Related Experiment Video
Updated: Jul 5, 2025
The Synergistic Effect of Visible Light and Gentamycin on Pseudomona aeruginosa Microorganisms
Published on: July 2, 2013
In vitro study: methylene blue-based antibacterial photodynamic inactivation of Pseudomonas aeruginosa
Laiq Zada1,2, Shahzad Anwar3, Sana Imtiaz2
1Applied Environmental and Geo-Microbiology Lab, Department of Microbiology, Quaid-i-Azam University, Islamabad, 45320, Pakistan.
Abstract:
Pseudomonas aeruginosa is one of the most antibiotic-resistant and opportunistic pathogens in immunocompromised and debilitated patients. It is considered the cause of most severe skin infections and is frequently found in hospital burn units. Due to its high antibiotic resistance, eliminating P. aeruginosa from skin infections is quite challenging. Therefore, this study aims to assess the novel in vitro antibacterial activity of methylene blue using a 635-nm diode laser to determine the effective power and energy densities for inhibition of P. aeruginosa. The strain was treated with various concentrations of methylene blue and 635-nm diode laser at powers of 300 mW/cm2 and 250 mW/cm2. The diode laser's potency in the photo-destruction of methylene blue and its degradation through P. aeruginosa were also evaluated. Colony-forming unit (CFU)/ml, fluorescence spectroscopy, optical density, and confocal microscopy were used to measure the bacterial killing effect. As a result, the significant decrease of P. aeruginosa was 2.15-log10, 2.71-log10, and 3.48-log10 at 60, 75, and 90 J/cm2 after excitation of MB for 240, 300, and 360 s at a power of 250 mW/cm2, respectively. However, a maximum decrease in CFU was observed by 2.54-log10 at 72 J/cm2 and 4.32-log10 at 90 and 108 J/cm2 after 300 mW/cm2 of irradiation. Fluorescence images confirmed the elimination of bacteria and showed a high degree of photo-destruction compared to treatment with methylene blue and light alone. In conclusion, MB-induced aPDT demonstrated high efficacy, which could be a potential approach against drug-resistant pathogenic bacteria. KEY POINTS: • Combination of methylene blue with 635-nm diode laser for antibacterial activity. • Methylene blue photosensitizer is employed as an alternative to antibiotics. • aPDT showed promising antibacterial activity against Pseudomonas aeruginosa.
Insights
Methylene blue combined with a 635-nm diode laser shows potent antibacterial effects against drug-resistant Pseudomonas aeruginosa. This photodynamic therapy offers a promising alternative to antibiotics for treating severe skin infections.
Area of Science:
- Photomedicine
- Antimicrobial photodynamic therapy (aPDT)
- Bacteriology
Background:
- Pseudomonas aeruginosa is a highly antibiotic-resistant opportunistic pathogen causing severe skin infections, particularly in immunocompromised individuals.
- Current treatments for P. aeruginosa infections are challenged by the pathogen's extensive drug resistance.
- Novel therapeutic strategies are urgently needed to combat multidrug-resistant bacterial infections.
Purpose of the Study:
- To evaluate the in vitro antibacterial activity of methylene blue (MB) combined with a 635-nm diode laser against Pseudomonas aeruginosa.
- To determine optimal power and energy densities of the 635-nm diode laser for effective P. aeruginosa inhibition.
- To assess the photodynamic inactivation of P. aeruginosa using MB and laser irradiation.
Main Methods:
- In vitro susceptibility testing of P. aeruginosa to various concentrations of methylene blue and 635-nm diode laser irradiation (250 mW/cm² and 300 mW/cm²).
- Quantification of bacterial viability using colony-forming unit (CFU)/ml counts.
- Assessment of bacterial elimination via fluorescence spectroscopy, optical density measurements, and confocal microscopy.
Main Results:
- Significant reductions in P. aeruginosa CFU/ml were observed with increasing energy densities, reaching up to 4.32-log₁₀ at 90-108 J/cm² with 300 mW/cm² irradiation.
- Methylene blue-induced photodynamic therapy (aPDT) demonstrated superior bacterial elimination compared to MB or laser light alone.
- Fluorescence imaging confirmed effective bacterial photo-destruction and elimination.
Conclusions:
- Methylene blue-mediated aPDT is a highly effective strategy for inhibiting antibiotic-resistant Pseudomonas aeruginosa in vitro.
- This approach presents a viable alternative to conventional antibiotics for treating challenging bacterial skin infections.
- Further research into aPDT could lead to new treatments for multidrug-resistant pathogens.
More Related Videos
05:12An In Vitro Model to Study the Effect of 5-Aminolevulinic Acid-mediated Photodynamic Therapy on Staphylococcus aureus Biofilm
Published on: April 16, 2018
05:13LED-Based In Vitro Screening for Assessing Photoactivable Molecules in Bacterial Photodynamic Inactivation
Published on: January 24, 2025