A novel canine model of acute pyogenic spondylodiscitis

New, appropriate in vivo animal models are needed for the study of the pathogenesis of spinal infections and the development of novel anti-infection strategies. The purpose of this study was to develop a canine model of acute pyogenic spondylodiscitis which can best mimic the human spinal infection process, characterized by separately inoculating bacterial suspension into the lumbar intervertebral spaces of a single animal. A total of 14 dogs were used in this study. An inoculation containing Staphylococcus aureus and sodium morrhuate was injected into the intervertebral spaces. Two pilot studies were carried out to determine the most appropriate concentration of the bacterium inoculum. Before the inoculation, the intervertebral disks were partially removed and the end plates of the adjacent two vertebrae were deliberately curetted out to make space for the inoculum and to more thoroughly expose the neighboring vertebrae to the bacterial inoculum. The dogs were euthanized at 14 days postimplantation. The bacterial loads of the infected tissues were assayed. Spondylodiscitis of the lumbar spinal column was consistently produced in 90% (nine out of ten) of the sites challenged with 10(2) colony-forming units (CFU) of S. aureus. Liver biopsy and blood culture did not show signs of systematic infections at 14 days postsurgery. Two out of four animals implanted with the suspension at a concentration higher than 10(3) CFUs were dead within 3 days postimplantation. The results indicate that this new canine model of acute pyogenic spondylodiscitis could be used to test the efficacy of different anti-infection strategies.