Bacterial Photosensitization

Photomed Laser Surg. 2010 Aug;28 Suppl 1:S67-72.

Antimicrobial photodynamic therapy: photodynamic antimicrobial effects of malachite green on Staphylococcus, enterobacteriaceae, and Candida.

Junqueira JC, Ribeiro MA, Rossoni RD, Barbosa JO, Querido SM, Jorge AO.

Department of Biosciences and Oral Diagnosis, School of Dentistry of São José dos Campos, São Paulo State University/UNESP, São José dos Campos, São Paulo, Brazil. juliana@fosjc.unesp.br

Abstract

OBJECTIVE: This study investigated in vitro the photodynamic antimicrobial effects of the photosensitizer malachite green on clinical strains of Staphylococcus, Enterobacteriaceae, and Candida.

MATERIALS AND METHODS: Thirty-six microbial strains isolated from the oral cavity of patients undergoing prolonged antibiotic therapy, including 12 Staphylococcus, 12 Enterobacteriaceae, and 12 Candida strains, were studied. The number of cells of each microorganism was standardized to 10(6) cells/mL. Twenty-four assays were carried out for each strain according to the following experimental conditions: gallium-aluminum-arsenide laser and photosensitizer (n = 6, L+P+), laser and physiologic solution (n = 6, L+P-), photosensitizer (n = 6, L-P+), and physiologic solution (n = 6, L-P-). Next, cultures were prepared on brain-heart infusion agar for the growth of Staphylococcus and Enterobacteriaceae, and on Sabouraud dextrose agar for the growth of Candida, and incubated for 48 h at 37 degrees C. The results are reported as the number of colony-forming units (CFU/mL) and were analyzed with analysis of variance and the Tukey test.

RESULTS: The Staphylococcus, enterobacterial, and Candida strains were sensitive to photodynamic therapy with malachite green (L+P+). A reduction of approximately 7 log(10) for Staphylococcus, 6 log(10) for enterobacteria, and 0.5 log(10) for the genus Candida. Significant statistical differences were observed between the L+P+ groups and the control groups (L-P-).

CONCLUSION: The Staphylococcus, Enterobacteriaceae, and Candida strains studied were sensitive to photodynamic therapy with malachite green.

Lasers Med Sci. 2010 May;25(3):385-9. Epub 2009 Jul 5.

Comparison of the photodynamic fungicidal efficacy of methylene blue, toluidine blue, malachite green and low-power laser irradiation alone against Candida albicans.

Souza RC, Junqueira JC, Rossoni RD, Pereira CA, Munin E, Jorge AO.

Department of Biosciences and Oral Diagnosis, School of Dentistry of São José dos Campos, São Paulo State University (UNESP), Francisco José Longo 777, São Dimas, São José dos Campos 12245-000, SP, Brazil.

Abstract

This study was to evaluate specific effects of photodynamic therapy (energy density 15.8 J/cm(2), 26.3 J/cm(2) and 39.5 J/cm(2)) using methylene blue, toluidine blue and malachite green as photosensitizers and low-power laser irradiation on the viability of Candida albicans. Suspensions of C. albicans containing 10(6) cells/ml were standardized in a spectrophotometer. For each dye, 120 assays, divided into four groups according to the following experimental conditions, were carried out: laser irradiation in the presence of the photosensitizer; laser irradiation only; treatment with the photosensitizer only; no exposure to laser light or photosensitizer. Next, serial dilutions were prepared and seeded onto Sabouraud dextrose agar for the determination of the number of colony-forming units per milliliter (CFU/ml). The results were subjected to analysis of variance and the Tukey test (P < 0.05). Photodynamic therapy using the photosensitizers tested was effective in reducing the number of C. albicans.. The number of CFU/ml was reduced by between 0.54 log(10) and 3.07 log(10) and depended on the laser energy density used. Toluidine blue, methylene blue and malachite green were effective photosensitizers in antimicrobial photodynamic therapy against C. albicans, as was low-power laser irradiation alone.

Photochem Photobiol. 2009 Nov-Dec;85(6):1364-74.

Near-infrared photoinactivation of bacteria and fungi at physiologic temperatures.

Bornstein E<>, Hermans W<>, Gridley S<>, Manni J<>.

Nomir Medical Technologies, Waltham, MA, USA. ebornstein@nomirmedical.com

We examined a laser system (870 and 930 nm), employing wavelengths that have exhibited cellular photodamage properties in optical traps. In vitro, with 1.5 cm diameter flat-top projections (power density of 5.66 W cm(-2)), at physiologic temperatures, we achieved photoinactivation of Staphylococcus aureus, Escherichia coli, Candida albicans and Trichophyton rubrum. Using nonlethal dosimetry, we measured a decrease in trans-membrane potentials (DeltaPsimt and DeltaPsip) and an increase in reactive oxygen species (ROS) generation in methicillin-resistant S. aureus (MRSA), C. albicans and human embryonic kidney cells. We postulate that these multiplexed wavelengths cause an optically mediated mechano-transduction of cellular redox pathways, decreasing DeltaPsi and increasing ROS. The cellular energetics of prokaryotic and fungal pathogens, along with mammalian cells, are affected in a similar manner when treated with these multiplexed wavelengths at the power densities employed. Following live porcine thermal tolerance skin experiments, we then performed human pilot studies, examining photodamage to MRSA in the nose and fungi in onychomycosis. No observable damage to the nares or the nail matrix was observed, yet photodamage to the pathogens was achieved at physiologic temperatures. The selective aspect of this near-infrared photodamage presents the possibility for its future utilization in human cutaneous antimicrobial therapy.

Acta Odontol Latinoam. 2009;22(2):93-7.

In vitro lethal photosensitization of S. mutans using methylene blue and toluidine blue O as photosensitizers.

Araújo PV<>, Teixeira KI<>, Lanza LD<>, Cortes ME<>, Poletto LT<>.

Departamento de Odontologia Restauradora da Faculdade de Odontologia da Universidade Federal de Minas Gerais, Brazil. patbhz@terra.com.br<>

Abstract

The purpose of this in vitro study was to evaluate the antimicrobial effect of photodynamic therapy on Streptococcus mutans (A TCC 25175) suspensions, using a red laser for one minute in combination with toluidine blue O (TBO) or methylene blue (MB). Both photosensitizers were used in three concentrations (25, 10 and 5 mg/L). The activity of photosensitizers and laser irradiation were tested separately on the bacteria, as well as the irradiation of this light source in the presence of the TBO or MB. These groups were compared to a control group, in which the microorganism did not receive any treatment. The activity of both TBO and MB or laser irradiation, alone, were not able to reduce the number of S. mutans. In the groups of lethal photosensitization, a bacterial reduction of 70% for TBO and 73% for MB was observed when these photosensitizers were used at 25 mg/L and a reduction of 48% was observed for MB at 5mg/L. In other concentrations there were no significant differences in comparison to the control group. Both the TBO and the MB at 25 mg/L associated with a red laser had an excellent potential for use in PDT in lethal sensitization of S. mutans.

J Periodontal Res. 2003 Aug;38(4):428-35.

Lethal photosensitization of periodontal pathogens by a red-filtered Xenon lamp in vitro.

Matevski D<>, Weersink R<>, Tenenbaum HC<>, Wilson B<>, Ellen RP<>, Lépine G<>.

Faculty of Dentistry, University of Toronto, University of Toronto, Ontario, Canada.

Abstract

BACKGROUND: The ability of Helium-Neon (He-Ne) laser irradiation of a photosensitizer to induce localized phototoxic effects that kill periodontal pathogens is well documented and is termed photodynamic therapy (PDT).

OBJECTIVES: We investigated the potential of a conventional light source (red-filtered Xenon lamp) to activate toluidine blue O (TBO) in vitro and determined in vitro model parameters that may be used in future in vivo trials.

MATERIALS AND METHODS: Porphyromonas gingivalis 381 was used as the primary test bacterium.

