A new preclinical approach for treating chronic osteomyelitis induced by Staphylococcus aureus: in vitro and in vivo study on photodynamic antimicrobial therapy (PAmT)

Abstract

Osteomyelitis is an acute or chronic inflammation in the marrow spaces in the superficial or cortical bone, and can be associated with bacterial or fungal infections. Chronic osteomyelitis represents a major health problem due to its difficult treatment and increased morbidity. Photodynamic antimicrobial therapy (PAmT) is a treatment based on a cytotoxic photochemical reaction in which a bright light produced by a laser system and an active photosensitizer absorbed by cells leads to a process of activation that induces a series of metabolic reactions that culminates a bacterial killing. The aim of the present randomized study was to evaluate, by in vitro and in vivo microbiological analysis, the effects of PAmT on tibial surgical bone defects in rats infected by Staphylococcus aureus using bacterial counts carried out immediately and after 30 days after treatment as outcome measure. In the preliminary in vitro study, a diode laser (λ660 nm; 40 mW; ϕ = 0.4 cm(2); 5 or 10 J/cm(2)) and 5, 10, and 15 μg/mL toluidine blue were tested, and the best parameter was chosen for the in vivo study. The concentration of 5 μg/mL was selected to perform the decontamination of S. aureus-infected tibial bone defects in rats. The findings were subjected to statistical analysis. For all PAmTs groups, with the different concentrations, treatment showed significant reductions (p < 0.001) in the amount of bacteria. The in vivo study PAmT group presented a bacterial reduction of 97.4% (p < 0.001). The PAmT using toluidine blue was effective in reducing the number of S. aureus in both in vitro and in vivo studies.

Photodynamic Antimicrobial Chemotherapy (PACT) in osteomyelitis induced by Staphylococcus aureus: Microbiological and histological study

“…A previous in vitro study [12] carried out by our team provided valuable information on the response of S. aureus to different protocols using PACT and indicated one that could be effective on in vivo testing. The best result obtained from the in vitro study (5 lg/mL and 10 J/cm 2 ) was chosen for the present investigation.…”

“…The best parameter obtained in the previous in vitro [12] study was then adopted: k660 nm, 40 mW, £ = 0.4 cm 2 , CW, 10 J/cm 2 .…”

“…The PS links itself to a target microorganism and is activated by the light at specific wavelength causing the release of reactive oxygen species (ROS). Increased levels of ROS may cause cell death by exhausting the molecules of ATP and lipid peroxidation [3,[11][12][13][14].…”

“…Among alternatives that have been investigated to treat osteomyelitis is lethal photosensitization or photodynamic antimicrobial therapy, which uses lasers in combination with substances as a potential antimicrobial therapy [11][12][13][14]. The light is emitted by a low power laser that activated a specific photosensitizer (PS) which triggers biochemical changes capable of suppressing bacterial growth.…”

The Effects of Transpositional Muscle Flaps Transfected with Vascular Endothelial Growth Factor Gene in the Treatment of Experimental Osteomyelitis

“…In spite of advances in both antibiotics and surgical treatment, the long-term recurrence rate remains approximately 20-30%. [21] Due to dissatisfaction with actual treatment modalities, many experimental and clinical approaches to osteomyelitis therapy have been described in the literature.…”