Experimental acute hematogenous osteomyelitis in mice. I. Histopathological and immunological findings

This study investigated immunological responses to Staphylococcus aureus bone infection. Because considerable immunological information is available on the mouse, a murine model of acute hematogenous osteomyelitis was established. Osteomyelitis was created in the proximal tibia of C3H/HeJ mice by a tibial epiphyseal fracture followed by intravenous bacterial inoculation with Staphylococcus aureus (strain LS-1). Swelling and warmth of the limb was found, and following limb exposure, abscess formation was evident in the proximal tibia. Histological examination revealed distortion primarily at the hypertrophic zone of the physis and polymorphonuclear leukocyte infiltration throughout the damaged area of the proximal tibia. Local infection was demonstrated at the fracture site, evidenced by the recovery of Staphylococcus aureus following microbiological analysis of tissue specimens. Polymerase chain reaction was utilized to detect 16S ribosomal prokaryotic nucleic acid to demonstrate that the diagnosis of osteomyelitis could be established in the absence of conventional microbiological techniques. The infected mice had an increase of circulating large leukocytes (granulocytes) and an elevation of total serum immunoglobulin. Flow cytometry revealed significant increases in splenic B lymphocytes and in lymph-node CD4+ T lymphocytes. These results indicate that an experimental model of acute hematogenous osteomyelitis that closely resembles the pathology of the disease in humans may be consistently induced in mice. Furthermore, marked immunological changes may be observed in response to the Staphylococcus aureus bone infection.