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
Frequently asked questions
What is Tropheryma whipplei?
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.
What is the Gram stain of Tropheryma whipplei?
Tropheryma whipplei is Gram positive.
What are the lab clues for Tropheryma whipplei?
Lab clues for Tropheryma whipplei include PAS-positive macrophages on duodenal biopsy vocabulary, PCR confirmation on tissue/fluids concept, Difficult to culture (fastidious), and Silver-stain positive inclusions vocabulary.
What is Tropheryma whipplei commonly confused with?
Tropheryma whipplei is commonly confused with Mycobacterium avium complex (also PAS-positive macrophages) and Nocardia species.
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.