I am one of the most virulent foodborne pathogens, and widely recognized as an important hazard in the food industry. I am gram positive, rod-shaped, non-spore forming and motile. I cause more deaths than either Salmonella or Clostridium botulinum.
I was first discovered by E.G.D Murray in 1926, based on six cases of sudden death in young rabbits. He gave me my original name, Bacterium Monocytogenes. In 1940, I was given my current name by J.H. Harvey Pirie. I am named after an English surgeon who promoted the idea of sterile surgery while working at the Glasgow Royal Infirmary. He successfully introduced carbolic acid to sterilize surgical instruments and to clean wounds. Between the 1920’s and the 1950’s clinical descriptions of my existence were recorded, although it was not until after 1952 that I was recognized as a cause of neonatal sepsis and meningitis.
Thirty years later, I was accused of causing a foodborne illness. In Halifax, Nova Scotia, I was found in coleslaw that contained cabbage treated with contaminated raw sheep manure. In an outbreak that involved over 100 people, 34 of the infections involved pregnant women, nine stillbirths, 23 infants born infected, and two healthy births. Out of the 77 non-pregnant adults who developed overt disease, there was approximately 30% mortality. In 2002, an outbreak in the United States resulted in 46 culture confirmed cases, 7 deaths, and three stillbirths or miscarriages. The outbreak was linked to eating sliced turkey meat which came from a poultry processing plant.
I can cause symptoms such as fever, fatigue, nausea, cramps, vomiting and diarrhea, encephalitis, septicemia, pneumonia, endocarditis, aortic aneurysm and hepatitis.
I need a mate who can be found in a variety of environments and can grow and reproduce under a multitude of conditions as I am able to. I can be found in the soil, ground water, raw milk, soft cheeses, such as brie and feta, undercooked seafood, coleslaw, and ready to eat foods, such as hot dogs and deli meats. I am also found in the intestines of mammals. Between 5-10% of the human population harbors me in the intestinal tract with no apparent symptoms of the disease which I cause.
Contamination of products can occur at processing plants due to surfaces which have not been properly disinfected, contact with employees’ aprons, shoes or dirty equipment. I have the ability to form biofilms which make it easy for me to survive. I love cool, damp environments which are common in food processing facilities. The area around drains and hoses are some of my favorite places to grow.
I can also grow and reproduce in refrigerated temperatures. Freezing will not kill me, although pasteurization can. Heating procedures are my enemy, and the temperatures used to prepare ready-to-eat processed meats should be sufficient to kill me.
I can cause severe illness since I can enter host cells by phagocytosis. While I am in the host cell, I can travel throughout the body while the defense mechanisms of my host cannot harm me. If I am ingested in contaminated food, I am taken up by enterocytes in the lining of the small intestine and multiply in the underlying cells. From there I travel to the liver in blood or lymph, where most of my relatives are killed by neutrophils. The surviving members of my family then multiply in hepatocytes and macrophages, traveling throughout the bloodstream, crossing into the brain and the placenta.
My popularity within the scientific community is growing. I am among the most highly researched and investigated foodborne pathogen in the United States, Canada, and many other countries. Fast, highly effective tests exist which can identify some of the members of my family. These tests use antibodies that signal their presence. However, no rapid, sensitive tests have been available for detecting me, the deadliest of my species, until recently. Scientists have developed a biosensor which uses heat shock proteins to detect my presence. The heat shock proteins are produced when the body is under stress. This test is faster and more sensitive at detecting me than the old antibiotic tests, which may mean my way of life is in danger.
Who am I?
I am listeria monocytogenes
Kingdom: bacteria
Phylum: firmicutes
Class: bacilli
Order: bacillales
Family: listeriaceae
Genus: listeria
Species: listeria monocytogenes
(I was named after Joseph Lister)
I hope you had fun with this one, I sure did!
Cited References
Bad bug book: foodborne pathogenic microorganism and natural toxins handbook, listeria monocytogenes [online article]. In: United states food and drug administration. c2009 [cited 2009 November 12]. Available from: http://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm070064.htm.
Pathogens and contaminants: listeria monocytogenes [online article]. In: Food safety research information online. United states department of agriculture. c2009 [cited 2009 November 12]. Available from: http://fsrio.nal.usda.gov/document_fsheet.php?product_id=156.
Todar, Kenneth. Listeria monocytogenes. Todar’s online textbook of bacteriology. c2008 [cited 2009 November 11]. Available from: http://www.textbookofbacteriology.net/Listeria.html.
Virulence characteristics of listeria monocytogenes [online article]. In: Food research institute , university of wisconsin. c2008 [cited 2009 November 12]. Available from: http://www.pork.org/PorkScience/Research/Documents/98-162-DOYLE-Listeria.pdf.
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