Food-borne bacteria causes difficult-to-treat heart infections

WASHINGTON - Scientists have found that particular strains of a food-borne bacteria are able to invade the heart, leading to serious and difficult-to-treat heart infections.

The bacteria Listeria monocytogenes is commonly found in soft cheeses and chilled ready-to-eat products, according to researchers at the University of Illinois at Chicago College of Medicine.

For healthy individuals, listeria infections are usually mild, but for susceptible individuals and the elderly, infection can result in serious illness, usually associated with the central nervous system, the placenta and the developing fetus.

About 10 percent of serious listeria infections involve a cardiac infection, according to Nancy Freitag, principle investigator on the study.

These infections are difficult to treat, with more than one-third proving fatal, but have not been widely studied and are poorly understood.

Freitag and her colleagues obtained a strain of listeria that had been isolated from a patient with endocarditis, or infection of the heart.

They found that when they infected mice with either the cardiac isolate or a lab strain, they found 10 times as much bacteria in the hearts of mice infected with the cardiac strain.

Further, the researchers found that while the lab-strain-infected group often had no heart infection at all, 90 percent of the mice infected with the cardiac strain had heart infections.

Freitag’s team used molecular genetics and cardiac cell cultures to explore what was different about these two strains.

The results suggest that these cardiac-associated strains display modified proteins on their surface that enable the bacteria to more easily enter cardiac cells, targeting the heart and leading to bacterial infection.

The study appeared online in the Journal of Medical Microbiology. (ANI)