Listeria monocytogenes Essay -- Essays Papers

Listeria monocytogenes Introduction Listeria monocytogenes, a motile, gram-positive rod, is an opportunistic food-borne pathogen capable of causing listeriosis in humans. Listeriosis includes manifestations of septicemia, meningitis, pneumonia, and encephalitis. L. monocytogenes is also implicated in miscarriages, stillbirth, and premature birth for pregnant women. L. monocytogenes is a tough bacterium resistant to freezing, drying, and heat; most strains have been shown to be pathogenic. It is hypothesized that 1-10% of humans are intestinal carriers of L. monocytogenes. Over 37 mammalian species, including wild and domestic animals, are capable of L. monocytogenes infection and transmission. Extensive environmental reservoirs for L. monocytogenes include soil, water, vegetation, sewage, silage, and the intestinal tract of various animals. Encounter: L. monocytogenes is transmitted by ingestion of contaminated food or water. The bacterium is associated with raw milk, cheeses, (particularly soft varieties) ice cream, raw vegetables, fermented raw-meat sausages, raw and cooked poultry, raw meats, and raw and smoked fish. It is capable of growing at temperatures as low as 3Â °C allowing multiplication in refrigerated foods, making L. monocytogenes infection particularly hard to avoid. The infective dose has not been determined, but is believed to vary with the susceptibility of the individual. It may be less than 1000 bacterium in the immuno-compromised individual. Entry, Multiplication, and Spread: L. monocytogenes initially gains access to the body through the gastrointestinal tract but is capable of infecting the blood through monocytes, macrophages and polymorphonuclear leukocytes. The bacterium is also capable of infe... ...s system involvement, the elderly and in persons with other serious medical problems. Worldwide: Approximately 2,500 cases of listeriosis are reported every year in the United States. This includes 500 preventable deaths. L. monocytogenes outbreaks are still occurring worldwide. Recently, in 2002 contaminated turkey deli meat caused a US outbreak 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, lunchmeats, and cheese. A California outbreak in 1985 was due to contaminated Mexican-style cheese. This outbreak led to numerous stillbirths resulting in the monitoring of cheeses by the FDA. Fortunately, according to a study done by The US Department of Health and Human Services, infections with L. monocytogenes have decreased 35 % from 1996 to 2002.