Which of the following is a Salmonella virulence factor?

• A. Adhesins
• B. Flagella
• C. Type III secretion system
• D. LPS

Answer: (C)

Salmonella relies on a specialized protein-delivery system that directly manipulates host cells, which is a hallmark of its virulence. The Type III secretion system acts like a molecular syringe encoded by Salmonella pathogenicity islands, delivering effector proteins into host cells. These effectors prompt rearrangement of the actin cytoskeleton to promote bacterial uptake, alter vesicle trafficking, and modulate immune responses to favor survival inside the host. This direct, active means of subverting host cell processes is a defining virulence mechanism in Salmonella, making the Type III secretion system the best answer. Adhesins help with attachment, flagella aid motility, and LPS contributes to immune activation and barrier disruption, but they don’t enact the targeted host-cell manipulation that this secretion system provides.