Campylobacter jejuni and related species are the leading bacterial cause of diarrheal disease in industrialized countries, though their molecular pathogenic mechanisms remain incompletely understood. This review examines campylobacter biology, clinical presentation, epidemiology, and pathogenesis. C. jejuni typically causes inflammatory diarrhea in developed nations, characterized by abdominal pain, bloody stools, and intestinal mucosal damage, while non-inflammatory watery diarrhea predominates in developing countries. The bacteria are primarily transmitted through contaminated food, particularly poultry, and unpasteurized milk. Key virulence factors include flagellar motility and chemotaxis for colonizing the intestinal mucus layer, adhesion mechanisms involving outer membrane proteins and newly discovered fimbriae, and the capacity for cellular invasion. The flagellum, the best-characterized virulence determinant, undergoes post-translational modifications including glycosylation and sialylation that may influence immune responses. Additional pathogenic mechanisms involve iron acquisition systems and oxidative stress resistance. The bacteria preferentially target intercellular junctions and can transcytose epithelial cell layers. Host factors, immune status, and strain-specific differences significantly influence disease severity and clinical manifestations.

Key findings

• C. jejuni is the leading bacterial cause of diarrhea in industrialized countries, transmitted primarily through contaminated poultry and other food sources
• The flagellum is essential for colonization and undergoes post-translational glycosylation and sialylation modifications that affect immune responses
• Newly identified fimbriae contribute to virulence and an aggregative phenotype, and their loss ameliorates disease symptoms in animal models
• Campylobacters invade intestinal epithelial cells preferentially at intercellular junctions and can transcytose polarized monolayers, with invasion efficiency depending on bacterial strain and host factors
• Iron acquisition and storage systems, including ferritin production, are important for colonization and protection against oxidative stress