Listeria monocytogenesIntroductionListeria monocytogenes, a Gram-positive motile rod, is a foodborne opportunistic pathogen capable of causing listeriosis in humans. Listeriosis includes manifestations of sepsis, meningitis, pneumonia and encephalitis. L. monocytogenes is also implicated in miscarriages, stillbirths and premature births in pregnant women. L. monocytogenes is a robust bacteria that resists freezing, drying and heat; most strains were found to be pathogenic. It is assumed that 1 to 10% of humans are intestinal carriers of L. monocytogenes. More than 37 species of mammals, including wild and domestic animals, are capable of infecting and transmitting L. monocytogenes. Large environmental reservoirs of L. monocytogenes include soil, water, vegetation, sewage, silage, and the intestinal tract of various animals. Encounter: L. monocytogenes is transmitted by ingestion of food or water contaminated. The bacteria is associated with raw milk, cheeses (especially soft varieties), ice cream, raw vegetables, fermented sausages made from raw meat, raw and cooked poultry, raw meats, and raw and smoked fish. . It is capable of growing at temperatures as low as 3°C, allowing it to multiply in refrigerated foods, making infection with L. monocytogenes particularly difficult to avoid. The infectious dose has not been determined, but is believed to vary depending on the susceptibility of the individual. There may be fewer than 1,000 bacteria in the immunocompromised individual. Entry, multiplication and spread: L. monocytogenes initially enters the body through the gastrointestinal tract, but is capable of infecting the bloodstream via monocytes, macrophages and polymorphonuclear leukocytes. The bacteria is also capable of infecting the paper system, the elderly and people with other serious medical conditions. Worldwide: Approximately 2,500 cases of listeriosis are reported each year in the United States. This includes 500 preventable deaths. Outbreaks of L. monocytogenes still occur worldwide. Most recently, in 2002, contaminated turkey deli meat caused an outbreak in the United States along the East Coast, and contaminated cheese caused an outbreak in British Columbia. Outbreaks over the past twenty years have involved contaminated chocolate milk, shrimp, cured meats and cheese. An outbreak in California in 1985 was due to contaminated Mexican-style cheese. This outbreak led to numerous stillbirths resulting in cheese surveillance by the FDA. Fortunately, according to a study by the U.S. Department of Health and Human Services, L. monocytogenes infections decreased by 35% between 1996 and 2002.