Consumer Reports finds potentially deadly bacteria in pre-washed greens

A new report out Friday reveals some leafy greens recently sold at supermarkets were contaminated with a potentially deadly bacteria. Consumer Reports says it tested nearly 284 samples of fresh greens like lettuce, spinach and kale and found six of those samples tainted with listeria.

Consumer Reports says the six contaminated samples included both pre-washed and unbagged greens sold at retailers in Connecticut, New Jersey, and New York in June, including Acme, Costco, Hannaford, and Whole Foods. All of the retailers stress that food safety is a top priority, and public health officials have not reported any illnesses or concerns following their own inspections.

Consumer Reports notes their study is not large enough to draw any conclusions about a specific brand or retailer, but rather is a "snapshot" intended to highlight that more needs to be done to ensure safety.

In a statement to CBS News, a trade association that represents retailers, wholesalers, and suppliers that sell products to grocery stores said, "the incidents outlined in consumer reports … remind us that the entire supply chain has a responsibility for safe food handling."

One way to reduce the risk of listeria infection from greens like spinach and kale is to cook them. 

Some common symptoms of listeria infection

• Headache, stiff neck, confusion, loss of balance, and convulsions as well as fever and muscle aches
• Pregnant women may present symptoms differently. Typically they only experience fever and other flu-like symptoms, such as fatigue and muscle aches. The CDC warns, however, that infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.