Listeriosis is a serious foodborne illness caused by the bacterium Listeria monocytogenes. This organism is widespread in the environment, found in soil, water, and even animal feces, and can contaminate various foods. Listeria monocytogenes can grow at refrigeration temperatures, making it a particular concern for food safety. Understanding the signs of a potential infection is important for timely action.
Identifying Symptoms
Symptoms of listeriosis can vary, ranging from mild, flu-like signs to more severe manifestations, depending on whether the bacteria have spread beyond the digestive system. Mild symptoms often include fever, muscle aches, nausea, vomiting, and diarrhea, appearing within 24 hours and lasting one to three days. When the infection spreads to other parts of the body, known as invasive listeriosis, symptoms become more severe. These can include headache, stiff neck, confusion, loss of balance, and even convulsions. Invasive listeriosis symptoms typically appear within two weeks of exposure, but can emerge up to 90 days later.
Certain groups face a heightened risk of serious illness from listeriosis. Pregnant women, newborns, adults over 65, and individuals with weakened immune systems are vulnerable. Pregnant women may experience only mild or no symptoms, yet the infection can lead to serious complications such as miscarriage, stillbirth, premature delivery, or life-threatening infection in the newborn. Individuals with compromised immune systems, due to conditions like cancer, HIV/AIDS, diabetes, or certain medical treatments, are more susceptible to severe listeriosis.
Medical Evaluation and Diagnosis
Seek medical attention if listeriosis is suspected, especially for high-risk individuals or those with severe symptoms. Consult a healthcare provider if fever, muscle aches, upset stomach, or loose stools develop, particularly after consuming potentially contaminated food. Inform the doctor about any recent consumption of possibly contaminated food.
Diagnosis involves laboratory tests to detect the Listeria bacteria. Healthcare providers may collect samples of blood or cerebrospinal fluid (CSF) for culture. A CSF culture is performed if the infection is suspected to have spread to the brain and spinal cord, as Listeria can cause meningitis. Stool tests are not considered reliable for diagnosing invasive listeriosis.
Treatment and Recovery
Once diagnosed, listeriosis is treated with antibiotics. Ampicillin, sometimes combined with gentamicin, is often the preferred antibiotic. The duration of antibiotic treatment can vary, depending on the severity of the illness and the patient’s immune status. For individuals with mild symptoms and no heightened risk, treatment might not be necessary.
Early diagnosis and treatment with antibiotics can improve outcomes, particularly for pregnant women, potentially preventing the infection from affecting the baby. In more severe cases, or for individuals in high-risk groups, hospitalization may be necessary to administer intravenous antibiotics and provide supportive care. Recovery involves completing the full course of prescribed medication, even if symptoms improve, to ensure the infection is fully cleared.
Preventing Future Infections
Preventing Listeria infections involves careful food handling and awareness of high-risk foods. Practicing good hygiene, such as washing hands with soap and warm water for at least 20 seconds before and after handling food, helps minimize contamination. Washing raw fruits and vegetables thoroughly under running water before consumption is also important.
Avoiding cross-contamination is another important step. This includes keeping uncooked meats separate from ready-to-eat foods and using different cutting boards and utensils or thoroughly cleaning them between uses. Cooking all foods of animal origin, such as meats, to their appropriate internal temperatures helps eliminate bacteria. For high-risk individuals, certain foods are best avoided or consumed only after proper reheating, such as:
- Unpasteurized dairy products
- Soft cheeses
- Deli meats
- Hot dogs
- Pâté
- Raw sprouts
- Pre-cut fruits and vegetables
Deli meats and hot dogs should be reheated until steaming hot.
Maintaining proper refrigeration temperatures, specifically 41°F (5°C) or below, can slow the growth of Listeria. Regularly cleaning refrigerators and food preparation surfaces, especially after handling raw items or suspected contaminated foods, is also advised. If there is any doubt about the safety of a food item, discarding it is the safest course of action.