Chlamydia" in coronary plaque. Coloured Trans- mission Electron Micrograph (TEM) through atheroma in a coronary artery of the heart, showing pear- shaped structures (red) believed to be Chlamydia pneumoniae bacteria. They are in vacuole spaces of a foam cell (yellow). Foam cells are fat-filled cells found in atheroma plaque that coats arteries in the disease of atherosclerosis. C.pneumoniae may increase plaque formation and scarring of the diseased arteries as the immune system fights the bacteria. By contributing to atherosclerosis, C. pneumonia may be a cause of heart attack & stroke. If so, antibiotic drugs may prevent heart attacks."