Whipple's disease is an infectious illness associated with a wide variety of intestinal and extraintestinal manifestations. Since untreated disease leads to death and because adequate antimicrobial therapy for diseases with similar clinical presentations differs significantly in the duration and choice of drugs, a reliable laboratory diagnosis is of considerable interest. The causative agent has been propagated in human macrophages deactivated with interleukin-4, but stable subcultures have been established only very recently. Based on its 16S ribosomal DNA (rDNA) sequence, it was classified as a member of the gram-positive bacteria with high G+C content and named Tropheryma whipplei (formerly Tropheryma whippelii).
Recently, T. whipplei DNA has been found in duodenal biopsy tissue, gastric juice, and saliva specimens but not in dental stone, of patients without Whipple's disease.
Despite recent success in culturing T. whipplei, the clinical suspicion of Whipple's disease is usually confirmed by periodic acid-Schiff staining of inclusions in macrophages or by electron microscopy showing the characteristic trilamellar membrane of T. whipplei.
Molecular tests are significantly more sensitive than histopathology for intestinal and extraintestinal specimens. T. whipplei-specific seminested PCR utilizes a 500-bp segment of the hsp65 gene for the specific detection of T. whipplei.
La Scola et al. 51 (4):(2001) Description of Tropheryma whipplei gen. nov., sp. nov., the Whipple’s disease bacillus in International Journal of Systematic and Evolutionary Microbiology, pp1471–1479