Pre-clinical in vitro and in vivo studies to examine the potential use of photodynamic therapy in the treatment of osteomyelitis

摘要

Osteomyelitis can lead to severe morbidity and even death resulting from an acute or chronic inflammation of the bone and contiguous structures due to fungal or bacterial infection. Incidence approximates 1 in 1,000 neonates and 1 in 5,000 children in the United States annually and increases up to 0.36% and 16% in adults with diabetes or sickle cell anaemia, respectively. Current regiments of treatment include antibiotics and/or surgery. However, the increasing number of antibiotic resistant pathogens suggests that alternate strategies are required. We are investigating photodynamic therapy (PDT) as one such alternate treatment for osteomyelitis using a bioluminescent strain of biofilm-producing staphylococcus aureus (SA) grown onto kirschner wires (K-wire). SA-coated K-wires were exposed to methylene blue (MB) or 5-aminolevulinic acid (ALA)-mediated PDT either in vitro or following implant into the tibial medullary cavity of Sprague-Dawley rats. The progression of SA biofilm was monitored non-invasively using bioluminescence and expressed as a percentage of the signal for each sample immediately prior to treatment. SA infections were subject to PDT 10 days post inoculation. Treatment comprised administration of ALA (300 mg/Kg) intraperitoneally followed 4 hr later by light (635 ± 10 nm; 38 or 75 J/cm~2) delivered transcutaneously via an optical fiber placed onto the tibia. In vitro, MB and ALA displayed similar cell kill with ≥ 4log_(10) cell kill. In vivo, ALA-mediated PDT inhibited biofilm implants in bone. These results confirm that MB or ALA-mediated PDT have potential to treat SA cultures grown in vitro or in vivo using an animal model of osteomyelitis.