Earlier this year the US Food and Drug Administration (US FDA) updated its draft guidance for the industry to control Listeria monocytogenes in ready-to-eat foods1. This is part of the Food Safety Modernization Act (FSMA), cGMP and preventive control requirements that the industry must adhere to.


While this is still a draft and the comment period will not end until July 17, 2017 there is likely to be little change when it is finalized. This is mainly because recalls involving Listeria monocytogenes contamination, or potential contamination, continue at a steady pace.


In 2017 so far, some of the items recalled in the US include burritos, spinach, waffles, pancakes, toast, cashew butter, basil pesto, smoked fish, peas, soybeans, many types of cheese, vegetable blends, vegetable noodles, stuffed mushrooms, pimento spread, tree nuts, frozen vegetables and raw pet food. Ingredients such as raw meat, poultry, seafood, produce and milk are potential sources of Listeria monocytogenes. Human and animal feces are the primary vehicle of contaminating these ingredients. Since ready-to-eat products are highly unlikely to be heat treated before eating, if they are contaminated with Listeria monocytogenes, this becomes a potential cause of illness in people.

Outbreak investigations

Listeria monocytogenes outbreak investigation can start in many ways, but the most common way an investigation starts is as happened with a recent soft cheese investigation2. The US Centre for Diseases Control (US CDC) reports that eight people became ill, hospitalized and two died from a strain of Listeria monocytogenes during the period September 1, 2016 to March 13, 2017 as per reports from four states. After public health employees interviewed the ill people it was that determined the most likely source was one company and brand of cheese. To determine this the states followed a tried and tested process in which tests are carried out on containers of the suspected items from the homes of the people made ill, as well as closed containers. If the closed containers test positive for the Listeria monocytogenes, strain recalls follow. Additionally, the US FDA visits the operations in question. In this case, the facility was inspected over seven different days. Fourteen major issues were noted by the US FDA, as presented in their form 483. Among those issues were poor employee hygiene, black and/or green mold in the facility and equipment in disrepair. The company recalled all their products on the market, which were being sold throughout the US.

While the firm was performing environmental sampling for Listeria species, 27% of those samples were positive and 18.5% of the positives were on food contact surfaces. Investigation into and action related to the positive results was poor which indicates either fear of investigation and taken action, or a lack of knowledge as to how to investigate and identify what actions need to be taken.


While Listeriosis infections reported are not as numerous as those for other pathogens, there were 2,161 confirmed cases in Europe in 20143, and in the US it is estimated that 1,6004 people become ill each year. The rate of hospitalizations and death from this bacterial infection is higher than for other foodborne diseases, especially among pregnant women and their new-borns, the elderly (65 and older) and those with compromised immune systems. Death rates are estimated at 16%-20% of those that become ill. Hospitalizations are reported to be up to almost 90%5 on diagnosis of this type of infection.

Testing requirements and programs

The US FDA and other countries health agencies, such as Health Canada6, have recognized testing for Listeria species and/or Listeria monocytogenes in the manufacturing environment and if found, then testing follows for Listeria monocytogenes in the product. Testing for Listeria can be performed by traditional plating, or by rapid testing methods such as Polymerase Chain Reaction (PCR), ELISA and others7.

While Shiga toxin producing E. coli such as E. coli O157:H7 can be found in raw meat, poultry, other animal products and sprouts, testing requirements and programs have been in effect in many locations throughout the world. For example, for sprouts regulation EC 2073/2005 specifies that, based on five samples from the same batch, the limit is an absence in 25 grams of Shiga Toxin producing E. Coli (STEC) O157, O26, O111, O103, O145 and O104:H48.

Flour contaminations

Lately there have been issues in Canada and the US, relating to the presence of E. coli O121 and 026 9,10 in flours. This leads to illnesses in people who handle the contaminated flour, or the raw dough that is made from the contaminated flour. While the risk of illness in this case is lower than that for consuming a ready-to-eat item contaminated with Shiga toxin E. coli there is still a risk of illness associated with the flour and the raw dough made from contaminated flour.

Of course, flour is not the only novel item that this pathogen has been found in. There was a recent recall of soy nut butter contaminated with E. coli O157:H7 where 32 people, including 28 children, became ill. Many lawsuits are proceeding against the company that own the product name and formula as well as the manufacturer. These companies have filed for bankruptcy and the lawyer of the ill clients will now sue the retailers who sold the product11.

This highlights the necessity to at least test the production environment and product for generic E. coli and if it is present, then checks must also be made to identify whether (or not) a Shiga toxin form of E. coli is present. Test methods can either be traditional or rapid depending on the speed required for results. It also follows that retailers must pay attention to the source of all the products that they sell12, and devise a strategy of due diligence to assure that these manufacturers adhere to regulations. One such strategy is the requirement that all facilities selling products to a retailer provide a Global Food Safety Initiative (GFSI) audit report with corrective actions, as well as demonstrable compliance to the FSMA cGMP and preventive control requirements.

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Jim Cook
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t: +1 973-461-1493

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1  U.S. Food and Drug Administration
2  U.S. Food and Drug Administration
3  European Food Safety Authority
4  Centers for Disease Control and Prevention
5  About Listeria
6  Canadian Food Inspection Agency
7  U.S. Food and Drug Administration
8  EUR-Lex
9  Canadian Food Inspection Agency
10 U.S. Food and Drugs Administration
11 Food Safety News
12 U.S. Food and Drugs Administration