Listeria monocytogenes is already a virulent species of foodborne bacteria most often found in raw milk, soft-ripened cheeses and ready-to-eat cold cuts. It is particularly tenacious and can thrive even under refrigeration.

Now researchers say some strains of Listeria monocytogenes appear to have acquired an enhanced ability to invade and infect the heart.


Less common than Salmonella or toxic E. coli, Listeria can be far more deadly. While the majority of people infected suffer gastroenteritis and recover, Listeria kills about 16 percent of those infected, according to the Centers for Disease Control and Prevention. Other estimates place the fatality rate as high as 30 percent.

The bacteria typically affect the central nervous system or the fetus during pregnancy, but the new research indicates some unique but not uncommon strains of the pathogen target the heart, and that these variants may have adapted to increase their ability to invade heart cells.

According to a study led by Nancy Freitag, a professor at the University of Illinois Chicago, once these variant Listeria infect the heart, they can replicate faster than other strains.  Freitag and colleagues reported their findings in a paper published online Wednesday in the Journal of Medical Microbiology.

Freitag, in various interviews this week, said one implication of the study may be an increased risk of serious heart disease among those who become infected with Listeria.  During an outbreak of Listeria involving one of these strains, she said medical personnel should be aware that there’s a heightened potential for cardiac infection.

The study was supported by the U.S. Public Health Service and the American Heart Association.

  • Doc Mudd

    Listeriosis has long been recognized as one of the more damaging infectious diseases. It can make a real mess, literally punch holes in the central nervous system.
    It’s not something to be taken lightly. If you come down with a good case of listeriosis, you’ll sure know you got into sumpthin’. It will give you a whole new, realistic outlook on the relative pros and cons of ‘back to nature’ and ‘back to the good ol’ days’ of grubbing for a living. Hell, you’ll just be praying you can get ‘back to normal’ before L. monocytogenes is finished with you.

  • Thanks Doc Mudd! You may be interested in the following link to a program (free!) that my organization developed for the FDA. It focuses on Pregnant Hispanic women who happen to be at high risk for Listeriosis, but the info is worth a look for anyone interested.

  • Minkpuppy

    Listeria is one of my top 3 scary bugs, the other 2 being STEC E. coli’s and Brucella abortus.
    Brucellosis is no joke-I know a fellow inspector who discovered he was infected with it only after he nearly had a heart attack. He was running an extremely high fever when he got to the hospital and had the foresight to tell the doctors “Hey, I’m a meat inspector and I’ve been exposed to cattle with brucellosis” so they tested for it. The bacteria did serious damage to his cardiovascular system. I also know a veterinarian that has it–it flares up and causes problems years after the initial infection and treatment. I understand that it can be very painful.
    The public has become so disconnected from our livestock and food supply that they don’t understand the risks of these bacteria anymore.