Listeriosis and Pregnancy

(Modified from original)

When you’re expecting, it’s natural to be concerned about your health and that of your unborn baby. Maintaining a healthful diet, drinking plenty of liquids, and taking prenatal vitamins are all important for the health of the expectant mother and her baby. Food safety is also very important. This information will help you make safe decisions when selecting and preparing food for yourself and/or your family.

Sometimes, what we eat can make us sick. Food contaminated by harmful bacteria can cause serious illness. One type of bacteria, Listeria monocytogenes (this is a Gram-positive bacterium, motile by means of flagella). Some studies suggest that 1-10% of humans may be intestinal carriers of L. monocytogenes.

It has been found in at least 37 mammalian species, both domestic and feral, as well as at least 17 species of birds and possibly some species of fish and shellfish. It can be isolated from soil, silage, and other environmental sources. L. monocytogenes is quite hardy and resists the deleterious effects of freezing, drying, and heat remarkably well for a bacterium that does not form spores. Most L. monocytogenes are pathogenic to some degree.

These bacteria can cause an illness called listeriosis, the name of the general group of disorders caused by L. monocytogenes. Nature of Disease: Listeriosis is clinically defined when the organism is isolated from blood, cerebrospinal fluid, or an otherwise normally sterile site (e.g. placenta, fetus).

The Centers for Disease Control and Prevention (CDC) estimates that 2,500 people become seriously ill with listeriosis each year in the United States. Of these, one in five dies from the disease. The 1987 incidence data prospectively collected by CDC suggests that there are at least 1600 cases of listeriosis with 415 deaths per year in the U.S. The vast majority of cases are sporadic, making epidemiological links to food very difficult.

Listeriosis can be particularly dangerous for pregnant women and their unborn babies. Foodborne illness caused by Listeria in pregnant women can result in premature delivery, miscarriage, fetal death, and severe illness or death of a newborn from the infection.

What is Listeria?

Listeria is a type of bacteria found everywhere in soil and ground water and on plants. Animals and people can carry Listeria in their bodies without becoming sick. Despite being so widespread, most infections in humans result from eating contaminated foods.

The manifestations of listeriosis include septicemia, meningitis (or meningoencephalitis), encephalitis, and intrauterine or cervical infections in pregnant women, which may result in spontaneous abortion (2nd/3rd trimester) or stillbirth.

The onset of the aforementioned disorders is usually preceded by influenza-like symptoms including persistent fever. It was reported that gastrointestinal symptoms such as nausea, vomiting, and diarrhea may proceed more serious forms of listeriosis or may be the only symptoms expressed.

Gastrointestinal symptoms were epidemiologically associated with use of antacids or cimetidine. The onset time to serious forms of listeriosis is unknown but may range from a few days to three weeks. The onset time to gastrointestinal symptoms is unknown but is probably greater than 12 hours.

The infective dose of L. monocytogenes is unknown but is believed to vary with the strain and susceptibility of the victim. From cases contracted through raw or supposedly pasteurized milk, it is safe to assume that in susceptible persons; fewer than 1,000 total organisms may cause disease. L. monocytogenes may invade the gastrointestinal epithelium. Once the bacterium enters the host’s monocytes, macrophages, or polymorphonuclear leukocytes, it is bloodborne (septicemic) and can grow.

Its presence intracellularly in phagocytic cells also permits access to the brain and probably transplacental migration to the fetus in pregnant women. The pathogenesis of L. monocytogenes centers on its ability to survive and multiply in phagocytic host cells.

Most people are not at increased risk for listeriosis. However, there are some people who are considered at risk because they are more susceptible to listeriosis.

The main target populations for listeriosis are: pregnant women and their unborn babies and newborns during perinatal and neonatal infections; other at-risk groups include older adults and people with weakened immune systems caused by corticosteroids, anticancer drugs, graft suppression therapy, AIDS; cancer patients there are in particularly treatments such as leukemia; people with – although less frequently reported – diabetic, cirrhotic, asthmatic, and ulcerative colitis patients, kidney disease; the elderly; normal people – although, some reports suggest that normal, healthy people are at risk, although antacids or cimetidine may predispose.

A listerosis outbreak in Switzerland involving cheese suggested that healthy uncompromised individuals could develop the disease, particularly if the foodstuff was heavily contaminated with the organism.

Most healthy persons probably show no symptoms. The “complications” are the usual clinical expressions of the disease.

When listeric meningitis occurs, the overall mortality may be as high as 70%; from septicemia 50%, from perinatal/neonatal infections greater than 80%.

In infections during pregnancy, the mother usually survives. Successful treatment with parenteral penicillin or ampicillin has been reported. Trimethoprim-sulfamethoxazole has been shown effective in patients allergic to penicillin.

By carefully following food safety precautions, persons at risk for listeriosis can substantially reduce their chances of becoming ill.

Why is listeriosis especially dangerous for me and my child?

Hormonal changes during pregnancy have an effect on the mother s immune system that lead to an increased susceptibility to listeriosis in the mother. According to the CDC, pregnant women are about 20 times more likely than other healthy adults to get listeriosis.

