Characterization of a rabbit model of staphylococcal osteomyelitis

TLDR

We previously described a rabbit osteomyelitis model that involved the direct introduction of Staphylococcus aureus into devascularized bone. To further evaluate the model, we performed experiments aimed at correlating the microbiological, radiographic, and histologic parameters involved in the development of experimental osteomyelitis. The study used a rabbit model with direct inoculation of Staphylococcus aureus into devascularized bone, correlating microbiological, radiographic, and histologic data to assess osteomyelitis development. In the UAMS‑1 strain, a 75 % infection rate was achieved with 2 × 10³ CFU, while significant radiographic and histologic disease required ≥2 × 10⁴ CFU and progressed over 3 weeks; the encapsulated Smith diffuse strain caused minimal disease even at 2 × 10⁶ CFU, indicating that UAMS‑1 expresses osteomyelitis‑relevant virulence factors absent in Smith diffuse and that the model is suitable for identifying these factors.

Abstract

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 × 10 3 colony‐forming unit's. However, development of significant radiographieja'TOifaife logic signs of disease required an inoculum of at least 2 × 10 4 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 × 10 6 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.