Listeria monocytogenes, a potentially deadly foodborne pathogen, has been found in lettuce samples, according to a story published at

WKMG-TV in Orlando reported Saturday that Listeria bacteria has been linked to lettuce imported from California and sold at a Fresh Market store. Store officials said late Friday the lettuce has been pulled and no reports of illness had been made.

"We will continue to monitor the situation to ensure our stores are taking all necessary precautions," Fresh Market said in a press statement.

Listeria monocytogenes (Listeria) is a pathogenic (disease-causing) bacterium that is food borne and causes an illness called listeriosis. It is frequently overlooked as a possible cause of illness due to its unique growth capabilities. First, it is somewhat difficult for laboratories to grow, and when they do so, Listeria can be confused with common harmless contaminants and disregarded. Second, most bacteria grow poorly when temperatures fall below 40°F, while Listeria survives in temperatures from below freezing (20°F) to body temperature and it grows best at 0°F to 50°F, including the temperature range that we use for refrigeration. As a result, Listeria may be transmitted in ready-to-eat foods that have been kept properly refrigerated. Its ability to grow in such diverse environments is just one of the many challenges presented by this dangerous bacterium.

It is estimated that Listeria causes approximately 1,600 cases of listeriosis annually, resulting in 415 deaths.

Listeriosis is the disease caused by Listeria monocytogenes. It is acquired by the ingestion of contaminated foods. Certain groups of individuals are at great risk for listeriosis. These are pregnant women (and their unborn children) and immunocompromised persons (e.g., transplant recipients). Among infants, listeriosis occurs when the infection is transmitted from the mother, either through the placenta or during the birthing process. These host factors, along with the amount of bacteria ingested and the virulence of the strain, determine the risk of disease.

Listeria can invade the body through a normal and intact gastrointestinal tract. Once in the body Listeria bacteria can travel through the blood stream, but are often found inside cells (they are "intracellular" pathogens). Listeria can co-opt the cell’s machinery to its own advantage by manipulating the host cell genes, and then move directly from cell-to-cell, avoiding many of the host’s defense mechanisms. The bacteria also produce toxins that damages cells.

For unknown reasons, in immune-deficient hosts Listeria invades and grows best in the central nervous system, causing meningitis and/or encephalitis (brain infection). In pregnant women, the fetus is most heavily infected, leading to spontaneous abortion, stillbirths, or sepsis in infancy.