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The Trouble with Listeria: Redundancy Equals Pathogenic Success

There’s something about Listeria that makes it a food safety nightmare. The bacterium has caused thousands of infections over the last few years with an alarming case fatality rate of 21%, primarily in the elderly. It can survive a in a number of environments, including low temperatures, acidic conditions and even high salt. Then there’s the rather problematic production of biofilms, which can resist disinfection. All told, the pathogen has become one of the most important – and as a result studied – foodborne threats.

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Featured

  Listeria Outbreaks

Active and previous outbreak investigations...

 Everything you need to know about deadly listeria outbreaks

Listeria can totally survive in your fridge... It is not intimidated by the “coldest” setting, because it can survive at temperatures ranging from about 0 to 50 degrees Fahrenheit. Both your fridge and freezer are well within the bacterium’s optimal growth zone.

 What to Do About Listeria

What’s tricky about listeria is that unlike most food-borne pathogens, it can multiply in the refrigerator. Pasteurization and cooking will kill the listeria bacterium, but contamination often occurs later in processing. So you might bring home some ready-to-eat deli meats, hot dogs or soft cheeses that have a trace of listeria contamination on them, put them in the fridge and a week or so later, while they still look fresh, find yourself eating a listeria-packed meal. Not that you would know right away. The symptoms of listeriosis can take anywhere from a few days to a few weeks to show up.

Previously Featured

Six Dead in Listeria Outbreak Linked to Pasta

Listeria monocytogenes is a bacterium that is found naturally in soil, water and animals and can end up in food during the harvesting, processing, preparing and packaging process. It thrives in unsanitary conditions, and it cannot be killed by the cold conditions in a fridge or a freezer.

What is listeria? A microbiologist explains the bacterium behind recent deadly food poisoning outbreaks

How can such a tiny organism bypass extensive disinfection efforts and wreak such havoc? As a microbiologist who has been working with listeria and trying to solve these mysteries, I’d like to share some insider secrets about this unique little pathogen and its strategies of survival inside and outside our bodies.

Here Are 3 Types Of Food That Are Most Likely To Carry Listeria Bacteria

If you want to avoid Listeria bacteria — and believe us, you do — experts recommend knowing what products can be contaminated, checking labels, and cleaning places where food is stored.

What to Know About the Risk of Food Poisoning From Listeria

For these reasons, the C.D.C. recommends that people in high-risk groups avoid foods commonly contaminated with listeria, including unpasteurized soft cheeses, premade deli salads, and cold-cuts, meats and cheeses that were sliced at a deli but have not been reheated. (The bacteria can be killed by heating food to a high enough temperature.) Another way to minimize your risk is to put food in the refrigerator within two hours of preparing it, Dr. Kovac said. And always keep your fridge at or below 40 degrees. Many people keep theirs at slightly higher temperatures that can allow listeria to thrive, Dr. Donnelly explained. A few degrees cooler can make “a huge difference.”

Why Does It Seem Like There Are So Many Listeria Outbreaks?

Listeria is bacterium that grows in foods stored at refrigeration temperature—40 degrees Fahrenheit—such as chopped lettuce, deli meats, and, of course, cheese. It can cause meningitis, septicemia, abortion, and even death when ingested. In fact, up to 20 percent of people with listeriosis die. Listeriosis is the third most deadly food borne illness, causing some 260 deaths each year, the CDC estimates.

Why Listeria bacterium is so hard to fight

The harmful and potentially deadly bacterium Listeria is extremely good at adapting to changes. Now research uncovers exactly how cunning Listeria is and why it is so hard to fight. The discovery can help develop more efficient ways to combat the bacteria.

All You Need to Know About Listeria

Called an “opportunistic pathogen,” Listeria is noted to cause an estimated 2,600 cases per year of severe invasive illness. Perhaps not surprisingly then, “foodborne illness caused by Listeria monocytogenes has raised significant public health concern in the United States, Europe, and other areas of the world.” As one noted expert observed, summarizing the history of these bacteria and their significance for public health...

