Rabbit anti-Listeriolysin O Affinity Purified polyclonal antibody for IP, WB, ELISA. Listeria monocytogenes, a facultative anaerobe, intracellular bacterium, is 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. Responsible for approximately 2,500 illnesses and 500 deaths in the United States (U.S.) annually, listeriosis is the leading cause of death among foodborne bacterial pathogens, with fatality rates exceeding even Salmonella and Clostridium botulinum.