Researchers studying endocarditis have found that, in test on mice, 90% infected with a ‘cardiac strain’ of the food borne bacteria listeria monocytogenes developed endocarditis.

Endocarditis is an inflammation of the inner layer of the heart, the endocardium. When the source of the inflammation is found to be in an organism, such as bacteria, it is categorized as infective endocarditis.

According to the FDA, listeria monocytogenes is most often found in “raw milk, supposedly pasteurized fluid milk, cheeses (particularly soft-ripened varieties), ice cream, raw vegetables, fermented raw-meat sausages, raw and cooked poultry, raw meats (all types), and raw and smoked fish.”

Listeria monocytogenes can cause mild food poisoning symptoms in healthy people, and death in more vulnerable patients.

But now researchers at the University of Illinois at Chicago College of Medicine have found that certain strains, possibly due to the proteins on the outside of the bacteria, can infect the heart.

“Usually with endocarditis there is bacterial growth on heart valves, but in this case the infection had invaded the cardiac muscle,” Nancy Freitag, who headed up the research, said in a release.

“As foods are being produced with a longer and longer shelf life, listeria infection may become more common. In combination with an aging population that is more susceptible to serious infection, it’s important that we learn all we can about these deadly infections,” she added.

With additional research, doctors may be able to identify the endocarditis causing strain of listeria monocytogenes by the proteins, which would be helpful in treating patients who may be more susceptible to infection, such as the elderly or those with immunodeficiency issues.

The study is published in the current issue of the Journal of Medical Microbiology.