Listeriosis
Encyclopedia
Listeriosis is a bacterial infection caused by a Gram-positive
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...

, motile
Motility
Motility is a biological term which refers to the ability to move spontaneously and actively, consuming energy in the process. Most animals are motile but the term applies to single-celled and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in...

 bacterium, Listeria monocytogenes. Listeriosis is relatively rare and occurs primarily in newborn infants, elderly patients, and patients who are immunocompromised.

The symptoms of listeriosis usually last 7–10 days, with the most common symptoms being fever, muscle aches, and vomiting. Diarrhea is another, but less common symptom. If the infection spreads to the nervous system it can cause meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...

, an infection of the covering of the brain and spinal cord. Symptoms of meningitis are headache, stiff neck, confusion, loss of balance, and convulsions.

Listeriosis has a very low incidence in humans. However, pregnant women are much more likely than the rest of the population to contract it. Infected pregnant women may have only mild, flulike symptoms. However, infection in a pregnant woman can lead to early delivery, infection of the newborn, and death of the baby. It seems that Listeria originally evolved to invade membranes of the intestines, as an intracellular infection, and developed a chemical mechanism to do so. This involves a bacterial protein " internalin" which attaches to a protein on the intestinal cell membrane " cadherin." These adhesion molecules are also to be found in two other unusually tough barriers in humans - the blood brain barrier and the feto - placental barrier, and this may explain the apparent affinity that Listeria has for causing meningitis and affecting babies in-utero.

In veterinary medicine, listeriosis can be a quite common condition in some farm outbreaks. It can also be found in wild animals; see listeriosis in animals.

Signs and symptoms

The disease primarily affects older adults, persons with weakened immune systems, pregnant women, and newborns. Rarely, persons without these risk factors can also be affected. A person with listeriosis usually has fever and muscle aches, often preceded by diarrhea or other gastrointestinal symptoms. Almost everyone who is diagnosed with listeriosis has invasive infection (meaning that the bacteria spread from their intestines to their blood stream or other body sites). Disease may occur as much as two months after eating contaminated food.

The symptoms vary with the infected person:
  • High-risk persons other than pregnant women: Symptoms can include fever, muscle aches, headache, stiff neck, confusion, loss of balance, and convulsions.
  • Pregnant women: Pregnant women typically experience only a mild, flu-like illness. However, infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.
  • Previously healthy persons: People who were previously healthy but were exposed to a very large dose of Listeria can develop a non-invasive illness (meaning that the bacteria have not spread into their blood stream or other body sites). Symptoms can include diarrhea and fever.


If a person has eaten food contaminated with Listeria and does not have any symptoms, most experts believe that no tests or treatment are needed, even for persons at high risk for listeriosis.

Cause

Listeria monocytogenes is ubiquitous in the environment. The main route of acquisition of Listeria is through the ingestion of contaminated food products. Listeria has been isolated from raw meat, dairy products, vegetables, fruit and seafood
Seafood
Seafood is any form of marine life regarded as food by humans. Seafoods include fish, molluscs , crustaceans , echinoderms . Edible sea plants, such as some seaweeds and microalgae, are also seafood, and are widely eaten around the world, especially in Asia...

. Soft cheeses, unpasteurized milk and unpasteurised pâté
Pâté
Pâté is a mixture of ground meat and fat minced into a spreadable paste. Common additions include vegetables, herbs, spices, and either wine or cognac, armagnac or brandy...

 are potential dangers; however, some outbreaks involving post-pasteurized
Pasteurization
Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...

 milk have been reported.

Rarely listeriosis may present as cutaneous listeriosis. This infection occurs after direct exposure to L. monocytogenes by intact skin and is largely confined to veterinarians who are handling diseased animals, most often after a listerial abortion.

Diagnosis

In CNS
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 infection cases, L. monocytogenes can often be cultured from the blood, and always cultured from the CSF
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...

. There are no reliable serological or stool tests.

Prevention

The main means of prevention is through the promotion of safe handling, cooking and consumption of food. This includes washing raw vegetables and cooking raw food thoroughly, as well as reheating leftover or ready-to-eat foods like hot dogs until steaming hot.

Another aspect of prevention is advising high-risk groups such as pregnant women and immunocompromised patients to avoid unpasteurized pâtés and foods such as soft cheeses like feta
Feta
Feta is a brined curd cheese traditionally made in Greece. Feta is an aged crumbly cheese, commonly produced in blocks, and has a slightly grainy texture. It is used as a table cheese, as well as in salads Feta is a brined curd cheese traditionally made in Greece. Feta is an aged crumbly cheese,...

, Brie, Camembert cheese
Camembert (cheese)
Camembert is a soft, creamy, surface-ripened cow's milk cheese. It was first made in the late 18th century in Normandy in northern France.-Production:...

