Listeria: The Foodborne Bacteria That Kills
First I want to thank all of you for being patient. As some of you know, I injured both my hands in a fall several years ago and typing causes them to swell and the joints to bend in ways they are not meant to bend. Making the infographic for my last post was a bit too much for my hands and I was unable to type for a while. So, the posts I had planned didn’t get done. While I was resting my hands, though, I caught up with friends and on some reading and housekeeping.
I was shocked when I opened one email after another from the USDA with multiple reports of food being recalled for possible or probable listeria contamination. Years ago, there would be one recall here and there, but over the past year or two the numbers have just kept rising and that has bothered me. I wondered why we were seeing this sudden upward trend in our food supply.
First, what is Listeria?
Listeria monocytogenes is bacteria and when present in our body we may get sick from it, the illness is called listeriosis.
Why is it important?
It is the one pathogen that has the highest mortality rate.
Where is it found?
It is found in dirt, water and some animals (poultry and cows). Any plats that sit in infected dirt or are watered with infect water may also have the bacteria on it. Unlike most bacteria, it likes cool to cold moist environments.
In our homes and businesses
Unlike all other food pathogens that live and thrive in temps of 41°-135°F, Listeria will continue to multiply in a cold environment (and does not die in the freezer). So a refrigerator, cooler, and air conditioning units (including evaporative cooling units) are breeding grounds. FoodSafety.gov states that “It can also live in food processing plants and contaminate a variety of processed meats.” One article stated that in food processing plants the listeria bacteria “can hide in the tiniest of nooks and crannies ready to attach itself to cool, moist foods” and start multiplying.
What I remembered from my ServSafe Manager’s Certification course was that it was the one bacteria that can continue to grow in the refrigerator, as stated above. The foods most affected are raw meat, UNpasteurized dairy products – and foods made from them (typically soft cheeses – especially Mexican type cheeses), and ready-to-eat food such as deli meat, hot dogs, smoked salmon, pates, meat spreads, and sprouts.
The one fruit they list is cantaloupe. 2011 was a particularly bad year for cantaloupes. In less than 4 months 147 people were identified with listeriosis from cantaloupe. 143 were hospitalized and 33 died.
Why? I guess since it sits on the ground and listeria is present in soil, that isn’t too surprising. But then you think, why not zucchini or cucumbers? They sit on the ground. If you’re like me, you wash cucumbers and zucchini. I seldom eat cantaloupe, but from what I see, most people don’t scrub a cantaloupe like they do cucumbers and zucchini. The thought is you’re only eating the inside, so you don’t have to wash it. But as you slice that cantaloupe the bacteria is carried on the blade of the knife and goes into the cantaloupe. There it starts multiplying on the moist surface. I didn’t see any recorded incidence of listeria with other melons, but I did see other bacteria and foodborne illnesses associated with other melons.
Who is at Risk?
Healthy adults are the least likely to get very sick from listeria monocytogenes. This is the reason we don’t see it in the news more. At risk are pregnant women, young children – especially newborns, the elderly and those with immune deficiency of any kind. This includes those who have had a transplant of any type, those with cancer, HIV, AIDS, and even alcoholics and diabetics.
If the gut fights it off, your symptoms will be similar to other foodborne illnesses: diarrhea and a fever, possible vomiting. Many people don’t even experience that. But if it goes beyond the gut, then it’s called invasive listeria and can cause serious symptoms and even death.
While a pregnant woman might only have mild to moderate flu-like symptoms, listeria is so serious to her unborn baby that the baby might die. The CDC states: “infections during pregnancy can lead to miscarriage (20% of the time), stillbirth (3% of cases), premature delivery, or life-threatening infection of the newborn.” Foodsafety.org states that babies born after exposure may have life-long health issues. Newborns, those over 65 and those with weakened immune systems may get sepsis (infection in the blood), pneumonia or meningitis (infection in the brain). Other symptoms can include headache, stiff neck, confusion, loss of balance, and convulsions in addition to fever and muscle aches.
