Bacillary characteristics in Whipple's disease: an electron microscopic study.

Area of Science:

• Microbiology
• Gastroenterology
• Pathology

Background:

• Whipple's disease is a rare systemic infection.
• The causative agent, Tropheryma whipplei, has been difficult to study due to challenges in in vitro culture.
• Understanding the pathogen's interaction with host tissues is crucial for diagnosis and treatment.

Purpose of the Study:

• To investigate the ultrastructural localization of Whipple bacilli within intestinal biopsies.
• To characterize the cellular tropism and invasion patterns of Tropheryma whipplei.
• To identify novel sites of bacillary presence and their implications for pathogenesis.

Main Methods:

• Extensive electron microscopic examination of 19 intestinal biopsies from 13 untreated Whipple's disease patients.
• Detailed morphological analysis of bacillary presence within various mucosal and submucosal compartments.
• Comparative analysis of bacillary invasion across different host cell types.

Main Results:

• Profuse bacilli were observed free in the lamina propria and within macrophages.
• Bacillary invasion was noted in intestinal epithelial cells (11 patients), lymphatic endothelium (4), capillary endothelium (3), polymorphonuclear leukocytes (5), and plasma cells (2).
• Novel findings include bacillary presence within smooth muscle (2), intraepithelial lymphocytes (1), and mast cells (1).

Conclusions:

• The Whipple bacillus (Tropheryma whipplei) exhibits characteristics of an intracellular pathogen.
• Its ability to survive within macrophages and invade diverse cell types contributes to the systemic nature of Whipple's disease.
• The unique outer membrane of the bacillus may explain difficulties in in vitro cultivation.