Mycobacterium smegmatis Response to Blue Light Exposure
Mycobacterium smegmatis Response to Blue Light Exposure
Objective. To determine the potential for blue light (405 nm) to produce a bactericidal effect on Mycobacterium smegmatis. Additionally, the study sought to evaluate a series of doses in terms of their respective bactericidal capabilities.
Background Data. The effect of blue light on Staphylococcus aureus has been studied and it was found that a bactericidal outcome can be obtained with low doses of blue light.
Methods.M. smegmatis was tested because of the recent appearance of the Mycobacterium family of organisms as a public health threat among persons receiving tattoos. The organism was treated in vitro with 405 nm light emitted from a supraluminous diode (SLD) array. Doses of 60 Jcm, 90 Jcm, 120 Jcm, 150 Jcm, 180 Jcm, 215 Jcm, and 250 Jcm were used. Colony counts were performed and compared to untreated controls using Student t tests and one-way ANOVA with Tukey post hoc analysis.
Results. The results revealed statistically significant bactericidal effects of the blue light on M. smegmatis (F6, 28 = 50.518, P = 0.000). The treatment reduced the number of bacterial colonies at all doses, but 60 Jcm did not produce a statistically significant kill rate. All other doses produced a significant kill rate with 120 Jcm, 150 Jcm, and 215 Jcm, demonstrating the most effective kill rates of 98.3%, 96.7%, and 100%, respectively. Conclusions. Appropriate doses of 405 nm light from an SLD array can kill M. smegmatisin vitro. A dose of at least 100 Jcm dose is needed for the most effective inactivation of the organism. The dose response for this organism to blue light is not linear. Some degree of effectiveness is lost at 180 Jcm and 250 Jcm.
For several decades, antibiotics have been the treatment of choice for fighting infections. As effective as they have been, the development of antimicrobial resistance may bring an end to this era of antibiotic use. New Delhi metallo-ß-lactamase-1(NDM-1), an enzyme that renders some bacteria resistant to almost all antibiotics, has recently been found in the United States. It is a common concern that bacteria associated with infectious diseases will become unresponsive to antibiotic treatment. This concern has led to increased interest in light therapy as an alternative to antibiotic treatment.
Light therapy has the ability to provide equal killing effectiveness regardless of antibiotic resistance. Commonly employed sources of light therapy include photodynamic therapy (PDT), ultraviolet C (UVC) light, and blue light. Currently, there is no evidence of microbial resistance to PDT, giving it great potential for fighting infections. However, PDT requires the addition of exogenous photosensitizers. Another source of light therapy, UVC light, is known to inhibit bacterial growth, but has produced detrimental effects such as burns, premature aging, suppression of the immune system, and even skin cancers on mammalian cells and host tissue. While all 3 are effective sources of light therapy, blue light can be administered without the addition of exogenous photosensitizers and is less harmful to human skin.
Blue light has demonstrated a dose-dependent bactericidal effect on a number of organisms. For instance, 405 nm and 470 nm blue light achieved a bactericidal effect on both Staphylococcus aureus and Pseudomonas aeruginosa, in vitro. In another study, 405 nm blue light resulted in inactivation of Shigella sonnei, Escherichia coli, Salmonella enterica, Listeria monocytogenes, and Mycobacterium terrae. The mechanism of blue light inactivation is not completely understood. It is believed that bacterial inactivation results from the photo-excitation of porphyrins and the subsequent production of cytotoxic reactive oxygen species.
The genus Mycobacterium includes some very noteworthy pathogenic species that cause significant morbidity and mortality. The most well-known species, Mycobacterium tuberculosis and Mycobacterium leprae, cause tuberculosis and leprosy. Pathogens from the Mycobacterium tuberculosis complex such as M. bovis and M. tuberculosis remain among the most serious causes of infective disease worldwide. Recently, M. chelonae skin infections were reported in 14 New York residents who received tattoos between September 2011 and December 2011. Blue light therapy has shown potential to be an effective treatment of Mycobacteria in vitro.
Studies using PDT, UV, and blue light have demonstrated a bactericidal effect on Mycobacteria, but this outcome is not universal in all conditions. In a study on photodynamic therapy of M. smegmatis, it was discovered that photosensitizers must be cationic to achieve inactivation. Ultraviolet light is commonly used for disinfection of food and water. Ultraviolet light has demonstrated a reduction in M. avium complex organisms when treating water, but the same is not the case when pasteurizing milk. Obviously, research is necessary to determine the bactericidal effect of light therapy on Mycobacteria under various conditions and using specific techniques.
While research regarding blue light and Mycobacteria is developing, a bactericidal effect has recently been demonstrated. When a dose between 144 Jcm and 288 Jcm was administered, 405 nm blue light was shown to inactivate M. terrae by 4–5 log10 (CFU mL). To determine the most effective and least detrimental dose of blue light, a pattern of inactivation must be developed. Furthermore, to understand the impact blue light may have on fighting infection, microbial resistance must be determined. The purpose of this research was to evaluate, in vitro, the bactericidal effect of blue light on M. smegmatis in a similar fashion to the work by Murdoch et al.
Abstract and Introduction
Abstract
Objective. To determine the potential for blue light (405 nm) to produce a bactericidal effect on Mycobacterium smegmatis. Additionally, the study sought to evaluate a series of doses in terms of their respective bactericidal capabilities.
Background Data. The effect of blue light on Staphylococcus aureus has been studied and it was found that a bactericidal outcome can be obtained with low doses of blue light.
Methods.M. smegmatis was tested because of the recent appearance of the Mycobacterium family of organisms as a public health threat among persons receiving tattoos. The organism was treated in vitro with 405 nm light emitted from a supraluminous diode (SLD) array. Doses of 60 Jcm, 90 Jcm, 120 Jcm, 150 Jcm, 180 Jcm, 215 Jcm, and 250 Jcm were used. Colony counts were performed and compared to untreated controls using Student t tests and one-way ANOVA with Tukey post hoc analysis.
Results. The results revealed statistically significant bactericidal effects of the blue light on M. smegmatis (F6, 28 = 50.518, P = 0.000). The treatment reduced the number of bacterial colonies at all doses, but 60 Jcm did not produce a statistically significant kill rate. All other doses produced a significant kill rate with 120 Jcm, 150 Jcm, and 215 Jcm, demonstrating the most effective kill rates of 98.3%, 96.7%, and 100%, respectively. Conclusions. Appropriate doses of 405 nm light from an SLD array can kill M. smegmatisin vitro. A dose of at least 100 Jcm dose is needed for the most effective inactivation of the organism. The dose response for this organism to blue light is not linear. Some degree of effectiveness is lost at 180 Jcm and 250 Jcm.
Introduction
For several decades, antibiotics have been the treatment of choice for fighting infections. As effective as they have been, the development of antimicrobial resistance may bring an end to this era of antibiotic use. New Delhi metallo-ß-lactamase-1(NDM-1), an enzyme that renders some bacteria resistant to almost all antibiotics, has recently been found in the United States. It is a common concern that bacteria associated with infectious diseases will become unresponsive to antibiotic treatment. This concern has led to increased interest in light therapy as an alternative to antibiotic treatment.
Light therapy has the ability to provide equal killing effectiveness regardless of antibiotic resistance. Commonly employed sources of light therapy include photodynamic therapy (PDT), ultraviolet C (UVC) light, and blue light. Currently, there is no evidence of microbial resistance to PDT, giving it great potential for fighting infections. However, PDT requires the addition of exogenous photosensitizers. Another source of light therapy, UVC light, is known to inhibit bacterial growth, but has produced detrimental effects such as burns, premature aging, suppression of the immune system, and even skin cancers on mammalian cells and host tissue. While all 3 are effective sources of light therapy, blue light can be administered without the addition of exogenous photosensitizers and is less harmful to human skin.
Blue light has demonstrated a dose-dependent bactericidal effect on a number of organisms. For instance, 405 nm and 470 nm blue light achieved a bactericidal effect on both Staphylococcus aureus and Pseudomonas aeruginosa, in vitro. In another study, 405 nm blue light resulted in inactivation of Shigella sonnei, Escherichia coli, Salmonella enterica, Listeria monocytogenes, and Mycobacterium terrae. The mechanism of blue light inactivation is not completely understood. It is believed that bacterial inactivation results from the photo-excitation of porphyrins and the subsequent production of cytotoxic reactive oxygen species.
The genus Mycobacterium includes some very noteworthy pathogenic species that cause significant morbidity and mortality. The most well-known species, Mycobacterium tuberculosis and Mycobacterium leprae, cause tuberculosis and leprosy. Pathogens from the Mycobacterium tuberculosis complex such as M. bovis and M. tuberculosis remain among the most serious causes of infective disease worldwide. Recently, M. chelonae skin infections were reported in 14 New York residents who received tattoos between September 2011 and December 2011. Blue light therapy has shown potential to be an effective treatment of Mycobacteria in vitro.
Studies using PDT, UV, and blue light have demonstrated a bactericidal effect on Mycobacteria, but this outcome is not universal in all conditions. In a study on photodynamic therapy of M. smegmatis, it was discovered that photosensitizers must be cationic to achieve inactivation. Ultraviolet light is commonly used for disinfection of food and water. Ultraviolet light has demonstrated a reduction in M. avium complex organisms when treating water, but the same is not the case when pasteurizing milk. Obviously, research is necessary to determine the bactericidal effect of light therapy on Mycobacteria under various conditions and using specific techniques.
While research regarding blue light and Mycobacteria is developing, a bactericidal effect has recently been demonstrated. When a dose between 144 Jcm and 288 Jcm was administered, 405 nm blue light was shown to inactivate M. terrae by 4–5 log10 (CFU mL). To determine the most effective and least detrimental dose of blue light, a pattern of inactivation must be developed. Furthermore, to understand the impact blue light may have on fighting infection, microbial resistance must be determined. The purpose of this research was to evaluate, in vitro, the bactericidal effect of blue light on M. smegmatis in a similar fashion to the work by Murdoch et al.
