Classification Listeria monocytogenes & History
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Listeria monocytogenes is the species of pathogenic bacteria that
causes the infection listeriosis. It is a facultative anaerobic
bacterium, capable of surviving in the presence or absence of oxygen.
L. monocytogenes is a Gram-positive, nonspore-forming, motile, facultatively anaerobic, rod-shaped bacterium. It is catalase-positive and oxidase-negative, and expresses a beta hemolysin, which causes destruction of red blood cells. This bacterium exhibits characteristic tumbling motility when viewed with light microscopy. Although L. monocytogenes is actively motile by means of peritrichous flagella at room temperature (20−25°C), the organism does not synthesize flagella at body temperatures (37°C).
The genus Listeria belongs to the class, Bacilli, and the order, Bacillales, which also includes Bacillus and Staphylococcus. The genus Listeria includes seven different species (L. monocytogenes, L. ivanovii, L. innocua, L. welshimeri, L. seeligeri, L. grayi, and L. murrayi). Both L. ivanovii and L. monocytogenes are pathogenic in mice, but only L. monocytogenes is consistently associated with human illness. There are 13 serotypes of L. monocytogenes that can cause disease, but more than 90 percent of human isolates belong to only three serotypes: 1/2a, 1/2b, and 4b. L. monocytogenes serotype 4b strains are responsible for 33 to 50 percent of sporadic human cases worldwide and for all major foodborne outbreaks in Europe and North America since the 1980s.
L. monocytogenes was first described by E.G.D. Murray in 1926 based on six cases of sudden death in young rabbits. Murray referred to the organism as Bacterium monocytogenes before J.H. Harvey Pirie changed the genus name to Listeria in 1940. Although clinical descriptions of L. monocytogenes infection in both animals and humans were published in the 1920s, not until 1952 in East Germany was it recognized as a significant cause of neonatal sepsis and meningitis. Listeriosis in adults would later be associated with patients living with compromised immune systems, such as individuals taking immunosuppressant drugs and corticosteroids for malignancies or organ transplants, and those with HIV infection.
Not until 1981, however, was L. monocytogenes identified as a cause of foodborne illness. An outbreak of listeriosis in Halifax, Nova Scotia involving 41 cases and 18 deaths, mostly in pregnant women and neonates, was epidemiologically linked to the consumption of coleslaw containing cabbage that had been treated with L. monocytogenes-contaminated raw sheep manure. Since then, a number of cases of foodborne listeriosis have been reported, and L. monocytogenes is now widely recognized as an important hazard in the food industry
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What is Listeria monocytogenes in food?
Listeria is the name of a bacteria
found in soil and water and some animals, including poultry and cattle.
It can be present in raw milk and foods made from raw milk. It can also
live in food processing plants and contaminate a variety of processed
meats.
What are the symptoms of listeriosis?
The symptoms of listeriosis include fever, muscle aches, and sometimes nausea or diarrhea.
If infection spreads to the nervous system, symptoms such as headache,
stiff neck, confusion, loss of balance, or convulsions can occur. But
infected pregnant women may experience only a mild, flu-like illness.
What are the effects of listeriosis?
Listeria infection is a foodborne bacterial illness that can be very serious for pregnant women and people with impaired immune systems. Listeria infection is most commonly contracted by eating improperly processed deli meats and unpasteurized milk products.
What is the cause of listeria?
Causes. Listeria
bacteria can be found in soil, water and animal feces. Humans typically
are infected by consuming: Raw vegetables that have been contaminated
from the soil or from contaminated manure used as fertilizer.
L. monocytogenes is a Gram-positive, nonspore-forming, motile, facultatively anaerobic, rod-shaped bacterium. It is catalase-positive and oxidase-negative, and expresses a beta hemolysin, which causes destruction of red blood cells. This bacterium exhibits characteristic tumbling motility when viewed with light microscopy. Although L. monocytogenes is actively motile by means of peritrichous flagella at room temperature (20−25°C), the organism does not synthesize flagella at body temperatures (37°C).
The genus Listeria belongs to the class, Bacilli, and the order, Bacillales, which also includes Bacillus and Staphylococcus. The genus Listeria includes seven different species (L. monocytogenes, L. ivanovii, L. innocua, L. welshimeri, L. seeligeri, L. grayi, and L. murrayi). Both L. ivanovii and L. monocytogenes are pathogenic in mice, but only L. monocytogenes is consistently associated with human illness. There are 13 serotypes of L. monocytogenes that can cause disease, but more than 90 percent of human isolates belong to only three serotypes: 1/2a, 1/2b, and 4b. L. monocytogenes serotype 4b strains are responsible for 33 to 50 percent of sporadic human cases worldwide and for all major foodborne outbreaks in Europe and North America since the 1980s.
L. monocytogenes was first described by E.G.D. Murray in 1926 based on six cases of sudden death in young rabbits. Murray referred to the organism as Bacterium monocytogenes before J.H. Harvey Pirie changed the genus name to Listeria in 1940. Although clinical descriptions of L. monocytogenes infection in both animals and humans were published in the 1920s, not until 1952 in East Germany was it recognized as a significant cause of neonatal sepsis and meningitis. Listeriosis in adults would later be associated with patients living with compromised immune systems, such as individuals taking immunosuppressant drugs and corticosteroids for malignancies or organ transplants, and those with HIV infection.
Not until 1981, however, was L. monocytogenes identified as a cause of foodborne illness. An outbreak of listeriosis in Halifax, Nova Scotia involving 41 cases and 18 deaths, mostly in pregnant women and neonates, was epidemiologically linked to the consumption of coleslaw containing cabbage that had been treated with L. monocytogenes-contaminated raw sheep manure. Since then, a number of cases of foodborne listeriosis have been reported, and L. monocytogenes is now widely recognized as an important hazard in the food industry
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