The Food and Drug Administration (FDA) has started look for microbial contamination in a processed avocado, guacamole, and a variety of fresh herbs. The agency wanted to conduct tests on basil, cilantro, and parsley because they are often eaten without a so-called kill step like cooking, which would usually kill bacteria. The FDA also chose processed avocado because it has a lot of moisture and is not acidic, so bacteria can easily thrive in that environment. Their survey of these products has only just begun, and they have started to release some of their findings.
While the results for the fresh herbs from domestic sources are encouraging because none were found to harbor bacterial pathogens, so far, other results were not as good. The FDA determined that in 104 imported fresh herb samples, four were found to contain Salmonella. Although none tested positive for E. coli 0157:H7, three harbored a strain of E. coli that produces Shiga toxin.
The guacamole and avocado tests have also only begun recently, but some results were released. Again both domestic and imported samples were taken; one of the 49 imported samples carried Listeria monocytogenes, and three of 58 domestic samples assayed also harbored Listeria monocytogenes. Learn about the illness that Listeria causes from the video.
Outbreaks of foodborne illnesses that are connected to fresh herbs have already happened; there were nine from 1996 to 2015. Of those events, seven were due to the microbe Cyclospora cayetanensis, while E. coli O157:H7 and Shigella sonnei each caused one. The FDA wants to find out how much bacteria typically live in these environments, and they will begin looking for Cyclospora cayetanensis when it is known to cause illnesses - in the summer months.
The Centers for Disease Control and Prevention has reported that avocado or guacamole was linked to twelve outbreaks of foodborne illness over ten years. Nine of them were due to Salmonella, while E. coli caused three; 525 people got sick and 23 were hospitalized. None of them were started by Listeria monocytogenes, but the FDA found that bacterium after a recent test of avocado skin and fruit. They are investigating further.
The FDA has not yet said how much bacteria there was in each sample, so it may be that the levels were too low to cause illness. It is still a good idea to wash produce thoroughly before eating it and to make sure food is stored at the proper temperature. There is also no legal level of bacterial contamination in fresh produce.
University of Minnesota food safety expert Craig Hedberg told NPR that salmonella or listeria contamination is "an indication that companies need to pay more attention to sanitation in their plants." He added that while washing reduces bacteria levels in fresh herbs, it does not totally eliminate it.