Listeria monocytogenes, the bacterium that causes the serious infection known as listeriosis is a scary microorganism even for normally healthy individuals. But for the very young, the very old, those with a compromised immune system, and pregnant women, listeria infections can cause severe consequences. The Center for Disease Control and Prevention (CDC) estimates each year 1,600 people in the United States experience listeriosis. The CDC also estimates that each year about 260 Americans will die from this infection. This makes Listeria monocytogenes infection the third leading cause of death due to foodborne illness.
Symptoms of listeriosis can vary to some extent from person to person and the specific part of the body infected. In general, Listeria monocytogenesinfection causes the generic fever and diarrheal illness common to foodborne bugs. These infections often go unreported. Sometimes they are attributed to a stomach bug or the person manages symptoms until the infection runs its course without the need of medical attention. So many cases of listeria infection remain undiagnosed. More invasive listeriosis is often reported though, as the bacteria leaves the intestinal tract and enters other parts of the body which causes additional and more severe symptoms and complications.
Symptoms of invasive listeriosis often begin between 1 and 4 weeks after consuming a food that is contaminated with Listeria monocytogenes. However, the CDC reports that some people experience the first onset of symptoms as late as 70 days after exposure, while other develop symptoms as few as one day after exposure.
Pregnant women often experience milder symptoms such as only a fever. Sometimes they may experience additional flu-like symptoms such as muscle aches or fatigue. While they seem to get off the hook with fewer personal complications, listeriosis during pregnancy can have dire consequences for the fetus. This could lead to premature delivery, miscarriage, still birth, or even life-threatening infection of the newborn baby.
Depending on the severity and site of infection, people other than pregnant women often experience symptoms such as headache, stiff neck, confusion, loss of balance, and convulsions. They most likely will also experience fever and muscle aches.
The people most commonly infected with Listeria monocytogenes are those who fall highest in risk for invasive infection. This includes people who are pregnant, older than 65 years old, and people with compromised immune systems.
Pregnant women are 10 times more likely than others to become infected with listeriosis. More specifically, Hispanic women are 24 more times as likely as others to become infected with listeriosis. Listeria monocytogenesis particularly serious in pregnant women because the infection can pass to unborn babies and affect pregnancy causing preterm labor, miscarriage, or stillbirth. Listeriosis can cause serious illness and possibly death in newly born babies.
Pregnant women should protect themselves by avoiding foods that are common carriers for Listeria monocytogenes. This includes raw or unpasteurized milk or milk products such as cheese or yogurt. Other key foods to avoid include raw or lightly cooked sprouts (including but not limited to clover, alfalfa, mung bean, and radish sprouts). Hot dogs, lunch meats, cold cuts, or other deli meats, and fermented or dry sausages should be avoided unless heated to an internal temperature of 165 ⁰Fahrenheit. Take care to avoid juice from hot dog and lunch meat packages from contaminating other surfaces, utensils, or foods. Wash hands after handling these high-risk food products. Cut melons should either be consumed right away or refrigerated at 40⁰Fahrenheit (for no longer than 7 days). If the cut melon has been at room temperature for more than 4 hours, it should be thrown out. Pregnant women should avoid deli-counter refrigerated pâté or meat spreads and opt for those that are canned or shelf-stable instead. These products should be refrigerated after opening. Refrigerated smoked seafood should also be avoided unless it is in a cooked dished. There is also a listeria risk with raw Latin American style cheeses such as: queso fresco, queso blanco, queso blando, queso Cotija, queso panela, queso ranchero, and cuajada en terrón.
Pregnant women who experience fever or other symptoms of listeriosis within two months of eating a high-risk food should contact their health care provider and explain the potential causes so that they can be tested and treated for this serious infection. However, if you are concerned you should seek advice from your health care provider.
Those who are in the high-risk group are those most likely to suffer potential long-term complications or severity of the illness. Some of these groups of people include:
One in four Listeria monocytogenes infections occur in those who are over 65 years old. But why does age play such a large role in susceptibility of this infection?
This is a complex question, because many factors are involved. First, the aging immune system is not as quick to recognize and rid the body of these harmful bugs. This includes those bugs that are responsible for foodborne illness. Chronic conditions are fairly common in adults over 65, such as diabetes, cancer, and taking medications that can also weaken the immune system. The stomach acid changes throughout our lifetime. It begins to decrease in amount, allowing more germs to survive.
Those with a compromised immune system are also in the high-risk category for Listeria infection. People with alcoholism diabetes, cancer, liver disease, kidney disease, and the more
obvious HIV and AIDS. Those with cancer are 10 times more likely than others to become infected with listeriosis. Those on dialysis treatment are 50 times more likely to become infected with listeriosis.
Listeria diagnostic tests can vary depending on what types of technology are available to the testing laboratory. Typical diagnosis generally involves a bacterial culture grown from a human sample such as blood, spinal fluid, or placenta on a growth medium known to respond only to Listeria monocytogenes. Additional genetic analysis is preformed to determine the strain and possibly genetic sequence of the bug so that it can be compared to other cases and potentially linked to an outbreak.
Listeria monocytogenes is a bacterium. Bacterial infections such as listeriosis are treated with antibiotics. But treatment procedures vary and are dependent on the individual and outcomes of diagnostic tests, as well as risk factors. The antibiotic regimen can be as simple as oral ampicillin or amoxicillin. But if blood culture indicated blood contamination, intravenous (IV) ampicillin and gentamicin are often in the treatment plan. And if the infection is invasive and blood infection is indicated, IV ampicillin and gentamicin are often given to patients for between 14 and 21 days.
According to FoodSafety.gov, those who are in the high-risk group for Listeria infections should avoid eating:
Listeria is one of the new bacteria that thrive in cold environments. This makes it very hard to kill and keep out of a food processing environment, like an ice cream factory. There are some simple things though that can reduce the risk of infection: