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Listeriosis

What is listeriosis?

 

Listeriosis is a serious bacterial disease caused by the Gram-positive, rod-shaped bacterium, Listeria monocytogenes. The bacterium is widely distributed in nature and can be found in soil, water and contaminated food. Animals and food products such as vegetables can become contaminated from these sources. Infection with Listeria usually results in gastro-enteritis with symptoms ranging from mild to severe. However, in persons with weak immunity, listeriosis can lead to meningitis or septicaemia. In pregnant women, listeriosis may results in pregnancy loss (abortion) along with meningitis in their infant.

 

Who can get listeriosis?

 

Anyone can get listeriosis. However, those at high risk of severe disease are newborns, the elderly, immunocompromised individuals, pregnant women and their unborn babies and those with underlying conditions such as HIV, diabetes, cancer or chronic liver or kidney disease.

 

How is listeriosis transmitted?

 

Listeriosis is usually spread through the ingestion of contaminated food products, most frequently with raw or unpasteurised milk and soft cheeses, but also vegetables, processed foods, ready-to-eat meats and smoked fish products. Listeria can survive in normal temperatures associated with refrigeration (4°C). The Listeria bacterium can also be transmitted from a pregnant woman to her unborn baby during pregnancy or at the time of birth. Direct contact with the organism can cause skin lesions.

 

What are the signs and symptoms of listeriosis in humans?

 

The incubation period varies and can be between three and seventy days (median of three weeks). Up to 10% of people may be asymptomatic carriers. This figure may be higher in abattoir and laboratory workers who work with Listeria monocytogenes cultures. In the average healthy adult, infection is usually asymptomatic. Symptoms are usually mild and may include fever, myalgia, malaise and sometimes nausea or diarrhoea. In at-risk patients, spread of infection to the nervous system can cause meningitis, leading to headaches, confusion, stiff neck, loss of balance or convulsions. Bacteraemia may also occur. Pregnant women may present with a mild, flu-like illness associated with headache, fever and myalgia. However, infections during pregnancy can lead to premature births, infection of the newborn with permanent disability and miscarriage or stillbirth.

 

How is listeriosis diagnosed?

 

Diagnosis is made by culturing Listeria monocytogenes from clinical specimens such blood, cerebrospinal fluid (CSF), amniotic fluid, placenta or other sterile body fluids. A high index of suspicion is needed for diagnosis, as the organisms may be mistaken for skin contaminants (diphtheroids) on Gram stain.

 

How is listeriosis treated?

 

Gastro-enteritis due to Listeria usually does not require treatment. Meningitis or septicaemia due to Listeria can be life threatening and should be treated with intravenous antibiotics, such as ampicillin alone or in combination with other antibiotics such as gentamicin and trimethoprim-sulfamethoxazole. Listeria is resistant to cephalosporin antibiotics.

 

How can listeriosis be prevented?

 

Unlike most other foodborne pathogens, Listeria monocytogenes can grow in refrigerated foods that are contaminated. To prevent this, it is recommended to have fridge temperatures below 4 degrees Celsius; and freezer temperatures below 18 degrees Celsius. Therefore, those at high risk of listeriosis should avoid the following foods:

 

 

Click here for five keys to safer food.

 

There is no vaccine or pre-exposure prophylaxis for preventing infection. The main preventive measure is to always ensure that good basic hygiene is followed. This includes:

 

 

Source: http://www.health.gov.za/index.php/component/phocadownload/category/432