How clean are those pre-washed salad greens?

A new study by Consumer Reports finds traces of bacteria in bagged salad — even those labeled "pre-washed."

The lab tests of 208 containers of 16 brands of greens found several types of bacteria, including coliforms and Enterococcus, a type of organism found in the human digestive tract and the environment, which could be a signal of inadequate sanitation, the report states.

These bacteria don't generally make healthy people sick (nor did the tests find E. coli or salmonella, pathogens that can be deadly). Still, the report calls them "indicator" bacteria, a sign that "not enough is being done to assure the safety or cleanliness of leafy greens," said Michael Hansen, a senior scientists at Consumer Union, the nonprofit that publishes Consumer Reports, in a statement.

Consumer Union also issued a report urging the FDA to set safety standards for greens.

Your best bet to avoid any problems, rinse those greens, even the ones whose packages claim they have already been washed.