Photodynamic antibacterial enhanced effect of methylene blue-gold nanoparticles conjugate on Staphylococcal aureus isolated from impetigo lesions in vitro study

Background: Staphylococcal aureus is the most common organism which has been encountered in impetigo infection. Gold nanoparticles can be used as a tool to deliver antimicrobials or to enhance photodynamic destruction of bacteria. Objective: To evaluate the photodynamic effect of methylene blue gold nanoparticles (MB-gold nanoparticles conjugate) on S. aureus which were isolated from impetigo lesions. Patient and methods: Twenty children were diagnosed clinically as impetigo, and aged from 3 to 5 years of both sexes were recruited in the study. Two bacteriological samples were collected from each patient, identified and cultured. Samples of S. aureus of a concentration of 10(-1) ml were divided into four groups. S. aureus was treated by MB-gold nanoparticles conjugate, gold nanoparticles, MB, and the fourth group served as a control group. Diode laser (660 nm) was used for photoactivation. The bacterial growth inhibition was determined by two methods: the percentage of reduction of viable bacteria count and the optical density (O.D) of bacterial growth. Results: The highest significant inhibitory effect on S. aureus was obtained with MB-gold nanoparticles conjugate when irradiated by diode laser 660 nm (P< 0.0001). The percentage of viable bacteria was 3%. The photoactivated gold nanoparticles showed a significant inhibitory effect on bacterial growth (P< 0.05). A non-significant inhibitory effect was elicited in other groups. Conclusion: The photoactivated MB-gold nanoparticles conjugate showed the maximum inhibitory effect on S. aureus activity. The gold nanoparticles proved efficacy as a drug delivery system. It enhanced the photodynamic antibacterial effect of methylene blue. (c) 2015 Elsevier B.V. All rights reserved.