Listeriosis
Listeriosis
Definition
Listeriosis is an illness caused by the bacterium Listeria monocytogenes that is acquired by eating contaminated food. The organism can spread to the blood stream and central nervous system. During pregnancy, listeriosis often causes miscarriage or stillbirth.
Description
Listeriosis is caused by an infection with the bacterium Listeria monocytogenes. This bacteria can be carried by many animals and birds, and it has been found in soil, water, sewage, and animal feed. Five out of every 100 people carry Listeria monocytogenes in their intestines. Listeriosis is considered a "food-borne illness" because most people are probably infected after eating food contaminated with Listeria monocytogenes. However, a woman can pass the bacteria to her baby during pregnancy. In addition, there have been a few cases where workers have developed Listeria skin infections by touching infected calves or poultry.
In the 1980s, the United States government began taking measures to decrease the occurrence of listeriosis. Processed meats and dairy products are now tested for the presence of Listeria monocytogenes. The Food and Drug Administration (FDA) and the Food Safety and Inspection Service (FSIS) can legally prevent food from being shipped, or order food recalls, if they detect any Listeria bacteria. These inspections, in combination with the public education regarding the proper handling of uncooked foods, appear to be working. In 1989, there were 1,965 cases of listeriosis with 481 deaths. In 1993, the numbers fell to 1,092 cases with 248 deaths.
In 1996, the Centers for Disease Control and Prevention (CDC) began a nationwide food-borne disease surveillance program called "FoodNet," in which seven states were participating by January 1997. Results from the program indicated that, in 1996, one person out of every 200,000 people got listeriosis. FoodNet also revealed that the hospitalization rate was higher for listeriosis (94%) than for any other food-borne illness. In addition, FoodNet found that the Listeria bacteria reached the blood and cerebrospinal fluid in 89% of cases, a higher percentage than in any other food-borne illness.
Persons at particular risk for listeriosis include the elderly, pregnant women, newborns, and those with a weakened immune system (called "immunocompromised"). Risk is increased when a person suffers from diseases such as AIDS, cancer, kidney disease, diabetes mellitus, or by the use of certain medications. Infection is most common in babies younger than one month old and adults over 60 years of age. Pregnant women account for 27% of the cases and immunocompromised persons account for almost 70%. Persons with AIDS are 280 times more likely to get listeriosis than others.
Causes and symptoms
As noted, persons become infected with Listeria monocytogenes by eating contaminated food. Listeria has been found on raw vegetables, fish, poultry, raw (unpasteurized) milk, fresh meat, processed meat (such as deli meat, hot dogs, and canned meat), and certain soft cheeses. Listeriosis outbreaks in the United States since the 1980s have been linked to cole slaw, milk, Mexican-style cheese, undercooked hot dogs, undercooked chicken, and delicatessen foods. Unlike most other bacteria, Listeria monocytogenes does not stop growing when food is in the refrigerator - its growth is merely slowed. Fortunately, typical cooking temperatures and the pasteurization process do kill this bacteria.
Listeria bacteria can pass through the wall of the intestines, and from there they can get into the blood stream. Once in the blood stream, they can be transported anywhere in the body, but are commonly found the central nervous system (brain and spinal cord); and in pregnant women they are often found in the placenta (the organ which connects the baby's umbilical cord to the uterus). Listeria monocytogenes live inside specific white blood cells called macrophages. Inside macrophages, the bacteria can hide from immune responses and become inaccessible to certain antibiotics. Listeria bacteria are capable of multiplying within macrophages, and then may spread to other macrophages.
After consuming food contaminated with this bacteria, symptoms of infection may appear anywhere from 11-70 days later. Most people do not get any noticeable symptoms. Scientists are unsure, but they believe that Listeria monocytogenes can cause upset stomach and intestinal problems just like other foodborne illnesses. Persons with listeriosis may develop flu-like symptoms such as fever, headache, nausea and vomiting, tiredness, and diarrhea.
Pregnant women experience a mild, flu-like illness with fever, muscle aches, upset stomach, and intestinal problems. They recover, but the infection can cause miscarriage, premature labor, early rupture of the birth sac, and stillbirth. Unfortunately, half of the newborns infected with Listeria will die from the illness.