RESULTS: Treatment with a 2.2 J/cm2 light dose and 50 micro g/ml TBO concentration resulted in a bacterial kill of 2.43 +/- 0.39 logs with the He-Ne laser control and 3.34 +/- 0.24 logs with the lamp, a near 10-fold increase (p = 0.028). Increases in light intensity produced significantly higher killing (p = 0.012) that plateaued at 25 mW/cm2. There was a linear relationship between light dose and bacterial killing (r2 = 0.916); as light dose was increased bacterial survival decreased. No such relationship was found for the drug concentrations tested. Addition of serum or blood at 50% v/v to the P. gingivalis suspension prior to irradiation diminished killing from approximately 5 logs to 3 logs at 10 J/cm2. When serum was washed off, killing returned to 5 logs for all species tested except Bacteroides forsythus (3.92 +/- 0.68 logs kill).

CONCLUSIONS: The data indicate that PDT utilizing a conventional light source is at least as effective as laser-induced treatment in vitro. Furthermore, PDT achieves significant bactericidal activity in the presence of serum and blood when used with the set parameters of 10 J/cm2, 100 mW/cm2 and 12.5 micro g/ml TBO.

J Chemother. 2003 Aug;15(4):329-34.

Comparative antistreptococcal activity of photobactericidal agents.

O’Neill J, Wilson M, Wainwright M.

Department of Microbiology, Eastman Dental Institute, University College London, 256 Gray’s Inn Road, London WC1X 8LD, UK.

Abstract

In order to establish a comparative order of efficacy among established photosensitising compounds currently under investigation, the in vitro photobactericidal activities of six commercially available photosensitisers were investigated at equal concentration against Streptococcus sanguis using a Helium Neon (HeNe) laser (632.8 nm). Of the photosensitisers used, the four phenothiazinium compounds were efficient photobactericidal agents as was the protoporphyrin IX salt. However, the zinc phthalocyaninetetrasulfonate was less effective. Of the active agents, 1,9-dimethyl Methylene Blue (DMMB) was notable in achieving complete bacterial kill when used at a concentration of 40.85 microM in conjunction with a light energy dose of 21.8 J cm(-2), although there was inherent dark activity associated with this compound. Since each of the photosensitisers is well known to produce singlet oxygen, the relative activities exhibited are thought to be due to differences in bacterial cell uptake, which in turn are related to the physicochemical properties of the photosensitisers, in particular, to the combination of lipophilicity and ionic character.

J Appl Microbiol. 2002;92(4):618-23.

Factors influencing the susceptibility of Gram-negative bacteria to toluidine blue O-mediated lethal photosensitization.

Kömerik N, Wilson M.

Department of Microbiology, Eastman Dental Institute for Oral Health Care Sciences, University College London, UK.

Abstract

AIMS: Bacteria can be killed by red light in the presence of a photosensitizer. The purpose of this study was to evaluate the effect of physiological and environmental factors on the susceptibility of some bacteria associated with oral infections in immunocompromised patients to killing by the photosensitizer toluidine blue O (TBO).

METHODS AND RESULTS: Suspensions of Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae in human saliva, horse serum or saline were exposed to light from a helium/ neon laser in the presence of TBO. Additional suspensions at various growth phases and pHs were treated in an identical manner. Survivors were enumerated by viable counting. All three species were susceptible to lethal photosensitization under all of the conditions tested. The presence of serum and, to a lesser extent, saliva decreased the level of kill attained. The bactericidal effect was reduced at acid pHs but was unaffected by the growth phase of the organism.

CONCLUSIONS: The composition and pH of the fluid in which bacteria are suspended influenced the effectiveness of TBO-mediated lethal photosensitization, whereas killing was unaffected by the growth phase of the organism.

SIGNIFICANCE AND IMPACT OF THE STUDY: Environmental factors operating in the mouths of patients with mucositis could reduce the effectiveness of TBO-mediated lethal photosensitization of bacteria associated with this condition.

Phys Ther. 1999 Sep;79(9):839-46.

Bactericidal effect of 0.95-mW helium-neon and 5-mW indium-gallium-aluminum-phosphate laser irradiation at exposure times of 30, 60, and 120 seconds on photosensitized Staphylococcus aureus and Pseudomonas aeruginosa in vitro.

DeSimone NA<>, Christiansen C<>, Dore D<>.

Veterans Administration Medical Center, 507 Fulton St, Durham, NC 27705, USA. noelledes@aol.com<>

Erratum in:

Phys Ther 1999 Nov;79(11):1082.