How we can prevent more Listeria deaths

There are a number of things that make Listeria monocytogenes unique and differentiate it from other foodborne pathogens. First, this bacterium can actually grow at refrigeration temperatures, so refrigerating foods cannot be used as a strategy to combat this organism.

Keep Listeria Out of Your Kitchen

Contaminated food can bring Listeria into the home. Unlike most bacteria, Listeria germs can grow and spread in the refrigerator. So if you unknowingly refrigerate Listeria-contaminated food, the germs not only multiply at the cool temperature, they could contaminate your refrigerator and spread to other foods there, increasing the likelihood that you and your family will become sick.

Killer Cantaloupe, Scary Sprouts: What To Do?

Avoid foreign produce. Wash and peel your fruit. Keep it refrigerated. None of these common tips would have guaranteed your safety from the deadliest food outbreak in a decade, the one involving cantaloupes from Colorado. Whether it's sprouts or spinach, turkey or hamburger; whether the government doubled, tripled or quadrupled inspections, the truth is that no food will ever be completely free of risk.

Lethal Listeria Outbreak: Why Is This Bug So Dangerous?

It's important to note that Listeria typically isn't dangerous for most people. Rather, the bacteria typically only cause symptoms in people with weakened immune systems — such as pregnant women and older adults — who already have a reduced ability to fight any kind of infection, said Dr. Amesh Adalja, a senior scholar at The Johns Hopkins Center for Health Security in Baltimore. But unlike many other types of foodborne illnesses, Listeria also has the ability to get into people's central nervous system, leading to particularly serious complications.

Listeria Outbreak: Why More Of Us Didn't Get Sick

"The bacteria come in and in many cases, they'll die in the stomach," says Schaffner. But when acid in the stomach is altered, studies find that people seem to be more susceptible. For instance, taking medicines to reduce acid reflux appears to increase the risk of stomach bugs.

Listeria’s Archnemesis

Because this pathogen is so adaptive and can survive in so many locations, it’s notorious for being introduced within butchered meat or other products in food processing plants and can persist for decades. It’s also good at growing in the cold — in refrigerators or in winter, under grass, where cattle will graze on it after the spring thaw. That often causes listeria outbreaks among cattle in the spring, which can affect farmers, the food supply, and processing plants.

The Most Common Cause of Listeria Is Behind the Deli Counter, Study Shows

After analyzing the data, they determined that the vast majority of reported listeriosis infections — over 90% — were connected to deli meats, followed by salads, the cheeses and the seafood, and then frozen vegetables.

This Is Why You Want To Avoid A Listeria Infection At All Costs When You're Pregnant

When you get pregnant, eating soft cheeses or deli meat suddenly becomes out of the question because of potential listeria infection concerns. But how does a listeria infection during pregnancy affect your baby, really? Well, the consequences can be dire.

Why is Listeria so Deadly Dangerous?

Listeria invades and grows best in the central nervous system among immune compromised persons, causing meningitis and/or encephalitis (brain infection). In pregnant women, the fetus can become infected, leading to spontaneous abortion, stillbirths, or sepsis (blood infection) in infancy.

Why You Should Avoid Soft Serve At All Costs

The deeper you delve into the problems with soft-serve ice cream, the more hesitant you will probably be to choose it as a dessert. There are some risks related to the cleanliness of the machines that produce soft serve as well as the temperature of the mix during shipping, storage, and mixing. The pathogens that can lurk on or in the machines — like listeria and E. coli — may cause food poisoning, or could even be deadly for people with certain health risks.

Resources

Listeria Blog

The Listeria blog supplements Marler Clark's Web site www.about-listeria.com, a site that provides information about Listeria monocytogenes, the symptoms and risks of infection, testing and detection of Listeriosis, and how to prevent the spread of the Listeria bacterium.

FoodSafety.gov

Listeria is unlike many other germs because it can grow even in the cold temperature of the refrigerator. Listeria is killed by cooking and pasteurization.