There are two types of listeriosis in the newborn baby: early-onset disease and late-onset disease. Early-onset disease refers to a serious illness that is present at birth and usually causes the baby to be born prematurely. Babies infected during the pregnancy usually have a blood infection (sepsis ) and may have a serious, whole body infection called granulomatosis infantisepticum. When a full-term baby becomes infected with Listeria during childbirth, that situation is called late-onset disease. Commonly, symptoms of late-onset listeriosis appear about two weeks after birth. Babies with late-term disease typically have meningitis (inflammation of the brain and spinal tissues); yet they have a better chance of surviving than those with early-onset disease.
Immunocompromised adults are at risk for a serious infection of the blood stream and central nervous system (brain and spinal cord). Meningitis occurs in about half of the cases of adult listeriosis. Symptoms of listerial meningitis occur about four days after the flu-like symptoms and include fever, personality change, uncoordinated muscle movement, tremors, muscle contractions, seizures, and slipping in and out of consciousness.
Listeria monocytogenes causes endocarditis in about 7.5% of the cases. Endocarditis is an inflammation of heart tissue due to the bacterial infection. Listerial endocarditis causes death in about half of the patients. Other diseases which have been caused by Listeria monocytogenes include brain abscess, eye infection, hepatitis (liver disease), peritonitis (abdominal infection), lung infection, joint infection, arthritis, heart disease, bone infection, and gallbladder infection.
Diagnosis
Listeriosis may be diagnosed and treated by infectious disease specialists and internal medicine specialists. The diagnosis and treatment of this infection should be covered by most insurance providers.
The only way to diagnose listeriosis is to isolate Listeria monocytogenes from blood, cerebrospinal fluid, or stool. A sample of cerebrospinal fluid is removed from the spinal cord using a needle and syringe. This procedure is commonly called a spinal tap. The amniotic fluid (the fluid which bathes the unborn baby) may be tested in pregnant women with listeriosis. This sample is obtained by inserting a needle through the abdomen into the uterus and withdrawing fluid. Listeria grows well in laboratory media and test results can be available within a few days.
Treatment
Listeriosis is treated with the antibiotics ampicillin (Omnipen) or sulfamethoxazole-trimethoprim (Bactrim, Septra). Because the bacteria live within macrophage cells, treatment may be difficult and the treatment periods may vary. Usually, pregnant women are treated for two weeks; newborns, two to three weeks; adults with mild disease, two to four weeks; persons with meningitis, three weeks; persons with brain abscesses, six weeks; and persons with endocarditis, four to six weeks.
Patients are often hospitalized for treatment and monitoring. Other drugs may be provided to relieve pain and fever and to treat other reactions to the infection.
Prognosis
The overall death rate for listeriosis is 26%. This high death rate is due to the serious illness suffered by newborns, the elderly, and immunocompromised persons. Healthy adults and older children have a low death rate. Complications of Listeria infection include: meningitis, sepsis, miscarriage, stillbirth, pneumonia, shock, endocarditis, abscess (localized infection) formation, and eye inflammation.
Prevention
The United States government has already done much to prevent listeriosis. Persons at extremely high risk (pregnant women, immunocompromised persons, etc.) must use extra caution. High risk persons should: avoid soft cheeses, such as Mexican cheese, feta, Brie, Camembert, and blue cheese (cottage cheese is safe), thoroughly cook leftovers and ready-to-eat foods (such as hot-dogs), and avoid foods from the deli.
For all people, the risk of listeriosis can be reduced by taking these precautions:
- Completely cook all meats and eggs.
- Carefully wash raw vegetables before eating.
- Keep raw meat away from raw vegetables and prepared foods. After cutting raw meat, wash the cutting board with detergent before using it for vegetables.
- Avoid drinking unpasteurized milk or foods made from such milk.
- Wash hands thoroughly after handling raw meat.
- Follow the instructions on food labels. Observe food expiration dates and storage conditions.
Resources
OTHER
"Preventing Foodborne Illness: Listeriosis." Centers for Disease Control. 〈http://www.cdc.gov/ncidad/diseases/foodborn/lister.htm〉.