Abstract

BACKGROUND AND PURPOSE: Studies have demonstrated a bactericidal effect of laser irradiation when lasers with power outputs of (6 mW are directed toward pathogenic or opportunistic bacteria previously treated with a photosensitizing agent. The purpose of this study was to determine the bactericidal capabilities of irradiation from lasers with power outputs of less than 6 mW on photosensitized microorganisms.

METHODS: Two bacteria that commonly infect skin lesions, Staphylococcus aureus and Pseudomonas aeruginosa, were used. The 2 lasers used, the 0.95-mW helium -neon laser and the 5-mW indium-gallium-aluminum-phosphate laser, emit light at a wavelength close to the absorption maxima of the sensitizing agent chosen, toluidine blue O. This agent was used because of its proven effectiveness in sensitizing bacteria. For each bacterial strain, toluidine blue O was added to a 108 cells/mL solution until a 0.01% weight/volume ratio was obtained. These mixtures were spread on agar-coated petri dishes, which were then exposed to 1 of the 2 lasers for 30, 60, and 120 seconds. The cultures were then grown overnight and examined for one or more visible zones of inhibition. The areas surrounding the irradiated zone provided a control for the effects of toluidine blue O alone. To determine the effects of laser irradiation without prior toluidine blue O sensitization, separate plates were established using unsensitized bacteria.

RESULTS: Although inconsistencies between plates were noted, both lasers produced at least one zone of inhibition in both bacterial species at all 3 time periods. The 5-mW laser, however, produced a greater number of these zones.

CONCLUSION AND DISCUSSION: Laser-induced microbial killing of photosensitized organisms could have clinical applications in the treatment of infected skin lesions, pending in vivo studies.

J Antimicrob Chemother. 1997 Dec;40(6):873-6.

Killing of methicillin-resistant Staphylococcus aureus in vitro using aluminum disulphonated phthalocyanine, a light-activated antimicrobial agent.

Griffiths MA<>, Wren BW<>, Wilson M<>.

Department of Microbiology, Eastman Dental Institute for Oral Health Care Sciences, University of London, UK.

Abstract

The aim of this study was to determine whether 16 epidemic methicillin-resistant strains of Staphylococcus aureus (EMRSA) could be killed by the light-activated antimicrobial agent aluminium disulphonated phthalocyanine (AIPcS2). EMRSA suspensions were irradiated with light from a laser diode in the presence of AIPcS2 and survivors enumerated. All strains were susceptible to killing, the bactericidal effect being dependent on the AIPcS2 concentration and the light dose. AIPcS2 rendered the bacteria light-sensitive almost immediately and killing was unaffected by the growth phase of the organism. Scavengers of singlet oxygen and free radicals protected the bacteria from killing. These results imply that light-activated antimicrobial agents may be useful in eliminating EMRSA from wounds or carriage sites.

Photochem Photobiol. 1997 Jun;65(6):1026-31.

Effect of dosimetric and physiological factors on the lethal photosensitization of Porphyromonas gingivalis in vitro.

Bhatti M<>, MacRobert A<>, Meghji S<>, Henderson B<>, Wilson M<>.

Department of Microbiology, Eastman Dental Institute for Oral Health Care Sciences, University of London, UK.

Abstract

The aims of this study were to (1) determine the effect of dosimetric and physiological factors on the lethal photosensitization of Porphyromonas gingivalis using toluidine blue O (TBO) and light from a helium/neon (HeNe) laser; (2) determine the influence of sensitizer concentration, preirradiation time, serum and growth phase on sensitizer uptake by P. gingivalis. The dosimetric factors studied were concentration of TBO, light dose and preirradiation time. The physiological factors were presence of serum, pH and bacterial growth phase. Sensitizer uptake by P. gingivalis under various conditions was determined using tritiated TBO (3H-TBO). In the presence of TBO, a light dose-dependent increase in kill was attained (100% kill at 4.4 J). There was no significant effect on the numbers killed when TBO was increased from 12.5 to 50 micrograms/mL. An increase in preirradiation time gave slightly increased kills. High kills were achieved at all three pH (6.8-8.0). Although kills were substantial in the presence of serum, they were significantly less than those obtained in the presence of saline. Cells in all three growth phases were susceptible to lethal photosensitization, although stationary phase cells were slightly less susceptible. Maximum uptake of TBO occurred within 60 s and uptake in serum was less than in saline. The uptake by the log phase cells was greater at lower concentrations of sensitizer (50 micrograms/mL), compared to the other two phases.

