Listeria – the facts.

A recent recall of Sabra hummus, Blue Bell Ice Cream, and Jeni's Ice Cream made the news!  And with many of us, including our children, by loving these foods, their  impact has been far-reaching.  Thousands of cases of Sabra Hummus were removed from grocery shelves due to suspected contamination with Listeria monocytogenes bacteria. All of Blue Bell and Jeni's products were removed from freezers, and Jeni's retail operations have closed until the source of contamination can be located, and decontaminated.

We’ve all heard of Salmonella, Staph food poisoning, and even campylobacter….but Listeria?

What is Listeria?

Listeria is one of the most dangerous of food-borne bacteria, and it’s especially risky to people with compromised immune systems – like pregnant women, the elderly and people with chronic disease resulting in weakened immunity.

It’s a bacteria that thrives in cold temperatures, and it can grow and multiply in the refrigerator. It can be found in uncooked meats and vegetables. It can be found often in food that is already cooked but poorly refrigerated, or frozen, but contaminated before-hand. It’s found in soil and ground water, and it’s commonly found in unpasteurized dairy products or cheeses that are contaminated after processing.

Listeria is killed by cooking and pasteurization, however foods already cooked or pasteurized can be reinfected as a result of poor food storage practices.

It’s estimated that half of Listeria cases are traced back to fruit (cantaloupe and other melons have been affected in the past), and another 30% from dairy products.

Who is at risk?

However, although common in the environment, Listeria rarely causes infections in people.  Exposure to the bacteria most of the time DOESN’T RESULT IN ILLNESS. But when it does (like the Jalisco cheese outbreak in the 1980’s, and most recently the cantaloupe outbreak in 2011), it dramatically causes death in up to 1 in 6 infected.

Here are some stats from, showing the relative risk of death of common food-born bacteria.  Listeria tops the list.

Listeria - 260 deaths, 1600 cases.  1/6 die.

Salmonella - 250 deaths, 1,200,000 cases. 1/4800 die.

Campylobacter - 76 deaths, 1,400,000 cases. 1/18,000 die.

Pregnant women constitute 14% of all cases and are 10x more likely than the general population to get Listeria infection.

Older adults comprise 58% of all cases with adults 65 years and older 4x more likely to be infected.

People with weakened immune systems, ie, those on chemotherapy or radiation, those who have liver or kidney disease, diabetes, alcoholism, and those with HIV/AIDS are also at high risk.

How do you contract it and what are the symptoms?

Eating food or liquids contaminated with Listeria is the route it takes into the body. For most people, there may be NO symptoms, or mild symptoms like diarrhea, vomiting,  abdominal pain, low grade fever or muscle aches. Mild symptoms usually resolved without any intervention and are self-limited.

However, in some, Listeria gains entry into the blood, and can travel to any organ, can cross the blood brain barrier into the liquid coverings of the brain, and can even travel across the placenta and infect a fetus. In pregnant women, premature labor and early delivery, miscarriage, and bloodstream infection, meningitis, and even death in the baby.

Hence, for those affected with moderate to severe symptoms, (prolonged fever, severe fluid losses from vomiting and diarrhea, severe abdominal pain, low blood pressure, profound  body aches and/or symptoms of bacterial meningitis), especially if in a high risk group, there is a need to be immediately hospitalized for treatment.

How is Listeria diagnosed?

The gold standards are 1) a history of ingestion 2) the presence of Listeria in a blood culture (ie proof that the bacteria is growing in the blood 3) the presence of Listeria in the cerebrospinal fluid (indicating it has spread to the nervous system, causing meningitis) 4) the presence of the germ in amniotic fluid, or 5) a high index of suspicion based on symptoms, even if Listeria is not found on diagnostic testing.

Testing stool for the presence of Listeria does not reveal an accurate diagnosis, nor do serologic tests (evidence of an immune reaction to the bug in the blood).

How is Listeriosis (the term for infection) treated?

It’s treated with intravenous antibiotics.  Depending on the site of infection (blood or nervous system) treatment lengths may vary.

Treatment is also supportive, as many requiring antibiotics may have dangerously low blood pressure, multiple organs involved, or require medications for seizures or strokes that complicate meningitis.

So how can we PREVENT Listeria infection? and other food-borne illnesses?

These are good rules for all, but IMPERATIVE if you are in a high-risk group (pregnent, over 65, immune compromized):

·      NEVER eat raw milk cheeses, unpasteurized dairy products, or soft cheeses, queso fresco, lunch meats or uncooked hot dogs

·      If eating sausages or hot dogs, NEVER eat them straight out of the refrigerator – heat until steaming hot and well cooked

·      Don’t eat refrigerated smoked seafood, unless contained in a cooked dish (ie smoked salmon, lox, etc)

·      Avoid unpasteurized (raw) juices

·      After washing your hands with soap and water for 20 seconds, wash hard vegetables and fruits under cold running water, scrub with a clean brush, then dry with a clean towel, and cut with a clean knife. DON’T BUY PRE-CUT melons at the market. Discard any melons left out more than 4 hours at room temperature.

·      For softer fruits and vegetables, wash with cold running water, dry with a clean towel.

·      Make sure your refrigerator is set to below 40 degrees (verify with a thermometer), and clean your refrigerator interior regularly with an ammonia or alcohol solution (both kill Listeria)

·      Put leftovers in shallow storage containers (the food gets colder, faster) and place immediately in your fridge.

·      Clean up spills in your refrigerator right away, especially juices from hot dogs, lunch meats, raw meat and raw poultry

·      Cook meat and poultry thoroughly

·      Use pre-cooked or ready to eat food as soon as you can and never consume after the “use by/eat by” dates

For a video link to Dr. JJ's Home and Family segment on this subject, go to :