Keeping Food Pathogens at Bay in Fresh Fruits and Vegetables Our expertise

Listeria monocytogenes (L. monocytogenes) is a species of pathogenic (disease-causing) bacteria that can be found in moist environments, soil, water, decaying vegetation, and animals. It can survive and even grow under refrigeration and other food preservation measures.

Listeria can also be difficult to fully remove from food processing facilities. If a facility has Listeria germs, the germs can spread to food that touches contaminated equipment or surfaces. Listeria can also spread from contaminated food to surfaces. It can even grow on foods kept in the refrigerator. The good news is that Listeria is easily killed by heating food to a high enough temperature.

People can get infected by eating the following:

• Raw vegetables that have been contaminated from the soil or contaminated manure used as fertilizer
• Sprouts need warm and humid conditions to grow. These conditions are also ideal for the growth of Listeria and other harmful germs. Germs can grow on the inside and outside of sprouts, so washing them does not remove all germs. Homegrown sprouts can also have germs because they need the same conditions to grow
• Melons are more likely than many other fruits to be contaminated with Listeria. This is because they have low acidity and can be kept in the refrigerator for a long time. Both these conditions support the growth of Listeria
• Soft cheeses are more likely than hard cheeses to be contaminated with Listeria because of their high moisture, low salt content, and low acidity. These conditions support the growth of Listeria. Soft cheeses made with unpasteurized milk or made in facilities with unclean conditions are even more likely to be contaminated. Although pasteurizing milk kills germs, cheese made with pasteurized milk can still get contaminated during cheese-making
• Certain processed foods such as hot dogs, cold cuts, deli meats, and fermented or dry sausages can be contaminated with Listeria when they are made or prepared at facilities where Listeria persists. Although cooking, fermenting, or drying kills germs, these meats can get contaminated afterward if they touch surfaces with Listeria. Refrigeration does not kill Listeria but reheating before eating will kill any germs that may be on these meats
• Raw (unpasteurized) milk and raw milk products. Pasteurization heats milk to a high enough temperature for a long enough time to kill germs that can make you sick. Raw milk and products made from it, including ice cream and yogurt, can contain Listeria and other harmful germs. These germs can get into raw milk in multiple ways, including unclean conditions at the dairy farm and contact with animal poop. It is recommended that everyone choose pasteurized milk and dairy products

Fresh Ideation Food Group in the USA recalled products in January 2023 due to possible Listeria contamination. The recall was initiated after company samples tested positive for the bacteria. No illnesses have been reported to date. The recalled products were sold in retail locations, vending machines, and during travel with transportation providers. The products include sandwiches, salads, snacks, yogurt, wraps, and related products.

A second recall for possible Listeria contamination was announced by the USDA’s Food Safety and Inspection Service (FSIS) on January 29, 2023. The recall was for 52,914 pounds of sausage commonly used to make charcuterie boards. On February 3, 2023, the total pounds of recalled sausage increased to 69,255. The FSIS discovered Listeria monocytogenes on surfaces which the product came in contact with during a routine inspection. To date, there have been no confirmed illnesses reported.

1. Keep the kitchen clean. Clean your refrigerator regularly with hot water and liquid soap. Prepare meats and vegetables separately and be sure to sanitize food preparation areas.

2. Keep the fridge cool. Because listeria can easily grow in cool temperatures, keep your refrigerator at 5 degrees Celsius or lower. The freezer should be at minus 18 degrees Celsius or lower.

3. It is recommended to choose pasteurized milk and dairy products. Pasteurization heats milk to a high enough temperature for a long enough time to kill germs that can make you sick.

4. Avoid eating soft cheeses such as queso fresco, queso blanco, panela (queso panela), brie, Camembert, blue-veined, or feta, unless it is labeled as made with pasteurized milk.

5. Always thoroughly heat sprouts first, even homegrown versions can harbor bacteria. When eating out, be sure to ask that no raw spouts be added to your food.

6. Always thoroughly wash any greens to be safe:

• Wash up for 20 seconds with soapy water both before and after handling any leafy greens
• Do not soak greens in the sink; that just spreads any bacteria on one leaf to all the leaves
• Remove any torn, bruised, or outer leaves
• Under running water, scrub each leaf gently and then dry the leaves with a clean cloth

7. Eat cut melon right away and throw away any unrefrigerated for four or more hours. Refrigerate cut melons at 5 degrees Celsius or colder for no more than seven days.

8. Avoid eating cold cuts such as bologna, hot dogs, lunch meats, fermented, or dry sausages or any other deli meats unless they are heated to steaming hot 74 degrees Celsius just before serving. 

9. When eating these foods at home should be careful not to allow juice from hot dogs and lunch meat packages to get on other foods or food preparation surfaces, plates, and utensils. Always carefully wash your hands after touching any type of hot dog, lunch, or deli meat.

10. Be aware of how long you store such foods in your home. Factory-sealed unopened packages of hot dogs, lunch, and deli meats should be thrown away after two weeks in the fridge.

Listeria is especially harmful to people including older adults (65 and older) people with weakened immune systems, health problems or take medicines that lower the body’s ability to fight germs and sickness, pregnant women, and newborns.

The signs and symptoms of Listeria infection vary depending on the person infected and the part of the body affected. One is an invasive illness, which means bacteria have spread beyond the intestines (gut). Invasive listeriosis happens when Listeria has spread beyond the intestines.

Symptoms of an invasive illness usually start within two weeks after eating food contaminated with Listeria.

Listeria can also cause an intestinal illness. This kind of illness is rarely diagnosed because laboratories do not regularly test patient stool samples for Listeria.

Symptoms of an intestinal illness usually start within 24 hours after eating food contaminated with Listeria and usually last one to three days.