Activity of electrical current in experimental Propionibacterium acnes foreign-body osteomyelitis

Foreign-body-associated infections are often difficult to treat, given that the associated microorganisms are in a biofilm state. Previously, we showed that a low-amperage direct electrical current (DC) reduces Propionibacterium acnes biofilms formed on implant-associated materials in vitro. In this study, low-amperage DC was compared to ceftriaxone treatment or no treatment in a novel rat femur model of foreign-body osteomyelitis. A platinum implant seeded with a P. acnes biofilm (10⁷ CFU/cm²) and 10⁹ CFU of planktonic P. acnes was placed in the femoral medullary cavity. One week later, rats were assigned to one of three treatment groups: no treatment, ceftriaxone treatment, or 200-μA-DC treatment. After 2 weeks of treatment, there were fewer bacteria in the bones of the ceftriaxone group (3.06 log₁₀ CFU/g of bone [P = 0.0209]) and the 200-μA-DC group (0.5 log₁₀ CFU/g [P = 0.0015]) than in those of the control group (6.58 log₁₀ CFU/g). The DC-exposed animals exhibited fewer bacteria than the ceftriaxone-treated animals (P = 0.0330). There were fewer bacteria on the implanted wires in the groups treated with ceftriaxone (0.1 log₁₀ CFU/cm²) or a 200-μA DC (0.1 log₁₀ CFU/cm²) than in the control group (2.53 log₁₀ CFU/cm² [P, 0.0003 for both comparisons]). Low-amperage DC may be useful for treating, or aiding in the treatment of, foreign-body infections caused by P. acnes.