Med Microbiol. 1996 Apr;44(4):245-52.

The killing of Helicobacter pylori by low power laser light in the presence of a photosensitiser.

Millson CE<>, Wilson M<>, Macrobert AJ<>, Bedwell J<>, Bown SG<>.

The National Medical Laser Centre, University College London Medical School, UK.

Abstract

Helicobacter pylori is associated with various gastrointestinal disorders. Lethal photosensitisation was investigated as a possible technique for killing H. pylori which might offer a better alternative to antibiotics. The susceptibility of H. pylori to lethal photosensitisation was determined by mixing suspensions of H. pylori with various photosensitisers and plating out on blood agar before irradiation with low-power laser light. Five sensitisers were studied further by mixing them with H. pylori in a tissue-culture plate and counting survivors after irradiation as a function of laser exposure time, dye concentration and pre-irradiation time. Crystal violet and thionine were ineffective as sensitisers, but zones of inhibition appeared with methylene blue (MB), protoporphyrin IX (PPIX), haematoporphyrin derivative (HPD), toluidine blue O (TBO) and disulphonated aluminium phthalocyanine (S2). Laser light or sensitiser alone did not affect bacterial viability. S2 (100 microg/ml) with a laser light energy density of 16 J/cm2, HPD (10O microg/ml) with 160 J/cm2, MB (100 microg/ml) with 21 J/cm2, PPIX (150 microg/ml) with 320 J/cm2 and TBO (50 microg/ml) with 160 J/cm2 all reduced bacterial viability by >99%. The killing of sensitised H. pylori by laser light offers a new approach to the treatment of localised infections when all colonised areas are accessible to light.

J Antimicrob Chemother. 1996 Feb;37(2):377-81.

Killing of Streptococcus sanguis in biofilms using a light-activated antimicrobial agent.

Wilson M<>, Burns T<>, Pratten J<>.

Department of Microbiology, Eastman Dental Institute of Oral Health Care Sciences, University of London, UK.

Abstract

The aim of this study was to determine whether Streptococcus sanguis, when in a biofilm, could be killed using a light-activated antimicrobial agent. Biofilms were grown on hydroxyapatite, irradiated with up to 12.2 J of light from a gallium aluminium arsenide laser in the presence of aluminium disulphonated phthalocyanine (AlPcS2) and survivors enumerated. No significant decrease in the viable count was found when either the AlPcS2 or the laser light was used alone. There was a light dose related decrease in the viable counts of irradiated AlPcS2-treated biofilms. No viable streptococci were detectable following irradiation with 12.2 J of laser light.

J Photochem Photobiol B. 1996 Jan;32(1-2):59-65.

Ex-vivo treatment of gastric Helicobacter infection by photodynamic therapy.

Millson CE<>, Wilson M<>, MacRobert AJ<>, Bown SG<>.

National Medical Laser Centre, University College London Medical School, UK.

Abstract

Attempts to develop PDT for eradication of Helicobacter infection have only been successful in vitro. We have investigated the effect of topical sensitization (except ALA) of Helicobacter mustelae on explanted ferret gastric mucosa using one of five sensitizers (methylene blue (MB), toluidine blue O (TBO), phthalocyanine, haematoporphyrin derivative and 5-aminolavulinic acid), followed by irradiation with an appropriately tuned copper vapour pumped dye laser. A 90% reduction in counts of bacteria sensitized with 0.75 mg TBO kg-1 were seen after irradiation with 200 J cm-2. Concentrations of MB of 0.75 mg kg-1 and 7.5 mg kg-1 were not toxic to H. mustelae, but the further addition of 20 J cm-2 laser light reduced colony counts by more than 99%. MB at a concentration of 75 mg kg-1 exhibited significant dark toxicity towards H. mustelae, but further addition of 20 J cm-2 laser light resulted in near eradication of all colonies. The remaining three compounds were ineffective. Finally, we studied the microscopic fluorescence distribution of MB (7.5 mg kg-1) on ferret gastric mucosa after topical administration. Fluorescence was greatest in the superficial mucosal layer, upon which lies the bacteria. However, from experiments on rats, the energy required to kill the sensitized bacteria was insufficient to damage the underlying mucosa. We conclude that Helicobacter can be killed on host mucosal epithelium following topical administration of MB and subsequent exposure to laser light.

