Bacterium
Tropheryma whipplei
Actinobacterium of PAS-positive Whipple disease
troh-FAIR-ih-muh WIP-lee-eye
High-yield clue
PAS-positive foamy macrophages packed into the duodenal lamina propria are the hallmark microscopy clue.
Overview
A Gram-positive, rod-shaped actinobacterium that is the agent of Whipple disease, a rare systemic infection with prominent gastrointestinal involvement. It is a classic teaching example of PAS-positive foamy macrophages in the small-bowel lamina propria.
Classification
- Gram-positive
- Rod
- Actinobacteria
- Intracellular
Lab & identification clues
- PAS-positive macrophages on duodenal biopsy vocabulary
- PCR confirmation on tissue/fluids concept
- Difficult to culture (fastidious)
- Silver-stain positive inclusions vocabulary
Associations
- Malabsorption and weight-loss study presentation
- Migratory arthralgia as an early feature
- Neurologic and cardiac involvement vocabulary
- Middle-aged men epidemiology
Commonly confused with
- Mycobacterium avium complex (also PAS-positive macrophages)
- Nocardia species
Your notes
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.