When Will the Symptoms appear?
Herein lies the problem. While listeria in the gut may show symptoms within a day, invasive listeria may not show any symptoms for weeks – even up to 70 or 90 days. Usually symptoms appear in 1 to 4 weeks after exposure. This makes finding the source harder for the CDC. Often I can’t remember what I ate yesterday, let alone a month or two ago. And who would have any lunchmeat leftover or the packaging anymore from a month or two ago for the CDC to test? But the CDC will still take cultures, identify the genome and catalog it for similar cases. They will also ask many questions trying to determine the source of the contamination.
The GOOD NEWS
Most people aren’t in the high-risk category and may fight it off fairly easily even though it is the deadliest once it person does present with invasive listeria.
The CDC has done much to identify the strains that have caused illnesses through a process called whole-genome testing. MANY are caught early – even at the plant before the product leaves. Others are identified later, by matching identified strains from prior years to current testing. This allows manufacturers to issue a recall much earlier than in times past. So while we see many more recalls, it doesn’t necessarily mean there are more products with problems, just that the tests are so much more sensitive and accurate than ever before. We also keep food on the shelves longer, so a product manufactured 3 months ago might still be in your freezer.
While we don’t know of the long-term health effects of irradiation, some packaged deli meat has been irradiated after packaging so any listeria that may have found its way into the product should be killed.
As these pictures indicate, the numbers for total illnesses are on the decline, even with the two major events – the cantaloupe and the Blue Bell Creameries issues discussed below (the Dole issue was in 2016).
Food Recalls are voluntary, unless the FDA determines there is a serious health risk that is not being addressed and step in with a mandatory recall. While manufacturers can and do test for listeria at their manufacturing plants, the testing may be sporadic. Additionally, they are not required to report it when they do find it. They are allowed to “self-correct” the problem. This would include measures such as a deep cleaning/sanitizing and checking that procedures for safe handling are being done properly and correcting any that aren’t.
Examples of epic failures to self-correct:
Dole knew of a problem in their Springfield, OH plant for a year before they were pressured to issue a “voluntary” recall and closing the plant the Canadian Health Department determined had a problem.* Blue Bell Creameries knew it had a problem for two years before closing their plant.* In both these cases people died and many more were hospitalized from the products made at these plants. How many more were sickened and didn’t report the illness?
In a future blog, I will be addressing what we can do to lessen the likelihood of getting a foodborne illness such as listeriosis. Special instructions will also be given for those who are at a higher risk of getting listeriosis.
Meanwhile, let me recap:
- Listeriosis is considered the most deadly foodborne illness WHEN a person becomes ill enough to seek medical treatment for it.
- MOST people will never get sick from listeria and if they do, it is most often mild and doesn’t require any treatment.
- It may take up to 70 DAYS before symptoms appear.
- The following people are at the highest risk of getting sick and/or dying from Listeria monocytogenes:
- Pregnant women, especially in the final trimester, and their unborn babies
- Newborns, due to their immature immune systems
- People over 65
- People with immune deficiencies such as those with AIDS, HIV positive, organ transplants. In fact those with AIDS are 300n times more likely to get listeriosis.
- Those with cancer, diabetes, kidney disease
- People who take glucocorticosteroid medications (such as cortisone, prednisone…)
- From my research, the incidence of listeria monocytogenes seems to be diminishing, not increasing. The ability to detect it – and the strains that have caused serious illnesses and death – have become simpler and more exact causing more cases to be caught early. From what I can tell, this is the reason we see the increase in recalls.
Taking measures to strengthen the immune system is vital to help your body fight off many illnesses and diseases. That topic is for another day, another post.
This post is intended to inform, not to scare anyone. Proper food handling and sanitation at home as well as in industry prevents most cases of foodborne illnesses. As noted, we will take up that topic in a future post.
* according to reports on the web
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