Acta Univ Palacki Olomuc Fac Med. 1996;140:43-6.

In vitro He-Ne laser effect on some immunological functions of polymorphonuclears and monocytes in rabbits.

Luza J<>, Hubácek J<>.

Department of Physiology, Medical Faculty, Palacký University, Olomouc, Czech Republic.

The aim of this study is to evaluate in vitro the effect of Helium-Neon (He-Ne) laser irradiation on the viability, adherence, phagocytic activity of the polymorphonuclears and monocytes. Also the level of metabolic processes in phagocytizing blood cells, monocytes and polymorphonuclears was estimated and evaluated by the INT-test. Evaluation of the leukocyte adherence, the method of MacGregor was used. Phagocytic activity was examined by classical method using microspherical hydrophilic particles (Hema-particles). He-Ne laser in a small dosage (< or = 0.8 J) increases the leukocyte adherence, after higher laser irradiation dosage (> 1.2 J) the leukocyte adherence is decreased. The laser effect on the phagocytic activity of both types of blood cells, polymorphonuclears and monocytes is similar. Small dosage of the laser irradiation increases the phagocytic activity, and after higher laser irradiation phagocytic activity is decreased. Also the changes of the level of metabolic processes in the phagocytizing cells are very similar with the changes of phagocytic activity. The viability of the blood cells examined after higher laser irradiation is gradually decreased.

Caries Res. 1995;29(3):192-7.

Effect of dentine and collagen on the lethal photosensitization of Streptococcus mutans.

Burns T<>, Wilson M<>, Pearson GJ<>.

Department of Microbiology, Eastman Dental Institute for Oral and Dental Health Care Sciences, London, UK.

Abstract

Suspensions of the cariogenic bacterium, Streptococcus mutans were treated with either toluidine blue O or aluminium disulphonated phthalocyanine and then exposed to light from a helium-neon or gallium-aluminium-arsenide laser, respectively, after passing through demineralized dentine slices. Bacteria were also embedded in a collagen matrix prior to sensitization and exposure to the laser light. When dentine slices were interposed between the laser light and the bacterial suspension, substantial kills (10(7) CFU) were achieved at energy doses of 876, 1,752, and 3,504 mJ with the helium-neon laser and of 1,188, 2,376, and 4,752 mJ with the gallium-aluminium-arsenide laser. There was no apparent relationship between the extent of killing and the degree of demineralization of the dentine. Prolonging the exposure of the sensitized bacteria to the laser light increased the kill achieved. Substantial numbers (10(8) to 10(10) CFU) of S. mutans were also killed when embedded in a collagen matrix and exposed to 438 and 1,314 mJ of helium-neon laser light and 594 and 1,782 mJ of light from the gallium-aluminium-arsenide laser. These results imply that lethal photosensitization may be effective at killing S. mutans in a carious lesion, even when the organism is embedded in demineralized dentine.

J Appl Bacteriol. 1995 May;78(5):569-74.

Bacteria in supragingival plaque samples can be killed by low-power laser light in the presence of a photosensitizer.

Wilson M<>, Burns T<>, Pratten J<>, Pearson GJ<>.

Department of Microbiology, Eastman Dental Institute for Oral Health Care Sciences, University of London, UK.

Abstract

The purpose of this study was to determine whether bacteria in supragingival plaque samples could be killed by low-power laser light in the presence of a suitable photosensitizer. Plaque samples were obtained from 10 volunteers, treated with either toluidine blue O (TBO) or aluminum disulphonated phthalocyanine (AlPcS2), and then exposed to light from a helium/neon (HeNe) or gallium aluminium arsenide (GaAs) laser respectively. Following irradiation, substantial reductions were achieved in the total anaerobic count as well as in the number of viable streptococci and actinomyces present in the samples. In the absence of laser light, the sensitizers themselves had little effect on the viability of the bacteria in the plaque samples. The HeNe/TBO combination appeared to be more effective than the GaAs/AlPcS2 combination, achieving log10 reductions of 2.95, 5.40 and 3.34 in the total anaerobic count, streptococci and actinomyces respectively with a light energy dose of 1.31 J. If effective in vivo, lethal photosensitization may be useful as a means of eliminating plaque bacteria from a carious lesion prior to its restoration.

