL-1) were recorded and the data were submitted to ANOVA and Bonferroni post hoc tests at a level of significance of 5%.A statistical significant reduction of bacterial count has been registered after 5 min of LED irradiation. The antibacterial effect was directly proportional to irradiation time and the output energy. The pre-treatment with methylene blue, seems to be not effective against P. aeruginosa, independently from irradiation parameters. On the contrary, the contemporary action of LED and chlorhexidine has shown a great reduction of bacterial count that was statistical significant respect chlorhexidine and LED alone. The effect of LED irradiation was visible also after 24 h, when a lower bacterial count characterized all irradiated samples respect controls.