The Effect of 650 nm Diode Laser on Growth Curve of Gram-negative Bacteria and Their Phagocytic killing Assay by PMN Cells.

Nowadays laser in medicine is a rapidly growing field in both researches and applications and many studies have been done in bacteriology against different types of lasers. The effect of the laser depends on many factors, one of the laser factors was the wavelength. The red wavelength band has been considered as a stimulated wavelength for prokaryotic and eukaryotic cells. In this study, three clinical species of Gram-negative bacteria (E. coli, Proteus mirabilis, and Pseudomonas aeruginosa) were exposed to 650 nm band of red region wavelength by a diode laser. The effect of that wavelength appeared on the growth curves for each species along 3 days after laser treatment. The energy density (E.D.) 2.8 J/cm^2 gave a positive effect on growth curve for these three species, while the 5.6 J/ cm^2 have a stimulation effect on both P. aeruginosa and E. coli. The Phagocytic killing Assay (PKA) by PMN cells was tested against irradiated bacteria, and the 2.8 J/cm^2 appeared to have a significant (P 0.05) effect on PKA of all that three types of bacteria, on the other hand the 5.6 J/cm^2 affected significantly (P 0.05) on the PKA of P. mirabilis, and P. aeruginosa. These findings suggested that the E.D. 2.8 J/cm^2 was much effective than the 5.6 J/cm^2 on the growth curves and PKA values of the three bacteria species.