Prosthetic Joint Infection Caused by Tropheryma whippelii (Whipple's Bacillus)

Whipple's disease is a systemic infection usually characterized by fever, weight loss, diarrhea, and polyarthritis. Attempts to culture the causative organism have been unsuccessful, but microscopic examination of infected tissue with periodic acid-Schiff (PAS) stain reveals infiltration by large macrophages that contain diastase-resistant inclusions. The causative agent of this systemic illness has recently been identified. A hitherto unknown bacterial 16S rRNA sequence was detected in bacterial DNA extracted from biopsy specimens from six patients. Detection of this sequence allowed specific identification of Whipple's disease and its proposed causative bacillus, Tropheryma whippelii. This bacterium has been suggested as belonging to the actinobacteria suprageneric group. We report a case of prosthetic knee joint infection due to T. whippelii. The patient had received a 20-month course of antibiotics 2 years previously, and she had been considered cured of Whipple's disease. The relapse was limited to her knee, which required replacement. The diagnosis was made with use of PCR, which detected a 16S rRNA gene in the articular fluid. To our knowledge, this is the first reported case of a prosthetic joint infection due to T. whippelii, and it illustrates the utility of PCR when diagnosis is suspected.