Effectiveness of antimicrobial photodynamic therapy using a 660nm laser and methyline blue dye for inactivating Staphylococcus aureus biofilms in compact and cancellous bones: An in vitro study

• Published in: Photodiagnosis and photodynamic therapy Vol. 12; no. 2; pp. 276 - 281
• Main Authors: Rosa, Luciano Pereira, Silva, Francine Cristina da, Nader, Sumaia Alves, Meira, Giselle Andrade, Viana, Magda Souza
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-06-2015
• Subjects: Biofilm; Methylene blue; Microorganism; Photodynamic therapy; Staphylococcus aureus; Biofilm; Photodynamic therapy; Microorganism; Staphylococcus aureus; Methylene blue
• ISSN: 1572-1000; 1873-1597
• DOI: 10.1016/j.pdpdt.2015.01.001

•We evaluated the antimicrobial photodynamic therapy to inactivate S. aureus biofilms.•We used an in vitro model to form biofilms on bone tissues.•The experimental treatments showed a significant reduction compared with the control group.•Compact specimens showed the greatest reduction in biofilms compared with cancellous specimens.
New therapeutic modalities such as antimicrobial photodynamic therapy (APDT) has been investigated in order to be a valid alternative to the treatment of infections caused by different microorganisms. This work evaluated the in vitro effectiveness of Antimicrobial Photodynamic Therapy (APDT) using 660nm laser combined with methylene blue dye to inactivate Staphylococcus aureus (ATCC 25923) biofilms in compact and cancellous bones specimens.
Eighty specimens of compact bone and 80 specimens of cancellous bone were contaminated with a standard suspension of S. aureus and incubated for 14 days at 37°C to induce the formation of biofilms. The specimens were then divided into groups (n=10) according to the established treatment: PS-L- (control—no treatment), PS+L- (only AM for 5min in the dark), PS-L+90 (only laser irradiation for 90s), PS-L+180 (only laser irradiation for 180s), PS-L+300 (only laser irradiation for 300s), APDT90 (APDT for 90s), APDT180 (APDT for 180s), and APDT300 (APDT for 300s). The findings were statistically analyzed by ANOVA 5%.
All of the experimental treatments showed a significant reduction (log10CFU/mL) of S. aureus biofilms in compact and cancellous bones specimens compared with the control group, and the APDT group was the most effective. Compact specimens treated with APDT showed the greatest reduction in biofilms compared with cancellous specimens, regardless of length of treatment.
APDT with methylene blue dye and a 660nm laser proved to be effective in inactivating S. aureus biofilms formed in compact and cancellous bone.