Pathology and biofilm formation in a porcine model of staphylococcal osteomyelitis.

A porcine model was used to examine the potential of human and porcine Staphylococcus aureus isolates to induce haematogenously spread osteomyelitis. Pigs were inoculated in the right femoral artery with one of the following S. aureus strains: S54F9 (from a porcine lung abscess; n = 3 animals), NCTC-8325-4 (a laboratory strain of human origin; n = 3 animals) and UAMS-1 (a human osteomyelitis isolate; n = 3 animals). Two pigs were sham inoculated with saline. At 11 or 15 days post infection the animals were scanned by computed tomography before being killed and subjected to necropsy examination. Osteomyelitis lesions were present in the right hind limb of all pigs inoculated with strain S54F9 and in one pig inoculated with strain NCTC-8325-4. Microscopically, there was extensive loss of bone tissue with surrounding granulation tissue. Sequestrated bone trabeculae were intermingled with colonies of S. aureus as demonstrated immunohistochemically. By peptide nucleic acid fluorescence in situ hybridization bacterial aggregates were demonstrated to be embedded in an opaque matrix, indicating that the bacteria had formed a biofilm. Development of experimental osteomyelitis was therefore dependent on the strain of bacteria inoculated and on the formation of a biofilm.

Dual-energy X-ray absorptiometry of the pig: Protocol development and evaluation.

As part of a prospective study in bone mineralisation in adult pigs it was necessary to establish guidelines and to define sites for bone mineral measurements. Particular requirements were that, the protocol should be suitable for a mass screening programme in both postmortem specimens and in live animals, and should deliver results of known reliability. Estimates of bone mineral content (BMC) and bone mineral density (BMD) in areas within the 4th metacarpal bone yielded coefficients of variation (CV) in the order of 7% for both regions and estimates in regions which included the entire metacarpal-phalangeal area yielded CV values in the order of 0.7% and 0.6% for BMC and BMD, respectively. A region of interest taken from the coccygeal vertebrae yielded coefficient of variation values of 3% and 2% for BMC and BMD, respectively. Accuracy of dual-energy X-ray absorptiometry (DXA) was estimated using a standard curve derived from BMC determined by ashing. There was a high correlation between mineral content determined by DXA and by ashing (R(2)=0.99, p<0.0001). The results suggest that the regions used in this study are suitable for use in large, mass screening, prospective studies.