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 cor
relating the microbiological, radiographic, and histologic parameters
involved in the development of experimental osteomyelitis. Using the s
train UAMS-1, we achieved an infection rate of 75% with an inoculum as
small as 2 x 10(3) colony-forming units. However, development of sign
ificant radiographic and histologic signs of disease: required an inoc
ulum of at least 2 x 10(4) colony-forming units. Radiographic signs we
re minimal 1 week after infection and progressed steadily to a maximum
3 weeks after infection. In contrast. histologic signs of disease wer
e observed within 1 week and remained essentially unchanged throughout
the: 4-week evaluation period. Unlike the results obtained with UAMS-
1, rabbits infected with the heavily encapsulated Staphylococcus aureu
s strain Smith diffuse exhibited little evidence of disease even when
infected with 2 x 10(6) colony-forming units. The reduced virulence of
strain Smith diffuse was surprising given its greatly enhanced virule
nce (relative to UAMS-1) in a murine peritonitis model of staphylococc
al disease. These results suggest that UAMS-1 expresses virulence fact
ors that are important in the pathogenesis of osteomyelitis and that s
ome or all of these virulence factors are either absent or are nut exp
ressed in strain Smith diffuse, Most importantly the results suggest t
hat our model may be appropriate for the identification and characteri
zation of these virulence factors.