The correct answer is A. invades intestinal mucosa without causing diarrhea.
Salmonella typhi is responsible for typhoid fever and primarily invades the intestinal mucosa and then disseminates throughout the body, typically resulting in systemic infection without the profuse diarrhea that is characteristic of non-typhoidal salmonella infections. Non-typhoidal salmonella typically causes gastroenteritis and is associated with diarrhea.
To clarify the other options: B. Salmonella typhi is not primarily zoonotic; it's primarily transmitted through contaminated food or water, while non-typhoidal salmonella is often zoonotic, transmitted from animals. C. Both forms of Salmonella have endotoxins; this option is incorrect. D. While Salmonella can invade epithelial cells, the description “only epithelial cells” is misleading as Salmonella can also invade other types of cells.
Thus, option A is the best choice.