New 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.

Abstract

Cardiac infections caused by the food-borne bacterium Listeria monocytogenes represent a significant but poorly studied facet of disease. It is not known as to whether L. monocytogenes cardiac infections stem solely from host susceptibility, or if bacterial isolates exist that exhibit a tropism for cardiac tissue. Here we examine the cardioinvasive capacity of a recent L. monocytogenes cardiac case strain (07PF0776) as well as nine additional outbreak and clinical isolates. Mice infected with the cardiac isolate 07PF0776 had ten-fold more bacteria recovered from heart tissue than those infected with L. monocytogenes strain 10403S, a well characterized clinical isolate originally obtained from a human skin lesion. Additional L. monocytogenes isolates exhibited varied capacities to colonize the hearts of mice, however those with the highest efficiency of mouse cardiac invasion also demonstrated the highest levels of bacterial invasion in cultured myoblast cells. Our findings strongly suggest that sub-populations of L. monocytogenes strains have acquired an enhanced ability to target and invade the myocardium.

Francis Alonzo, III, Linda D. Bobo, Daniel J. Skiest and Nancy E. Freitag. J Med Microbiol (2011), DOI: 10.1099/jmm.0.027185-0

Listeria monocytogenes (Listeria) is a foodborne disease-causing bacteria; the disease is called listeriosis. Listeria can invade the body through a normal and intact gastrointestinal tract. Once in the body, Listeria can travel through the blood stream but the bacteria are often found inside cells. Listeria also produces toxins that damage cells. Listeria invades and grows best in the central nervous system among immune compromised persons, causing meningitis and/or encephalitis (brain infection). In pregnant women, the fetus can become infected, leading to spontaneous abortion, stillbirths, or sepsis (blood infection) in infancy.

Approximately 2,500 cases of listeriosis are estimated to occur in the U.S. each year. About 200 in every 1000 cases result in death. Certain groups of individuals are at greater risk for listeriosis, including pregnant women (and their unborn children) and immunocompromised persons. Among infants, listeriosis occurs when the infection is transmitted from the mother, either through the placenta or during the birthing process. These host factors, along with the amount of bacteria ingested and the virulence of the strain, determine the risk of disease. Human cases of listeriosis are, for the most part, sporadic and treatable. Nonetheless, Listeria remains an important threat to public health, especially among those most susceptible to this disease.