Listeria is a food borne bacteria. It grows best in wet conditions. Poisoning with Listeria monocytogenes can cause muscle pain. The person can also feel sick to the stomach and even experience diarrhea – the uncontrolled expulsion of wastes from the body.
Listeria can be a serious health threat for pregnant women and older adults. It can also threaten people with weak immune systems, like those with HIV, the virus responsible for the disease AIDS.
The bacterium is everywhere in the environment, but usually grows in water. So, crops that are harvested shortly after they have been watered are likely to contain unsafe levels of disease-causing Listeria.
Martin Wiedmann teaches food safety at Cornell University in New York State. He and other researchers are urging farmers to wait 24 hours after a rainfall or watering fields before they harvest crops. By waiting, he says, a field has enough time to dry out.
“You're more likely to find Listeria for a very short time. After one day, it drops back more or less to the baseline normal level that we find (in the environment). So, we found this effect in water, but it's very short-lived. Within a day, you are back to normal."
The findings were reported in the journal Applied and Environmental Microbiology.
In crops like spinach, Listeria levels were 25 times greater when harvested immediately after the plants were watered.
Martin Wiedmann says the bacterium can also be found in sandwich meat, especially when the meat is not kept to minus-four or minus-five degrees Celsius. He says there are a number of other settings where unsafe levels of Listeria can hide.
"And so it's important to have the tools in place to control this organism everywhere from primary production, to food processing plants to retail, to helping consumers make smart decisions on what foods to eat and how to cook food."
Martin Wiedmann notes that Listeria poisoning is less common in developing countries. In such areas, he adds, foods generally are not left in iceboxes or refrigeration equipment, another source of bacterial overgrowth.
Words in This Story
irrigation – v. to supply with water by using man-made equipment, such as pipes or waterways
immune system – n. the body’s natural defenses against diseases and infections
bacterium - n. any one of a group of small living things that can cause disease