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The article by Wysenbeek et al 1 provides intriguing insights to the 15 day rabbit Staphylococcus epidermidis infectious arthritis model. However, challenge must be made to their conclusion that injection of corticosteroids into the infected joint seems to be harmless, in the setting of infectious arthritis.
Several issues render this model unacceptable for establishing safety of intra-articular corticosteroids in the setting of infectious arthritis. Staphylococcus epidermidis has low infectivity and pathogenicity compared with most articular pathogens.2-4 If you were to consider use of intra-articular corticosteroids as rendering the patient equivalent to the immunosuppressed patient, reduction of synovitis and proteoglycan depletion might be of interest. Of course, use of corticosteroids might change the use of the injected joint, assessment of which probably would require additional controls.
The real question seems to be what happens to the joint after antibiotic (and intra-articular corticosteroid) treatment. Analysis two weeks, two months, and six months post-treatment would seem important to identify clinically important effects of intra-articular corticosteroids.
One technical question seems appropriate. How were the section sites selected? The blinding does not seem to have taken place until after the slides were prepared. More detail on the selection process might provide insights as to whether “prime sites” were selected or if the same exact cuts were made in all knees.
The study by Wysenbeek et al 1provides insights to effect of short-term intra-articular corticosteroids on a low pathogenicity/low infectivity form of infectious arthritis. It is unclear if their conclusion about corticosteroid safety can be extrapolated to organisms of high infectivity/pathogenicity and to clinically significant impact.
We thank Dr Rothschild for his remarks. The importance of Staphylococcus epidermidis in joint infections is in infected prostetic joints, where S epidermidis is more common than S aureus.1-1 1-2 We hypothesised that as a first step, it might be advisable to start the study with not the most virulent bacteria. As stated in the article, we believed that the lower virulence of S epidermidis might give us a better observation of corticosteroid effect. Further research should investigate additional bacterial strains. Our study was for 15 days. We agree, and stated in our paper, that future studies should investigate long term effect of this treatment. All joints of the various study groups were cut and prepared identically.
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