The relative antimicrobial effect of blue 405 nm LED and blue 405 nm laser on methicillin-resistant Staphylococcus aureus in vitro

Abstract

It has long been argued that light from a laser diode is superior to light from a light-emitting diode (LED) in terms of its effect on biological tissues. In order to shed light on this ongoing debate, we compared the antimicrobial effect of light emitted from a 405-nm LED with that of a 405-nm laser on methicillin-resistant Staphylococcus aureus (MRSA) at comparable fluences. We cultured 5 × 10(6) CFU/ml MRSA on tryptic soy agar and then irradiated culture plates once, twice, or thrice with either LED or laser light using 40, 54, 81, or 121 J/cm(2) fluence at 15-, 30-, or 240-min time interval between irradiation. Cultures were incubated immediately after irradiation at 37 °C for 24 h before imaging and counting remnant bacterial colonies. Regardless of the device used, LED or laser, irradiation at each fluence resulted in statistically significant bacterial growth suppression compared to non-irradiated controls (p < 0.0001). The antimicrobial effect of both light sources, LED and laser, was not statistically different at each fluence in 35 of the 36 experimental trials. Bacterial growth suppression achieved with either source of light increased with repeated irradiation, particularly at the 15- or 30-min treatment time interval. Thus, we conclude that the antimicrobial effect of 405-nm laser and 405-nm LED on MRSA is similar; neither has a superior antimicrobial effect when compared to the other.

Characterizing the Antimicrobial Properties of 405 nm Light and the Corning® Light‐Diffusing Fiber Delivery System

“…All organisms responded to 405 nm light delivered via an LDF system in a dose‐dependent manner and magnitude that paralleled the results of LED irradiation. P. aeruginosa, S. aureus, K. pneumoniae , and A. baumannii were all found to be highly susceptible to 405 nm light resulting in ≥4‐log 10 reduction in cell viability at ≤144 J/cm 2 , which mimics the results of LED delivered 405 nm light . Enterococcus was found to be recalcitrant to 405 nm light, which is also consistent to previous findings .…”

Antimicrobial blue light inactivation of pathogenic microbes: State of the art

“…Masson-Meyers et al compared the relative antimicrobial effect of non-coherent 405 nm LED and coherent 405 nm laser on MRSA (Masson-Meyers et al, 2015). Both the LED and laser irradiation at the exposures of 40–121 J/cm 2 resulted in statistically significant bacterial growth suppression.…”

Blue/violet laser inactivates methicillin-resistant Staphylococcus aureus by altering its transmembrane potential

“…(a) Bacterial culture (MRSA USA300, strain ATCC ® BAA-1680) from the American Type Culture Collection (Manassas, VA, USA) was diluted to a concentration of 5 x 10 6 CFU/mL, in 0.9% sterile saline, then streaked onto individual wells in 24-well microplates containing tryptic soy agar and subjected to single-or double-dose irradiation with 121 J/cm 2 405 nm laser light as described below. The time interval for the double irradiation was 30 minutes, based on our previous report [17]. After treatment, the microplates were incubated for 24 hours at 37°C.…”

“…At the end of the incubation period, standardized digital images of MRSA colonies were taken from 10 cm above each microplate, to ensure consistency of colony magnification. Colonies were then counted, and average survival rates and standard deviations were computed and plotted as detailed previously [12,[15][16][17].…”

“…The need to address this problem has prompted the pursuit of alternative therapies. Documented alternative therapies include a combination of honey and antibiotics [4], antibacterial clay [5], hyperbaric oxygen therapy [6,7] and irradiation with blue light [8][9][10][11][12][13][14][15][16][17]. Examples of conditions or infections which were successfully treated with blue light include acne vulgaris [18], eradication of Propionibacterium acnes [19], as well as different Gram-negative and Grampositive bacteria (including MRSA) upon pre-treatment with δ-aminolevulinic acid (ALA) to induce prior production of sensitizers, i.e., porphyrins [20,21].…”