Light micrograph (LM) showing Listeria monocytogenes, the causative agent of Listeriosis. It is one of the most virulent foodborne pathogens, with 20 to 30 percent of clinical infections resulting in death. Listeriosis is the leading cause of death among foodborne bacterial pathogens with fatality rates exceeding even Salmonella and Clostridium botulinum. Magnification: 400x at 35mm.