Friday, April 27, 2018

Listeria in cheese

Microorganisms of the genus Listeria are widely distributed in nature, although with a limited number of species of medical and veterinary significance.

Listeria monocytogenes is an important human pathogen that can cause serious illnesses, with high mortality rates in susceptible individuals such as the elderly and people with immuno-compromised conditions.

It is a bacterium that is common in the environment and can be found in agricultural and food-processing settings, where it tends to persist once established. It might affect only the gastrointestinal tract, but may invade other parts of the body, potentially causing septicemia, meningitis, encephalitis, spontaneous abortion, and stillbirth.

Consumption of contaminated dairy products has been associated with cases and outbreaks of human listeriosis. Dairy products are good substrate for L. monocytogenes growth, as they contain proteins, lactose and trace elements. Outbreaks have been strongly associated with cheese consumption.

Fresh cheeses, which have been linked to human listeriosis outbreaks in the United States, are considered high-risk foods for L. monocytogenes contamination. Fresh cheeses are usually protected from contamination by refrigeration and usually packed with paper or shrink-wrapped with polyethylene or polypropylene with potential risk of proliferation of aerobic mesophilic bacteria, coliforms, molds or yeast.

Although L. monocytogenes is effectively inactivated by pasteurization, the prevention of post-processing contamination of milk products is of particular importance to dairy industries.
Listeria in cheese
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