L. monocytogenes causes a variety of diseases, including food poisoning. Listeriae are small, Gram-positive, motile rod-shaped bacteria. Which of the following best describes these microorganisms?

Listeria multiply both extracellularly and intracellularly, but under most circumstances a competent immune system eliminates Listeria. As expected, listeriosis is seen in the very young, the very old, and in people with compromised immune systems. Repos of Listeria food outbreaks have implicated such foods like milk products.