Pneumonia Bacteria Can Compromise Heart Health

Streptococcus pneumoniae, the bacterium responsible for most cases of bacterial pneumonia, can invade the heart and cause the death of heart muscle cells.

Bacterial pneumonia in adults carries an elevated risk for adverse cardiac events, such as heart failure, arrhythmias, and heart attacks that contribute substantially to mortality, but how the heart is compromised has been indeterminate.

Scientists at the University of Texas Health Science Center (San Antonio, TX, USA) leading an international team, investigated the reasons for heart failure during invasive pneumococcal disease, when S. pneumoniae bacteria infect major organs such as the lungs, bloodstream, and brain, in mice, and subsequently confirmed some of their main findings in rhesus macaques and in heart tissue from deceased human patients.

The investigators used a variety of methods to obtain their results including histology; cardiac troponin assays determined using the mouse Cardiac Tn-I enzyme-linked immunosorbent assay (ELISA) kit (Life Diagnostics; West Chester, PA, USA); fluorescent microscopy of tissue sections and the images were acquired using the FV-1000 confocal system (Olympus; Center Valley, PA, USA); and cell based assays using flow cytometry on the BD FACSCanto II, (BD Biosciences; San Jose, CA, USA).

On the examination of the hearts of the mice, the team found microscopic sites of injury called microlesions in the heart muscle. S. pneumoniae were found within these microlesions, indicating the bacteria were able to invade and multiply within the heart. Looking in more detail, they identified dying heart muscle cells in the tissue surrounding microlesions. The tissues from three rhesus macaques that had died from pneumococcal pneumonia, the scientists found cardiac microlesions that were similar in size and appearance to those seen in mice, but without the presence of S. pneumoniae bacteria.

The authors concluded that ampicillin acts by breaking bacteria apart and releasing their contents, including pneumolysin and this could exacerbate the death of heart muscle cells. Alternative antibiotics that do not spill their bacterial targets' contents exist and might be advantageous. Having shown for the first time that S. pneumoniae can directly damage the heart, which could help explain the link between pneumonia and adverse heart events, the team also concluded that research is merited to determine the true frequency of cardiac microlesions in patients hospitalized with invasive pneumococcal disease, if modifications in antibiotic therapy improve long-term outcomes, and if prevention of cardiac damage is an indication for vaccination. The study was published on September 18, 2014, in the journal Public Library of Science Pathogens.

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University of Texas Health Science Center
Life Diagnostics
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