KEY TERMS
Abscess— An accumulation of pus caused by localized infection in tissues or organs. Listeria monocytogenes can cause abscesses in many organs including the brain, spleen, and liver.
Immunocompromised— To have a poor immune system due to disease or medication. Immunocompromised persons are at risk for developing infections because they can't fight off microorganisms like healthy persons can.
Macrophages— White blood cells whose job is to destroy invading microorganisms. Listeria monocytogenes avoids being killed and can multiply within the macrophage.
Meningitis— An inflammation of the tissues that surround the brain and spinal cord. It can be caused by a bacterial infection.
Sepsis— The presence of bacteria in the blood stream, a normally sterile environment.
Listeriosis
Listeriosis
Definition
Listeriosis is an illness caused by the bacterium Listeria monocytogenes that is acquired by eating contaminated food. The organism can spread to the blood stream and central nervous system. In women who contract listeriosis while pregnant, the disease often causes miscarriage or stillbirth.
Description
Listeriosis is caused by an infection with the bacterium Listeria monocytogenes. These bacteria can be carried by many animals and birds, and they have been found in soil, water, sewage, and animal feed. Five out of every 100 people carry Listeria monocytogenes in their intestines. Listeriosis is considered a food-borne illness because most people are probably infected after eating food contaminated with Listeria monocytogenes. However, a woman can pass the bacteria to her baby during pregnancy. In addition, there have been a few cases where workers have developed Listeria skin infections by touching infected calves or poultry.
In the 1980s, the United States government began taking measures to decrease the occurrence of listeriosis. Subsequently, processed meats and dairy products were tested for the presence of Listeria monocytogenes. The Food and Drug Administration (FDA) and the Food Safety and Inspection Service (FSIS) can legally prevent food from being shipped, or order food recalls, if they detect any Listeria bacteria. These inspections, in combination with the public education regarding the proper handling of uncooked foods, appear to be helping. Nonetheless, as of 2004, about 2,500 individuals become seriously ill from Listeria annually, with about 500 deaths.
Demographics
Persons at particular risk for listeriosis include the elderly, pregnant women, newborns, and those with a weakened immune system (called immunocompromised). Risk is increased when a person suffers from diseases such as AIDS , cancer , kidney disease, diabetes mellitus , or by the use of certain medications. Infection is most common in babies younger than one month old and adults over 60 years of age. Pregnant women account for 27 percent of the cases, and immunocompromised persons account for almost 70 percent. Persons with AIDS are 280 times more likely to get listeriosis than others.
Causes and symptoms
As noted, persons become infected with Listeria monocytogenes by eating contaminated food. Listeria has been found on raw vegetables, fish, poultry, raw (unpasteurized) milk, fresh meat, processed meat (such as deli meat, hot dogs, and canned meat), and certain soft cheeses. Listeriosis outbreaks in the United States since the 1980s have been linked to cole slaw, milk, Mexican-style cheese, undercooked hot dogs, undercooked chicken, and delicatessen foods. Unlike most other bacteria, Listeria monocytogenes does not stop growing when food is in the refrigerator; its growth is merely slowed. Fortunately, typical cooking temperatures and the pasteurization process do kill this bacteria.
Listeria bacteria can pass through the wall of the intestines, and from there they can get into the blood stream. Once in the blood stream, they can be transported anywhere in the body but are commonly found the central nervous system (brain and spinal cord); and in pregnant women they are often found in the placenta (the organ which connects the baby's umbilical cord to the uterus). Listeria monocytogenes live inside specific white blood cells called macrophages. Inside macrophages, the bacteria can hide from immune responses and become inaccessible to certain antibiotics . Listeria bacteria are capable of multiplying within macrophages and then may spread to other macrophages.
After people consume food contaminated with this bacteria, they may see symptoms of infection 11 to 70 days later. Most people do not get any noticeable symptoms. Scientists suspect that Listeria monocytogenes can cause upset stomach and intestinal problems just like other food-borne illnesses. Persons with listeriosis may develop flu-like symptoms such as fever , headache , nausea and vomiting , tiredness, and diarrhea .