In fact, about one-third of listeriosis cases happen during pregnancy. Listeriosis can be transmitted to the fetus through the placenta even if the mother is not showing signs of illness. This can lead to premature delivery, miscarriage, stillbirth, or serious health problems for her newborn.

Is Listeria transmitted from the mother to the baby through breast milk?

While there is a theoretical possibility that Listeria monocytogenes could be transmitted via mother’s milk, this has never been proven.

How will I know if I have listeriosis?

Because the symptoms of listeriosis can take a few days or even weeks to appear and can be mild, you may not even know you have it. This is why it’s very important to take appropriate food safety precautions during pregnancy.

In pregnant women, listeriosis may cause flu-like symptoms with the sudden onset of fever, chills, muscle aches, and sometimes diarrhea or upset stomach. The severity of the symptoms may vary. If the infection spreads to the nervous system, the symptoms may include headache, stiff neck, confusion, loss of balance, or convulsions.

Consult your doctor or healthcare provider if you have these symptoms. A blood test can be performed to find out if your symptoms are caused by listeriosis.

What is the treatment for listeriosis?

During pregnancy, antibiotics are given to treat listeriosis in the mother. In most cases, the antibiotics also prevent infection of the fetus or newborn. Antibiotics are also given to babies who are born with listeriosis.

What steps can I take to prevent listeriosis?

Monocytogenes has been associated with such foods as raw milk, supposedly pasteurized fluid milk, cheeses (particularly soft-ripened varieties), ice cream, raw vegetables, fermented raw-meat sausages, raw and cooked poultry, raw meats (all types), and raw and smoked fish. Its ability to grow at temperatures as low as 3°C permits multiplication in refrigerated foods.

USDA’s Food Safety and Inspection Service (FSIS) and the U.S. Food and Drug Administration (FDA) provide the following advice for pregnant women and all at-risk consumers:

• Do not eat hot dogs, luncheon meats, or deli meats unless they are reheated until steaming hot.
• Do not eat soft cheeses such as feta, Brie, Camembert, blue-veined cheeses, and Mexican-style cheeses such as “queso blanco fresco.” Hard cheeses, semi-soft cheeses such as mozzarella, pasteurized processed cheese slices and spreads, cream cheese, and cottage cheese can be safely consumed.
• Do not eat refrigerated pâté or meat spreads. Canned or shelf-stable pâté and meat spreads can be eaten.
• Do not eat refrigerated smoked seafood unless it is an ingredient in a cooked dish such as a casserole. Examples of refrigerated smoked seafood include salmon, trout, whitefish, cod, tuna, and mackerel which are most often labeled as “nova-style,” “lox,” “kippered,” “smoked,” or “jerky.” This fish is found in the refrigerated section or sold at deli counters of grocery stores and delicatessens. Canned fish such as salmon and tuna or shelf-stable smoked seafood may be safely eaten.
• Do not drink raw (unpasteurized) milk or eat foods that contain unpasteurized milk.

What can all consumers do to prevent listeriosis and keep their food safe?

The methods for analysis of food are complex and time consuming. The present FDA method, revised in September, 1990, requires 24 and 48 hours of enrichment, followed by a variety of other tests. Total time to identification is from 5 to 7 days, but the announcement of specific nonradiolabled DNA probes should soon allow a simpler and faster confirmation of suspect isolates.

Recombinant DNA technology may even permit 2-3 day positive analysis in the future. Currently, FDA is collaborating in adapting its methodology to quantitative very low numbers of the organisms in foods.

Because Listeria can grow at refrigeration temperatures of 40 °F or below, FSIS and FDA advise all consumers to:

• Use all perishable items that are precooked or ready-to-eat as soon as possible.
• Clean their refrigerators regularly.
• Use a refrigerator thermometer to make sure that the refrigerator always stays at 40 °F or below.

What should I do if I’ve eaten a food that has been recalled because of Listeria contamination?

If you have eaten a contaminated product and do not have any symptoms, most experts believe you don t need any tests or treatment, even if you are pregnant. However, you should inform your physician or healthcare provider if you are pregnant and have eaten the contaminated product, and within 2 months experience flu-like symptoms.

It’s important to learn how to protect yourself and your unborn baby from foodborne illnesses. Getting in the habit of eating a safe and nutritious diet not only benefits your baby, but will also give you peace of mind.

New information on food safety is constantly emerging. Outbreaks include the California episode in 1985, which was due to Mexican-style cheese and led to numerous stillbirths. As a result of this episode, FDA has been monitoring domestic and imported cheeses and has taken numerous actions to remove these products from the market when L. monocytogenes is found.

There have been other clustered cases, such as in Philadelphia, PA, in 1987. Specific food linkages were only made epidemiologically in this cluster.

CDC has established an epidemiological link between consumption of raw hot dogs or undercooked chicken and approximately 20% of the sporadic cases under prospective study.

Recommendations and precautions are updated as scientists learn more about preventing foodborne illness. You need to be aware of and follow the most current information on food safety. Consult your healthcare provider if you have questions.