Sidd
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"Sustainable dairy business."
Posted on 22. Dec 2023
Listeria monocytogenes is the bacterium that causes the infection listeriosis. It is a facultative anaerobic bacterium, capable of surviving in the presence of oxygen.It can grow and reproduce inside the host’s cells and is one of the most virulent food-borne pathogens, with 20 to 30 percent of clinical infections resulting in death (van-de-Venter, 2000).Epidemiology
Listeria species are widely distributed in the environment and can be isolated from soil, plants, decaying vegetation and silage (pH 5.5) in which the bacteria can multiply. Asymptomatic faecal carrier occurs in man and animal species (Ibid).Pathogenesis
Listeria originally evolved to invade membranes of the intestines, as an intracellular infection, and developed a chemical mechanism to do so. This involves a bacterial protein “internalin” which attaches to a protein on the intestinal cell membrane “cadherin”.L. monocytogenes has also D-Galactose residues on its surface that can attach to D-Galactose receptors on the host cell walls. These host cells are generally M cells and Payer’s patches of the intestinal mucosa.Once attached to these cells, L. monocytogenes can translocate past the intestinal membrane and into the body. L. monocytogenes may invade the gastrointestinal epithelium. Once the bacterium enters the host’s monocytes, macrophages, or polymorphonuclear leukocytes, it becomes blood-borne (septicaemic) and can grow.Its presence intracellularly in phagocytic cells also permits access to the brain and probably trans-placental migration to the foetus in pregnant women (CDC, 2011).Symptoms
The symptoms of listeriosis usually last 7-10 days, with the most common symptoms being fever, muscle aches, and vomiting. Diarrhoea is another, but less common symptom. If the infection spreads to the nervous system it can cause meningitis, an infection of the covering of the brain and spinal cord (Bean & Griffins, 1990; Adams & Moss, 2008).Detection of toxin
Enrichment procedures are required for this organism. This involves inoculation of selective or non-selective broths that are incubated at 4°C for up to 8 weeks.An ELISA, using monoclonal antibodies, has been developed to identify listeria in food, and also DNA probe for detection of bacterium in dairy products (Niehaus, et al., 2011).Control and 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 (CDC, 2011).Preventing listeriosis as a food illness requires effective sanitation of food contact surfaces. Alcohol and Quaternary ammonium are an effective topical sanitizer against Listeria.Refrigerated foods in the home should be kept below 4°C (39.2°F) to discourage bacterial growth. Preventing listeriosis also can be done by carrying out an effective sanitation of food contact surfaces.Occurrence is worldwide. Most cases have been reported from Europe, North America and the Pacific islands.References
- Adams, M., & Moss, M. (2008). Food Microbiology. London, UK: RSC Press.
- Bean, N., & Griffins, P. (1990). Foodborne Diseases Outbreaks in the United States, 1973-1987: Pathogens, Vehicles and Trends. Journal of Food Microbiology, 53, 804-817.
- CDC. (2011). Estimates of Foodborne Illnesses in the United States. New York: Centers of Disease Control.
- Niehaus, A., Apalata, T., Coovadia, Y., Smith, A., & Moodley, P. (2011). An Outbreak of Foodborne Salmonellosis in Rural KwaZulu-Natal, South Africa. Foodborne Pathogens and Disease, 8, 693-7.
- van-de-Venter, T. (2000). Emerging food-borne diseases: A Global Responsibility. Durban: Department of Health, Republic of South Africa.
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