Final answer:
Listeria monocytogenes is a gram-positive rod-shaped bacteria that causes listeriosis. It is transmitted through contaminated food and produces virulence factors that allow it to invade cells and spread in the body. Diagnostic tests for Listeria monocytogenes include gram staining, microscopy, and cultivation of samples from normally sterile sites.
Step-by-step explanation:
Listeria monocytogenes is a gram-positive rod-shaped bacteria that causes listeriosis. It is a foodborne pathogen that can be found in soil, water, and contaminated food. Listeria monocytogenes can be transmitted through the ingestion of contaminated food, particularly meat, fish, and dairy products. Surface proteins called internalins help the bacteria invade nonphagocytic cells and spread to different body systems. The bacteria also produce virulence factors like listeriolysin O and ActA, which facilitate intercellular movement and enable the infection to spread. Diagnostic tests for Listeria monocytogenes include gram staining, microscopy, and cultivation of samples from normally sterile sites like blood or cerebrospinal fluid. Pulsed-field gel electrophoresis is used to identify types and subtypes of the bacteria.