Int Dent J. 1994 Apr;44(2):181-9.

Bactericidal effect of laser light and its potential use in the treatment of plaque-related diseases.

Wilson M.

Department of Microbiology, Institute of Dental Surgery, University of London, UK.

Abstract

Chemical antibacterial agents are increasingly being used in prophylactic and therapeutic regimes for plaque-related diseases. As these agents can be rendered ineffective by the development of resistance in the target organisms there is a need to develop alternative antimicrobial approaches. Light from high-power lasers is known to be bactericidal and investigations have shown that it is effective against organisms implicated in caries and inflammatory periodontal diseases. However, the adverse effects of such light on dental hard tissues argue against its use solely as an antibacterial agent. Although light from low-power lasers has no adverse effect on bacterial viability, bacteria can be sensitised to killing by such light by prior treatment with a chemical photosensitising agent. Lethal photosensitisation of a wide range of cariogenic and periodontopathogenic bacteria has been demonstrated using light from a helium/neon or gallium aluminium arsenide laser in conjunction with a dye such as toluidine blue or aluminium disulphonated phthalocyanine as a photosensitiser. The advantages of the technique are that killing is achieved in very short periods of time (< 60 s), resistance development in the target bacteria would be unlikely and damage to adjacent host tissues can be avoided. This approach may be a useful alternative to antibiotics and antiseptics in eliminating cariogenic and periodontopathogenic bacteria from disease lesions.

Microbios. 1994;78(316):163-8.

Lethal photosensitization of Staphylococcus aureus.

Wilson M, Pratten J.

Department of Microbiology, Institute of Dental Surgery, University of London, Great Britain.

Abstract

The purpose of this study was to determine whether toluidine blue O (TBO) could sensitise Staphylococcus aureus to killing by light from a low-power helium/neon (HeNe) laser. Suspensions of the organism were irradiated with light from a HeNe laser in the presence and absence of TBO and the survivors enumerated. A 95% reduction (9 x 10(7) cfu) in the viable count was achieved following irradiation with 0.88 J of HeNe laser light in the presence of 12.5 micrograms/ml TBO whereas no significant reductions in viability were found when suspensions were exposed to this dose of laser light in the absence of TBO. With higher doses (3.5 J) of laser light statistically significant kills (3 x 10(7) cfu) were obtained in the absence of TBO implying the presence of an endogenous photosensitiser in the organism.

J Med Microbiol. 1993 Jun;38(6):401-5.

Sensitization of cariogenic bacteria to killing by light from a helium-neon laser.

Burns T, Wilson M, Pearson GJ.

Department of Microbiology, Institute of Dental Surgery, London.

Abstract

Suspensions of the cariogenic bacteria Streptococcus mutans, S. sobrinus, Lactobacillus casei and Actinomyces viscosus were exposed to light from a 7.3-mW helium-neon laser in the presence of toluidine blue O. A substantial killing rate (c. 10(6) cfu) of all four species was achieved with a dye concentration of 50 micrograms/ml and a light energy dose of 33.6 J/cm2. This was achieved in 60 s, an exposure time that is clinically acceptable. Exposure to laser light in the absence of the dye did not significantly affect the viability of any of the organisms. This approach may be useful in dentistry to sterilise a carious lesion prior to its repair.

Oral Microbiol Immunol. 1993 Jun;8(3):182-7.

Sensitization of periodontopathogenic bacteria to killing by light from a low-power laser.

Wilson M, Dobson J, Sarkar S.

Microbiology Department, Institute of Dental Surgery, London, United Kingdom.