, and bleu. Cream cheese
Cream cheese
Cream cheese is a soft, mild-tasting, white cheese with a high fat content. Traditionally, it is made from unskimmed milk enriched with additional cream....

s, yogurt, and cottage cheese
Cottage cheese
Cottage cheese is a cheese curd product with a mild flavor. It is drained, but not pressed, so some whey remains and the individual curds remain loose. The curd is usually washed to remove acidity, giving sweet curd cheese. It is not aged or colored. Different styles of cottage cheese are made from...

 are considered safe. In the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, advice along these lines from the Chief Medical Officer posted in maternity clinics led to a sharp decline in cases of listeriosis in pregnancy in the late 1980s.

Treatment

Bacteremia
Bacteremia
Bacteremia is the presence of bacteria in the blood. The blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal....

 should be treated for 2 weeks, meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...

 for 3 weeks, and brain abscess
Brain abscess
Brain abscess is an abscess caused by inflammation and collection of infected material, coming from local or remote infectious sources, within the brain tissue...

 for at least 6 weeks. Ampicillin
Ampicillin
Ampicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections since 1961. Until the introduction of ampicillin by the British company Beecham, penicillin therapies had only been effective against Gram-positive organisms such as staphylococci and streptococci...

 generally is considered antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 of choice; gentamicin
Gentamicin
Gentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms. However, gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila...

 is added frequently for its synergistic effects. Overall mortality rate is 20–30%; of all pregnancy-related cases, 22% resulted in fetal loss or neonatal death, but mothers usually survive..

Epidemiology

Incidence in 2004–2005 was 2.5–3 cases per million population a year in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, where pregnant women accounted for 30% of all cases. Of all nonperinatal infections, 70% occur in immunocompromised patients. Incidence in the U.S. has been falling since the 1990s, in contrast to Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 where changes in eating habits have led to an increase during the same time. In Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, it has stabilized at around 5 cases per annum per million population, with pregnant women typically accounting for 1–2 of some 40 total yearly cases.

There are four distinct clinical syndromes:
  • Infection in pregnancy: Listeria can proliferate asymptomatically in the vagina
    Vagina
    The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

     and uterus
    Uterus
    The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...

    . If the mother becomes symptomatic, it is usually in the third trimester. Symptoms include fever
    Fever
    Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...

    , myalgia
    Myalgia
    Myalgia means "muscle pain" and is a symptom of many diseases and disorders. The most common causes are the overuse or over-stretching of a muscle or group of muscles. Myalgia without a traumatic history is often due to viral infections...

    s, arthralgias and headache
    Headache
    A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...

    . Miscarriage
    Miscarriage
    Miscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation...

    , stillbirth and preterm labor are complications of this infection. Symptoms last 7–10 days.
  • Neonatal infection (granulomatosis infantisepticum): There are two forms. One, an early-onset sepsis
    Sepsis
    Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...

    , with Listeria acquired in utero
    In utero
    In utero is a Latin term literally meaning "in the womb". In biology, the phrase describes the state of an embryo or fetus. In legal contexts, the phrase is used to refer to unborn children. Under common law, unborn children are still considered to exist for property transfer purposes.-See also:*...

    , results in premature birth. Listeria can be isolated in the placenta
    Placenta
    The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

    , blood
    Blood
    Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

    , meconium
    Meconium
    Meconium is the earliest stools of an infant. Unlike later feces, meconium is composed of materials ingested during the time the infant spends in the uterus: intestinal epithelial cells, lanugo, mucus, amniotic fluid, bile, and water. Meconium is almost sterile, unlike later feces, is viscous and...

    , nose
    Human nose
    The visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils...

    , ear
    Ear
    The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....

    s, and throat
    Throat
    In vertebrate anatomy, the throat is the anterior part of the neck, in front of the vertebral column. It consists of the pharynx and larynx...

    . Another, late-onset meningitis is acquired through vaginal transmission, although it also has been reported with caesarean deliveries.
  • Central nervous system
    Central nervous system
    The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

     (CNS) infection: Listeria has a predilection for the brain parenchyma
    Parenchyma
    Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...

    , especially the brain stem
    Brain stem
    In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...

    , and the meninges
    Meninges
    The meninges is the system of membranes which envelopes the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.-Dura...

    . It can cause cranial nerve palsies, encephalitis
    Encephalitis
    Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...

    , meningitis
    Meningitis
    Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...

    , meningoencephalitis
    Meningoencephalitis
    Meningoencephalitis is a medical condition that simultaneously resembles both meningitis, which is an infection or inflammation of the meninges, and encephalitis, which is an infection or inflammation of the brain.-Causes:...

     and abscess
    Abscess
    An abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...

    es. Mental status changes are common. Seizures occur in at least 25% of patients.
  • Gastroenteritis
    Gastroenteritis
    Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...

    : L. monocytogenes can produce food-borne diarrheal disease, which typically is noninvasive. The median incubation period is 21 days, with diarrhea lasting anywhere from 1–3 days. Patients present with fever, muscle aches, gastrointestinal nausea
    Nausea
    Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

     or diarrhea
    Diarrhea
    Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...

