LISTERIOSIS
How many of us are aware of these small bacteria which causes serious food poisoning in humans? LISTERIA.
It is small Gram-positive rod shaped bacteria. There are two types, L. monocytogenes and L. ivanovii, widely distributed in Nature. We can isolate Listeria from raw meat, dairy products, vegetables, fruit and seafoods like fish, oysters, from ticks, flies, soil, water and animal feces. It is the 3rd most common bacterial cause of food poisoning.
Mode of spread:
Listeria is ubiquitous in the environment. It is primarily transmitted via the oral route after ingestion of contaminated food products, after which the organism penetrates the intestinal tract to cause systemic infections
L.monocytogenes causes the disease listeriosis, a serious infection caused by eating food contaminated with the bacteria. Listeriosis has been recognized as an important public health problem worldwide. It also causes listeriosis in animals and humans. L. ivanovii causes the disease in animals only, mainly sheep. The disease affects primarily pregnant women, newborns, and adults with weakened immune systems. The disease has mortality rate of > 25 %. The two main clinical manifestations are sepsis and meningitis. Humans are infected by consuming vegetables that have been contaminated from the soil or from contaminated manure used as fertilizer, by consuming infected animal meat, unpasteurized milk or foods made with unpasteurized milk. Certain processed foods — such as soft cheeses, hot dogs and deli meats that have been contaminated after processing
Pathology:
Listeriosis primarily causes infections of the central nervous system (meningitis, meningoencephalitis, brain abscess, cerebritis) and bacteremia in those who are immunocompromised. Encephalitis is the most common form of the disease in ruminant animals. In young animals, visceral or septicemic infections often occur. Intra-uterine infection of the fetus via the placenta frequently results in abortion in sheep and cattle. A person with listeriosis usually has fever and muscle aches, often preceded by diarrhea or other gastrointestinal symptoms.
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.
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
Pregnant women and their babies
Pregnant women are significantly more susceptible to listeria infections than are other healthy adults. Unborn babies can contract a listeria infection from the mother via the placenta. Although a listeria infection may cause only a mild illness in the mother, consequences for the baby may include: miscarriage, stillbirth, premature birth and a potentially fatal infection after birth. As in adults, the signs and symptoms of a listeria infection in a newborn can be subtle, but may include, little interest in feeding, irritability, fever and vomiting.
Lab Diagnosis: We can isolate the bacteria from blood and cerebrospinal fluid by culture methods. There are no reliable serological or stool tests. Ampicillin generally is considered antibiotic of choice; gentamicin is added frequently for its synergistic effects. Overall mortality rate is 20–30%.
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 foods such as soft cheeses. Listeria bacteria can survive refrigeration and even freezing. Hence I advise people at risk of infection should avoid eating the types of food most likely to contain listeria bacteria.
Food safety guidelines to prevent listeria infection:
First, wash your hands thoroughly with warm, soapy water before and after handling or preparing food.
After cooking, use hot, soapy water to wash the utensils, cutting board and other food preparation surfaces.
Always clean raw vegetables with a scrub brush or vegetable brush under plenty of running water.
Cook your food thoroughly to make sure your meat, poultry and egg dishes are cooked to a safe temperature
Don't eat soft cheeses such as feta, Brie, Camembert, blue cheese or Mexican-style cheeses unless it is pasteurized
Avoid consuming unpasteurized milk/ raw milk.
Avoid hot dogs, luncheon meats and deli meats, unless they're reheated until steaming hot.
Don't eat refrigerated pates or meat spreads.
Thus by following these simple steps we can protect ourselves and our family from Listeriosis food poisoning.
Author: Dr.Mohamudha Parveen Rahamathulla
Assistant Professor- Medical Microbiology
Department of Medical Lab Sciences