Abstract

Cultures of Porphyromonas gingivalis, Fusobacterium nucleatum and Actinobacillus actinomycetemcomitans were treated with a range of photosensitizers and then exposed to light from a 7.3 mW helium/neon laser for up to 80 s. Toluidine blue O (25 micrograms/ml) and methylene blue (25 micrograms/ml) were effective lethal photosensitizers of all 3 target organisms, enabling substantial light dose-related reductions in viable counts. Dihaematoporphyrin ester and aluminium disulphonated phthalocyanine were lethal photosensitizers only of P. gingivalis. In the absence of a photosensitizer, exposure to laser light had no significant effect on the viability of the cultures. If such low doses of light (22 J/cm2) are effective at killing bacteria in vivo, the technique may be useful as a means of eliminating periodontopathogenic bacteria from diseased sites.

J Periodontal Res. 1993 May;28(3):204-10.

Lethal photosensitization of bacteria in subgingival plaque from patients with chronic periodontitis.

Sarkar S, Wilson M.

Department of Microbiology, Institute of Dental Surgery, London, England.

Abstract

Subgingival plaque samples from patients with chronic periodontitis were exposed to light from a 7.3 mW Helium/Neon laser for 30 s in the presence and absence of 50 micrograms/ml toluidine blue O as a photosensitizer. Viable counts of various groups and species of bacteria were carried out before and after irradiation. The median numbers of viable bacteria initially present in the 30-microliters aliquots irradiated were 1.13 x 10(5) cfu (aerobes), 4.08 x 10(5) cfu (anaerobes), 4.92 x 10(3) cfu (black-pigmented anaerobes), 4.75 x 10(2) cfu (Porphyromonas gingivalis), 6.15 x 10(3) cfu (Fusobacterium nucleatum) and 1.7 x 10(4) cfu (streptococci). The dye/laser combination achieved significant reductions in the viability of these organisms, the median reductions in the viable counts being 91.1% for aerobes, 96.6% for anaerobes, 100% for black-pigmented anaerobes, P. gingivalis and F. nucleatum and 94.2% for streptococci. Overall, the viability of bacteria in the 20 plaque samples was not significantly decreased by the dye alone. However, in a small minority of samples there were indications of light-independent, dye-induced toxicity. Low-power lasers, in conjunction with appropriate photosensitizers, may be a useful adjunct to mechanical debridement in the treatment of inflammatory periodontal diseases if a similar effectiveness against subgingival plaque bacteria can be achieved in vivo.

Arch Oral Biol. 1992 Nov;37(11):883-7.

Sensitization of oral bacteria in biofilms to killing by light from a low-power laser.

Dobson J, Wilson M.

Microbiology Laboratory, Institute of Dental Surgery, London, U.K.

Abstract

Biofilms of Streptococcus sanguis, Porphyromonas gingivalis, Fusobacterium nucleatum and Actinobacillus actinomycetemcomitans were prepared on the surfaces of agar plates and a number of compounds were screened for their ability to sensitize bacteria in these biofilms to killing by light from a 7.3 mW Helium/Neon (He/Ne) laser. Toluidine blue O and methylene blue enabled detectable killing of all four target organisms after exposure to He/Ne light for 30 s. Aluminium disulphonated phthalocyanine, haematoporphyrin HCl and haematoporphyrin ester were effective photosensitizers of only some of the target organisms. These findings suggest that lethal photosensitization may be an effective means of eliminating periodontopathogenic bacteria from dental plaque.

Curr Microbiol. 1992 Aug;25(2):77-81.

Sensitization of oral bacteria to killing by low-power laser radiation.

Wilson M, Dobson J, Harvey W.

Microbiology Laboratory, Institute of Dental Surgery, London, UK.

Abstract

Twenty-seven compounds were screened for their ability to sensitize Streptococcus sanguis to killing by light from a 7.3-mW Helium/Neon (HeNe) laser. Bacteria were mixed with various concentrations of the test compounds, spread over the surfaces of agar plates, and then exposed to light from the HeNe laser for various time periods. The plates were then incubated and examined for zones of inhibition. Those compounds found to be effective photosensitizers were then tested against Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, and Fusobacterium nucleatum. Toluidine blue O, azure B chloride, and methylene blue at concentrations of 0.005% (wt/vol) were effective photosensitizers of all four species, enabling killing of bacteria following exposure to laser light for only 30 s.