Germ Theory

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02/26/1999

Feb. 26, 1999

Germ Theory

When you think of conditions like heart disease, most people generally think of causes like poor diet, lack of exercise, or environmental factors such as cigarette smoking. A new study out this week, however, suggests that perhaps bacterial infections may play a significant role as well. Researchers at the University of Toronto, the Ontario Cancer Institute, the University of Innsbruk and U.C. Irvine have discovered a mechanism that explains a link that had been commented on before, but never explained - why infection with Chlamydia pneumoniae (not the variety responsible for the sexually transmitted disease) often increases the risk of developing heart disease. Their report is published in this week's edition of the journal Science. The team of researchers found that a protein on the surface of three different forms of the Chlamydia bacterium was quite similar to myosin, a protein found in heart muscle. When the immune system kicks into action to try to fight off a Chlamydia infection, they say, immune cells sometimes inadvertently target the heart protein as well, causing inflammatory heart disease. The scientists managed to create heart disease in some mice by injecting them with Chlamydia. Not all the mice developed heart disease - the researchers believe that the differences are due to genetic factors that make some mice more susceptible than others Other diseases may have unexpected bacterial and viral connections as well. In recent years, scientists have discovered that a bacterium called H. pylori can cause stomach ulcers. Researchers are also looking at infections as playing a role in cervical cancer and liver cancer. Should heart disease be reclassified as an infectious disease? Could cancer be catching? We'll talk about it on this hour of Science Friday.

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