Listeria Can Lead to Fatal Heart Infection

CHICAGONew research from the University of Illinois reveals Listeria monocytogenes has the potential to invade the heart and lead to serious and difficult to treat heart infections, according to a new study published in the Journal of Medical Microbiology. The findings suggest approximately 10 percent of serious Listeria infections involve a cardiac infection, with more than one-third proving fatal.

Researchers sought to determine whether patient predisposition led to heart infection or something different about the strain caused it to target the heart. They obtained an unusual strain of Listeria that had been isolated from a patient with endocarditis. Usually with endocarditis there is bacterial growth on heart valves; however, in this particular case the infection had invaded the cardiac muscle.

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. In the spleen and liver, organs that are commonly targeted by Listeria, the levels of bacteria were equal in both groups of mice. They also found 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. The researchers obtained more strains of Listeria, for a total of 10, and did the same experiment. They found that only one other strain also seemed to also target the heart.

They infected the heart of more animals and were always infecting heart muscle and always in greater number," they said. Some strains seem to have this enhanced ability to target the heart for infection. These strains seem to have a better ability to invade cardiac cells."

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.