You isolate a bacterial species that expresses bile-resistant enzymes and adhesins specific for intestinal epithelial glycoproteins. Which portal of entry is most likely to lead to disease by this bacterium, and why?

• A. Inhalation (nose or mouth) because bile resistance is irrelevant for lung colonization and intestinal adhesins will function identically on respiratory epithelium.
• B. Percutaneous entry through intact skin because skin microbes encounter bile during sebum production making bile resistance crucial for cutaneous survival.
• C. Conjunctival exposure (eye) because tears are rich in bile salts and the adhesins will preferentially attach to ocular mucins rather than intestinal glycoproteins.
• D. Oral ingestion (mouth) because bile resistance enables survival in the small intestine and adhesins bind intestinal epithelial receptors needed for colonization and disease.

Answer: (D)