Pregnant women experience a mild, flu-like illness with fever, muscle aches, upset stomach, and intestinal problems. They recover, but the infection can cause miscarriage, premature labor, early rupture of the birth sac, and stillbirth. Half of the newborns infected with Listeria die from the illness.
There are two types of listeriosis in the newborn baby: early-onset disease and late-onset disease. Earlyonset disease refers to a serious illness that is present at birth and usually causes the baby to be born prematurely. Babies infected during the pregnancy usually have a blood infection (sepsis) and may have a serious, whole body infection called granulomatosis infantisepticum. When a full-term baby becomes infected with Listeria during childbirth , that situation is called late-onset disease. Commonly, symptoms of late-onset listeriosis appear about two weeks after birth. Babies with late-term disease typically have meningitis (inflammation of the brain and spinal tissues); yet they have a better chance of surviving than those with early-onset disease.
Immunocompromised adults are at risk for a serious infection of the blood stream and central nervous system (brain and spinal cord). Meningitis occurs in about half of the cases of adult listeriosis. Symptoms of listerial meningitis occur about four days after the flu-like symptoms and include fever, personality change, uncoordinated muscle movement, tremors, muscle contractions, seizures, and slipping in and out of consciousness.
Listeria monocytogenes causes endocarditis in about 7.5 percent of the cases. Endocarditis is an inflammation of heart tissue due to the bacterial infection. Listerial endocarditis causes death in about half of the patients. Diseases which have been caused by Listeria monocytogenes include brain abscess, eye infection, hepatitis (liver disease), peritonitis (abdominal infection), lung infection, joint infection, arthritis, heart disease, bone infection, and gallbladder infection.
Diagnosis
Listeriosis may be diagnosed and treated by infectious disease specialists and internal medicine specialists. The diagnosis and treatment of this infection should be covered by most insurance providers.
The only way to diagnose listeriosis is to isolate Listeria monocytogenes from blood, cerebrospinal fluid, or stool. A sample of cerebrospinal fluid is removed from the spinal cord using a needle and syringe. This procedure is commonly called a spinal tap. The amniotic fluid (the fluid which bathes the unborn baby) may be tested in pregnant women with listeriosis. This sample is obtained by inserting a needle through the abdomen into the uterus and withdrawing fluid. Listeria grows well in laboratory media, and test results can be available within a few days.
Treatment
Listeriosis is treated with the antibiotics ampicillin (Omnipen) or sulfamethoxazole-trimethoprim (Bactrim, Septra). Because the bacteria live within macrophage cells, treatment may be difficult, and the treatment periods may vary. Usually, pregnant women are treated for two weeks; newborns, two to three weeks; adults with mild disease, two to four weeks; persons with meningitis, three weeks; persons with brain abscesses, six weeks; and persons with endocarditis, four to six weeks.
Patients are often hospitalized for treatment and monitoring. Other drugs may be provided to relieve pain and fever and to treat other reactions to the infection.
Prognosis
The overall death rate for listeriosis is 26 percent. This high death rate is due to the serious illness suffered by newborns, the elderly, and immunocompromised persons. Healthy adults and older children have a low death rate. Complications of Listeria infection include: meningitis, sepsis, miscarriage, stillbirth, pneumonia , shock endocarditis, abscess (localized infection) formation, and eye inflammation.
Prevention
As of the early 2000s the United States government has done much to prevent listeriosis. Persons at extremely high risk (pregnant women, immunocompromised persons, etc.) must use extra caution. High risk persons should avoid soft cheeses, such as Mexican cheese, feta, Brie, Camembert, and blue cheese (cottage cheese is safe); thoroughly cook leftovers and ready-to-eat foods (such as hot-dogs); and avoid foods from the deli.
For all people, the risk of listeriosis can be reduced by taking these precautions:
- Completely cook all meats and eggs.
- Carefully wash raw vegetables before eating.
- Keep raw meat away from raw vegetables and prepared foods. After cutting raw meat, wash the cutting board with detergent before using it for vegetables.
- Avoid drinking unpasteurized milk or foods made from such milk.
- Wash hands thoroughly after handling raw meat.
- Follow the instructions on food labels. Observe food expiration dates and storage conditions.
