PNEUMONIA BACTERIUM LEAVES TINY LESIONS IN THE HEART
The long-observed
association between pneumonia and heart failure now has more physical evidence,
thanks to research in the School of Medicine at The University of Texas Health
Science Center at San Antonio.
The researchers found
proof that Streptococcus pneumoniae, the leading cause of
community-acquired pneumonia, actually physically damages the heart. The
bacterium leaves tiny lesions that researchers detected in mouse, rhesus
macaque and human autopsy tissue samples.
"If you have had
severe pneumonia, this finding suggests your heart might be permanently
scarred," said study senior author Carlos Orihuela, Ph.D., associate
professor of microbiology and immunology at the UT Health Science Center San
Antonio.
It's not yet known
whether the small lesions contribute to increased risk of death in humans or if
the scarring that occurs afterward is permanent, ultimately diminishing cardiac
function in individuals who have recovered from a severe infectious disease
episode. The team will study the long-term ramifications in non-human primates
at the Texas Biomedical Research Institute's Southwest National Primate
Research Center.
Streptococcus
pneumoniae in the blood
invaded the heart and formed lesions in the myocardium, the muscular middle
layer of the heart wall, the researchers showed. The team identified mechanisms
by which the bacterium is able to spread across endothelial cells in cardiac
blood vessels to travel to and infect the heart.
"Fortunately, we
have a candidate vaccine that can protect against this," Dr. Orihuela
said. The Health Science Center, St. Jude's Children's Research Hospital in
Memphis, Tenn., and the University of Oklahoma have claimed intellectual
property protection on the vaccine project. The candidate vaccine acts to stop
both the movement of the infection into the heart and the toxin that kills
heart muscle cells called cardiomyocytes. The vaccine protected immunized
animals against cardiac lesion formation, the study showed.
Study limitations
included the small sample size of human tissues analyzed, the researchers
noted. The American Heart Association and the National Institutes of Health
funded the project. The journal PLoS Pathogen published the
study online Sept. 18.
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