Describe the sequence for systemic Salmonella disease progression.

Describe the sequence for systemic Salmonella disease progression.

• A. Adhere to intestinal lining > invade and replicate in M cells > escape and uptake into macrophages > intracellular replication (macrophage) > delivered to LN > enter blood > filtered in liver and spleen
• B. Adhere to intestinal lining and remain within epithelial cells
• C. Directly enter the bloodstream from the gut without macrophage involvement
• D. Invade the mucosa and cause local ulceration without systemic spread

Answer: (A)

The sequence being tested shows how Salmonella moves from the gut to a systemic infection. First, the bacteria adhere to the intestinal lining and then invade via specialized cells called M cells in the Peyer’s patches. From there they escape into underlying tissue and are taken up by macrophages, where Salmonella can survive and replicate inside the macrophage’s intracellular compartment. These infected macrophages carry the bacteria to the draining lymph nodes, from which the organisms spill into the bloodstream. Once in the blood, the bacteria circulate and are filtered by organs like the liver and spleen, where they can multiply and cause systemic disease such as typhoid fever. This path explains why systemic Salmonella disease occurs: the key step is survival and replication within macrophages that ferry the bacteria to lymph nodes and through the blood to distant organs. The other scenarios describe only local intestinal involvement or direct bloodstream entry without the macrophage-mediated route, which wouldn’t account for the observed systemic spread.

The sequence being tested shows how Salmonella moves from the gut to a systemic infection. First, the bacteria adhere to the intestinal lining and then invade via specialized cells called M cells in the Peyer’s patches. From there they escape into underlying tissue and are taken up by macrophages, where Salmonella can survive and replicate inside the macrophage’s intracellular compartment. These infected macrophages carry the bacteria to the draining lymph nodes, from which the organisms spill into the bloodstream. Once in the blood, the bacteria circulate and are filtered by organs like the liver and spleen, where they can multiply and cause systemic disease such as typhoid fever.

This path explains why systemic Salmonella disease occurs: the key step is survival and replication within macrophages that ferry the bacteria to lymph nodes and through the blood to distant organs. The other scenarios describe only local intestinal involvement or direct bloodstream entry without the macrophage-mediated route, which wouldn’t account for the observed systemic spread.