Listeriosis monocytogenes is an infectious bacterium widely found in soil, water, and some animal species. These bacteria can cause severe illness, potentially leading to death in immunocompromised patients. Patients most commonly develop an infection as a result of eating contaminated food, including foods handled by people with an active Listeriosis monocytogenes infection. The disease caused by these bacteria is called listeriosis.
This species is Gram positive, and it is an example of a facultative anaerobe, a bacterium capable of surviving in oxygen-rich environments as well as those without air. This can make it difficult to combat, as it will readily thrive anywhere it can find nutrients, regardless of the surrounding environment, unlike other bacteria that can be eradicated with techniques like aerating foods to discourage the growth of anaerobic bacteria. Some organisms, including some humans, naturally carry colonies of Listeriosis monocytogenes in their digestive tracts without ill effects.
Soft, unaged cheeses are a common culprit for listeriosis infections, although the bacteria are also found in meats. Patients can develop fatigue, fever, and gastrointestinal distress, including nausea, diarrhea, and vomiting. A healthy patient may make a full recovery, but in patients with weak immune systems, Listeriosis monocytogenes can enter the bloodstream, causing sepsis. It is also capable of crossing the blood-brain barrier, leading to meningitis, a severe infection of the tissues that surround the brain and spinal cord.
AIDS patients, cancer patients, young children, and pregnant women are most at risk for serious complications from Listeriosis monocytogenes infections. Advisements to avoid soft cheeses during pregnancy, particularly in the third trimester, are the result of concerns about listeriosis. In these patients, the body may not be able to fight the infection, even with the assistance of antibiotic drugs to attack the bacteria. The patient may need hospitalization and supportive therapy to address issues like brain swelling or organ failure caused by the infection.
There are some options for reducing the risk of exposure to Listeriosis monocytogenes, including washing the hands well before handling food and eating, keeping food in properly chilled conditions, cooking food thoroughly, and avoiding water from untreated sources. For patients at particular risk, it is advisable to avoid foods linked with listeriosis infections altogether, to err on the side of caution. Infection with any food-borne illness can be very dangerous for patients who cannot fight microorganisms. Caregivers of immunocompromised patients need to be particularly careful about food handling to avoid exposing their charges to unnecessary risks.