    , headache
    Headache
    A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...

    , stiff neck
    Meningism
    Meningism is the triad of nuchal rigidity , photophobia and headache. It is a sign of irritation of the meninges, such as seen in meningitis, subarachnoid hemorrhages and various other diseases...

    , confusion
    ConFusion
    ConFusion is an annual science fiction convention organized by the Stilyagi Air Corps and its parent organization, the Ann Arbor Science Fiction Association. Commonly, it is held the third weekend of January. It is the oldest science fiction convention in Michigan, a regional, general SF con...

    , loss of balance, or convulsions.


Particular strains of Listeria monocytogenes are able to invade the heart, leading to serious and difficult-to-treat heart infections. About 10 percent of serious listeria infections involve cardiac infections that are difficult to treat, with more than one-third proving fatal. A strain of listeria had been isolated from a patient with endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...

 (infection of the heart). Usually with endocarditis, there is bacterial growth on heart valves, but in this case the infection had invaded the cardiac muscle. When mice were infected with either the cardiac isolate or a lab strain, 10 times as much bacteria were found in the hearts of mice infected with the cardiac strain. In the spleen and liver, organs that are commonly targeted by listeria, the levels of bacteria were equal in both groups of mice. While the lab-strain-infected group often had no heart infection at all, 90 percent of the mice infected with the cardiac strain had heart infections. Only one other strain of listeria out of 10 acquired seemed to also target the heart. The results suggest that these two cardiac-associated strains display modified proteins on their surface that enable the bacteria to more easily enter cardiac cells, targeting the heart and leading to bacterial infection.

Recent outbreaks

According to the Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...

 (CDC) there are about 1,600 cases of listeriosis annually in the United States. Compared to 1996-1998, the incidence of listeriosis had declined by about 38% by 2003. However, illnesses and deaths continue to occur. On average from 1998-2008, 2.4 outbreaks per year were reported to the CDC. A large outbreak occurred in 2002, when 54 illnesses, 8 deaths, and 3 fetal deaths in 9 states were found to be associated with consumption of contaminated turkey deli meat.

The 2008 Canadian listeriosis outbreak
2008 Canadian listeriosis outbreak
The 2008 Canadian listeriosis outbreak was a widespread outbreak of listeriosis in Canada linked to cold cuts from a Maple Leaf Foods plant in Toronto, Ontario. 22 people died and there were 57 total confirmed cases.-Origin and spread:...

, a widespread outbreak of listeriosis in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 linked to a Maple Leaf Foods
Maple Leaf Foods
Maple Leaf Foods Inc. is a major Canadian food processing company, founded in 1927 as a merger of several major Toronto meat packers.-History:The company was originally known as Canada Packers...

 plant in Toronto
Toronto
Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...

, Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

 killed 23 people and there were 57 total confirmed cases.

On September 14, 2011, the U.S. Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

 warned consumers not to eat cantaloupe
Cantaloupe
"Rockmelon" redirects here, for the band see Rockmelons. See also Cantaloupe .Cantaloupe refers to a variety of Cucumis melo, a species in the family Cucurbitaceae which includes nearly all melons and squashes. Cantaloupes range in size from...

s shipped by Jensen Farms from Granada, Colorado due to a potential link to a multi-state outbreak of listeriosis. At that time Jensen Farms voluntarily recalled cantaloupes shipped from July 29 through September 10, and distributed to at least 17 states with possible further distribution. The CDC reported that at least 22 people in seven states had been infected as of September 14. On September 26, the Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...

 reported that a total of 72 persons had been infected with the four outbreak-associated strains of Listeria monocytogenes which had been reported to the CDC from 18 states. All illnesses started on or after July 31, 2011 and by September 26, thirteen deaths had been reported: 2 in Colorado, 1 in Kansas, 1 in Maryland, 1 in Missouri, 1 in Nebraska, 4 in New Mexico, 1 in Oklahoma, and 2 in Texas. On September 30, 2011, a random sample of romaine lettuce taken by the U.S. Food and Drug Administration tested positive for listeria on lettuce shipped on September 12 and 13 by an Oregon distributor to at least two other states -- Washington and Idaho.

By October 18, the CDC reported that 12 states are now linked to listeria in cantaloupe and that 123 people have been sickened and a total of 25 have died. While the tainted cantaloupes should be off store shelves by now, the number of illnesses may still continue to grow. The CDC confirmed a sixth death in Colorado and a second in New York; Indiana, Kansas, Louisiana, Maryland, Missouri, Nebraska, New Mexico, Oklahoma, Texas and Wyoming have also reported deaths.

See also

  • List of United States foodborne illness outbreaks
  • 2008 Canadian listeriosis outbreak
    2008 Canadian listeriosis outbreak
    The 2008 Canadian listeriosis outbreak was a widespread outbreak of listeriosis in Canada linked to cold cuts from a Maple Leaf Foods plant in Toronto, Ontario. 22 people died and there were 57 total confirmed cases.-Origin and spread:...


External links

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