KEY TERMS
Abscess —A localized collection of pus in the skin or other body tissue caused by infection.
Immunocompromised —A state in which the immune system is suppressed or not functioning properly.
Macrophage —A large white blood cell that engulfs and digests foreign invaders, such as bacteria and viruses, in an attempt to stop them from causing disease within the body.
Meningitis —An infection or inflammation of the membranes that cover the brain and spinal cord. It is usually caused by bacteria or a virus.
Sepsis —A severe systemic infection in which bacteria have entered the bloodstream or body tissues.
Resources
BOOKS
Baltimore, Robert S. "Listeria monocytogenes. " In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004.
Lorber, Bennet. "Listeria monocytogenes. " In Principles and Practice of Pediatric Infectious Diseases, 2nd ed. Edited by Sarah S. Long et al. St. Louis, MO: Elsevier, 2003.
PERIODICALS
Goldenberg, R. L. "The infectious origins of stillbirth." American Journal of Obstetrics and Gynecology 189 September 2003): 861–873.
Ressel, G. W. "CDC Issues recommendations for diagnosing, managing, and reporting foodborne illnesses." American Family Physician 86 (September 2004): 981–985.
WEB SITES
"Listeriosis." Centers for Disease Control. Available online at <www.cdc.gov/ncidod/dbmd/diseaseinfo/listeriosis_g.htm#greatrisk> (accessed January 7, 2005).
Belinda Rowland, PhD Rosalyn Carson-DeWitt, MD
Listeriosis
Listeriosis
Disease History, Characteristics, and Transmission
Introduction
Listeriosis is an infection that is caused by eating food that is contaminated by the bacterium Listeria monocytogenes. The infection, which can be serious, primarily affects pregnant women, infants, and immunocompromised people (those whose immune systems are not functioning as efficiently as is normal).
Disease History, Characteristics, and Transmission
The bacterium Listera monocytogenes is a normal inhabitant of soil and water. Vegetables can become contaminated with the bacterium, if soil or manure clings to them. Humans can then become infected if the contaminated vegetables are not properly washed before eating.
Foods other than vegetables also can become contaminated, since animals, such as cattle, can harbor the bacterium without any ill effects. Meat and dairy products may become contaminated unknowingly. Infection can result, if the meat is eaten raw or is cooked improperly and if unpasteurized milk is consumed. Other foods that can be contaminated by L. monocytogenes include cheeses (particularly those made with unpasteurized milk) and processed meats that are unrefrigerated for a time sufficient for contaminating bacteria to multiply. In contrast to some bacterial infections, where a large number of living bacteria need to be consumed to cause illness, relatively few L. monocytogenes need to be eaten to cause listeriosis.
Symptoms of listeriosis include flulike fever, nausea, and vomiting, as well as abdominal cramping, diarrhea, and headache. The symptoms may appear within a few days after eating the contaminated foods, but also can appear 2–3 months later. In people whose immune systems are compromised, the infection can progress to a lethal blood infection (sepsis) or brain infection. Infections during pregnancy can lead to infection of the newborn, as well as to miscarriage, stillbirth, or premature birth.
WORDS TO KNOW
IMMUNOCOMPROMISED: A reduction of the ability of the immune system to recognize and respond to the presence of foreign material.
PASTEURIZE: To subject a substance to pasteurization, a process where fluids such as wine and milk are heated for a predetermined time at a temperature that is below the boiling point of the liquid. The treatment kills any microorganisms that are in the fluid but does not alter the taste, appearance, or nutritive value of the fluid.
SEPSIS: Sepsis refers to a bacterial infection in the bloodstream or body tissues. This is a very broad term covering the presence of many types of microscopic disease-causing organisms. Sepsis is also called bacteremia. Closely related terms include septicemia and septic syndrome. According to the Society of Critical Care Medicine, severe sepsis affects about 750,000 people in the United States each year. However, it is predicted to rapidly rise to one million people by 2010 due to the aging U.S. population. Over the decade of the 1990s, the incident rate of sepsis increased over 91%.
Scope and Distribution
Listeriosis has become a significant health threat. In the United States, for example, approximately 2,500 people are sickened with listeriosis each year. Of these, about 500 die, representing a mortality (death) rate of 20%.
