Analysis of low level laser therapy in vitro cultures of bacteria and fungi

Abstract

Background: Low intensity laser therapy has been used to accelerate the ulcers healing due to its healing, anti-inflammatory, analgesic and anti-edematous effects. Contaminations by bacteria or fungi on these ulcers commonly happen, constituting a major complication of healing, but there is no consensus about laser therapy bactericidal or fungicidal effect. Aim: To analyze the effects of different times of appliantion using the 808nm and 660nm lasers on cultures of different bacterial species and fungi in vitro. Method: Photon Lase III -DMC was used, with the wavelengths of 660 and 808nm and 30mW, 60mW and 100mW of power, with different exposure time to laser irradiation. Fifteen Petri plates were prepared, 12 plates containing Gram-positive (3 Staphylococcus aureus plates, 3 nterococcus plates) and gram negative bacterias (3 Escherichia coli, 3 Klebsiella pneumonia plates) and 3 Petri plates with the fungi Candida albicans. Plates were randomly divided into 3 groups with 5 plates each group. Plates of Group 1 were irradiated with 660 nm laser at nine different points (A, A 1 , A 2 /B, B 1 , B 2 /C, C 1 , C 2 ), and points A/B/C reciebed only one application, points A 1 ,B 1 ,C 1 received 2 applications and points A 2 ,B 2 ,C 2 received 3 applications. Plates from group 2 where irradiated with 660nm also in nine diferente points, following the same criterea of group 1, while plate of group 3 where used as control, without irradiation. Groups 1 and 2 were irradiated with 144 J/cm² dose at point A (irradiation time of 2 minutes and 15 seconds), point B (irradiation time of 1 minute 7 seconds) and at point C (40 seconds). After the irradiations the plates were incubated for 24 hours. The cultures were visually examined to check the presence or not of the inhibition zone. In all the groups, no zone of inhibition nor growth were observed. Conclusion: Low intensity laser therapy (808nm and 660nm) did not produce bactericidal and/or bacteriostatic effects, and even no bio-stimulant effect on the bacteria.

Effects of Photodynamic Therapy on Staphylococcus Aureus Viability and Staphylocoagulase Activity, an Ex-Vivo Trial

“…Another study by Andraus et al has reported that low-level laser therapy (LLLT) with 660nm or 808nm lasers has no bactericidal effect and no hindrance growth in the illuminated region of plates at different irradiation times (2.15 min, 1.7min and 40 seconds) [24]. We hypotheses that the form of prepared bacterial biofilm for irradiation represents a critical factor to observe the effect of LLLT on bacterial growth and its intracellular biomolecules activities.…”

In Vitro Effect of Low-level Laser Therapy on Candida albicans Colonies Isolated From Patients Undergoing Radiotherapy for Head and Neck Cancer

“…33 Radiation absorbs chromophores that cause conformational changes in some molecules that produce free radicals, thus triggering disruption or damage to the membranes of bacteria and fungi. 34 On the other hand, some researchers argue that microbial cells are transparent to visible laser light and are not affected by radiation. Sensitizing the cell with a chemical dye before the laser treatment will help absorb the light of the laser wavelength and produce an excited triplet state.…”

“…LLLT also has fibrinolytic effects, anti-inflammatory effects that block prostaglandin synthesis, analgesic effects through secreting chemotaxis substances that stimulate endorphin release, and fungicidal and bactericidal effects by increasing the amount of interferon and damaging the cell wall that causes protein denaturation in the cytoplasm. 29,34 The specifications of a laser and the biological parameters of the microorganism affect laser treatment effectiveness. Important laser properties of influence include its wavelength, fluence or dose, irradiance, exposure time, emission mode (continuous or pulse), and number or frequency of exposures.…”

Photobiomodulation and Antimicrobial Photodynamic Influence of a 650 nm Wavelength on Staphylocoagulase and Viability of Staphylococcus aurous

“…We think that exposure of microorganisms to low-level laser treatment (LLLT) for an extended period, similar to the case of Chung ̓ s study, leads to a thermal effect instead of photo-biostimulation, and thermal accumulation actively limits the ionization of chromophore in intracellular biomolecules. 27,28 Another study by Andraus et al revealed that LLLT did not have any bactericidal effect with the light of 660 nm or 808 nm and any hindrance to growth in the illuminated region of plates at different irradiation times (2.15 minutes, 1.7 minutes and 40 seconds). 29 We hypothesize that the form of bacterial biofilm prepared for irradiation represents a critical factor in observing the action of LLLT on bacterial growth and its intracellular biomolecules activities.…”