Consumers should wash avocados before opening them to prevent listeria from the peel from contaminating the green pulp, according to U.S. authorities.

The Food and Drug Administration (FDA) launched a test of fresh avocados in 2014 as part of its new approach to test large numbers of samples from targeted foods over a short period to gather important data.

The agency collected 1,615 samples of avocados to test to determine the prevalence of Salmonella and Listeria monocytogenes in the commodity. About 70 percent of the avocados were imported and the rest were grown in the United States.

Three months after the testing began, the FDA began to test the avocado pulp, or the green, buttery portion that people love to eat.

The agency found that 0.24 percent of the pulp samples had listeria while 17.7 percent of the skin samples had listeria. The contaminated pulp was all from imported avocados while the contaminated skin samples were from both imported and domestic samples. Some skin samples also contained salmonella.

“The findings of this assignment affirm that Salmonella may be present on avocados and that Listeria monocytogenes may be present on or in the fruit,” the FDA stated.

The agency said that people should wash avocados, noting that the government’s food safety website advises that people “wash all produce thoroughly under running water before eating, cutting or cooking.”

The site also advises, “Even if you plan to cut the rind or peel off the produce before eating, it is still important to wash it first so dirt and bacteria aren’t transferred from the knife onto the fruit.”

Firm produce such as avocados should be scrubbed with a clean produce brush and dried with a clean cloth towel or paper towel to further reduce bacteria that may be present.

“Other practices associated with avocado consumption may reduce the risk to consumers as well. Consumers commonly slice avocados and extract the fruit’s pulp prior to eating it, discarding the fruit’s peel as they would a banana peel or an orange rind,” the FDA stated.

“Consumers also typically eat avocados shortly after slicing the fruit as its pulp tends to brown quickly once exposed to oxygen. These practices generally limit the amount of the pathogen, if present, that consumers may be exposed to.”

Salmonella and Listeria

According to the Centers for Disease Control and Prevention, the listeria bacteria causes listeriosis, a serious infection.

“An estimated 1,600 people get listeriosis each year, and about 260 die. The infection is most likely to sicken pregnant women and their newborns, adults aged 65 or older, and people with weakened immune systems,” the agency stated.

The agency noted that salmonella causes about 1.2 million illnesses in the United States every year, sending approximately 23,000 people to the hospital and killed some 450 people.

Salmonella is primarily caused by contaminated food, with food being the source of about 1 million of the illnesses.

“Most persons infected with Salmonella develop diarrhea, fever, and abdominal cramps 12 to 72 hours after infection. The illness usually lasts 4 to 7 days, and most persons recover without treatment,” the agency stated. “However, in some persons, the diarrhea may be so severe that the patient needs to be hospitalized.”