Pregnant women are about 20 times more likely to acquire listeriosis than are other adults. In addition, immunocompromised individuals, who cannot as easily fight off infections, are susceptible to listeriosis. The proper functioning of the immune system may be impaired by certain diseases, including diabetes, cancer, kidney disease, and acquired immunodeficiency syndrome (AIDS, also cited as acquired immune deficiency syndrome), as well as by advanced age, and certain drugs, such as those taken by transplant patients to reduce the likelihood of transplant rejection. Listeriosis also can occur in individuals whose immune systems are functioning normally, but the infection is usually not nearly as serious.
Treatment and Prevention
L. monocytogenes is easily killed by pasteurization—a process during which a product is held at a certain temperature for a certain length of time to kill most bacteria without altering the chemistry or taste of the product. However, some foods can become contaminated after they have been processed, but before they are packaged for sale. Delicatessen-style meat and hot dogs are two common examples. The bacteria can remain alive and capable of causing infection during transport of the product to the supermarket, sale, and consumption.
A number of common-sense precautions can prevent listeriosis. Thoroughly cooking beef, pork, and poultry is sufficient to kill any L. monocytogenes that may contaminate the product. Washing vegetables removes bacteria. When storing food, uncooked meat should not be allowed to come into contact with vegetables, food that is already cooked, or prepared foods. All items used in the preparation of uncooked foods should be thoroughly washed before re-use to avoid transferring L. monocytogenes to other foodstuffs. While cheeses made from unpasteurized milk (such as Brie, Camembert, and feta) are preferred by some people, and the consumption of unpasteurized milk is sometimes advocated as a healthy alternative, there is a risk to these practices, since they increase the likelihood of exposure to the bacteria. Finally, prepared foods should be eaten promptly, since L. monocytogenes, in contrast to most other disease-causing bacteria, can slowly grow at temperatures above 39°F(4°C). A malfunctioning refrigerator can also create conditions in which the bacteria can grow.
IN CONTEXT: EFFECTIVE RULES AND REGULATIONS
Government agencies such as the U.S. Food and Drug Administration and the U. S. Department of Agriculture monitor food regularly in an attempt to reduce contamination of food by the Listeria bacterium and other infectious agents. Food monitoring and plant inspection are key monitoring and prevention tools, recalls can also be issued for contaminated or suspect food.
Impacts and Issues
Listeriosis can be a serious infection and, in the case of pregnant women, it can lead to miscarriage, stillbirth, premature delivery, or infection in the newborn. Although pregnant women in the United States are not routinely tested for infection with the bacteria that causes listeriosis, many health care providers recommend that pregnant women avoid consuming unpasteurized milk products and ready-to-eat deli-type meat products unless they are reheated until steaming hot.
From 1996–2002, the rate of listeriosis cases in the United States fell by 35%. This is attributed to aggressive sampling and testing programs by government meat inspectors, and education designed to raise awareness about the dangers of L. monocytogenes, especially among at-risk groups, such as pregnant women. In 2003, the U.S. Food Safety and Inspection Service established new regulations for scrutiny at plants that make or process ready-to-eat meat and poultry products. The rule also encourages plants to install new technologies to eliminate or reduce the growth of L. monocytogenes.
Researchers are working on “smart packaging” that may help reduce the sale and consumption of contaminated foods, such as deli meats. One type of this packaging incorporates molecules that recognize surface components of L. monocytogenes. These molecules are combined with other molecules that change color in the presence of the bacterium, and this color change can alert consumers that the product is contaminated.
See AlsoBacterial Disease; Food-borne Disease and Food Safety.
BIBLIOGRAPHY
Books
DiClaudio, Dennis. The Hypochondriac's Pocket Guide to Horrible Diseases You Probably Already Have. New York: Bloomsbury, 2005.
Rosaler, Maxine. Listeriosis (Epidemics). New York: Rosen Publishing Group, 2003.
Ryser, Elliot T., and Elmer H. Marth. Listeria, Listeriosis, and Food Safety. 3rd ed. Boca Raton: CRC, 2007.
Brian Hoyle