Characterization of a rabbit model of staphylococcal osteomyelitis

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Abstract
We previously described a rabbit osteomyelitis model that involved the direct introductiof Staphylococcus aureus into devascularized bone. To further evaluate the model, we performed expeirijj aimed at correlating the microbiological, radiographic, and histologic parameters involved in the development of experimental osteomyelitis. Using the strain UAMS-1, we achieved an infection rate of 75% with an inoculum as small as 2 × 103 colony-forming unit's. However, development of significant radiographieja'TOifaife logic signs of disease required an inoculum of at least 2 × 104 colony-forming units. Radiographic singns were minimal 1 week after infection and progressed steadily to a maximum 3 weeks after infection.-, In contrasthistologic signs of disease were observed within 1 week and remained essentially unchanged throughout the4-week evaluation period. Unlike the results obtained with UAMS-1, rabbits infected with the heavily encapsulated Staphylococcus aureus, strain Smith diffuse exhibited little evidence of disease even whdrf'-inreicl with 2 × 106 colony-forming units. The reduced virulence of strain Smith diffuse was surprising given its greatly enhanced, Virulence (relative to UAMS-1) in a murine peritonitis model of staphylococcal disease. These results suggest that UAMS-1 expresses virulence factors that are important in the pathogeritesis of osteomyelitis and that some or all of these virulence factors are either absent or are not expressed jrisfraffl Smith diffuse. Most importantly, the results suggest that our model may be appropriate for the identificationf and characterization of these virulence factors.