What is the specific agent of Listeriosis?

Listeriosis is specifically caused by the bacterium Listeria monocytogenes. This organism is a pathogen that can lead to severe illness, particularly in vulnerable populations such as pregnant women, newborns, the elderly, and individuals with weakened immune systems. Listeria monocytogenes is unique in its ability to grow in a wide range of temperatures, including refrigeration, which makes it particularly concerning in food safety, especially in ready-to-eat foods.

In contrast, the other choices represent different pathogens associated with different diseases. Clostridium botulinum is known for causing botulism, a serious illness that results from a toxin produced by the bacterium. Salmonella typhi causes typhoid fever, an infectious disease distinct from listeriosis. Yersinia pestis is the causative agent of the plague, which is also unrelated to Listeria monocytogenes and its associated conditions. Understanding these distinctions reinforces the critical role that Listeria monocytogenes plays in food safety and public health.