Magazine article Newsweek

Cardiac Contagion

Magazine article Newsweek

Cardiac Contagion

Article excerpt

Is a germ to blame for America's leading cause of death?

CHLAMYDIA PNEUMONIAE IS NOT what you'd expect. It's less famous than its sexually transmitted cousin Chlamydia trachomatis, but it's far more widespread and may be far more dangerous. We all encounter the bacterium sooner or later, most of us more than once. It spreads through coughs and sneezes, causing a flulike respiratory condition that sometimes progresses to pneumonia. But a growing number of experts suspect this is only the beginning of the mischief the microbe causes. Though the case is far from closed, several lines of evidence suggest that Chlamydia pneumoniae can make its way into the walls of various blood vessels and linger for years, fueling the inflammation that causes heart attacks and strokes. No one is saying that infection is the sole cause of atherosclerosis, or that diet and exercise don't matter. But mounting evidence suggests that the Western world's leading cause of death is to some degree contagious--and that common antibiotics might help bring it under control. This is the tale of how scientists made the connection.

The hug first came under suspicion in 1988, when doctors Pekka Saikku and Maija Leinonen of Helsinki Center Hospital published a pair of intriguing studies. The first showed that people with coronaryartery. disease were more likely than healthy control subjects tc) have antibodies to C. pneumomae circulating in their blood. The second study turned up unusually high antibody levels in the blood of heart-attack victims. Most experts dismissed the Finnish findings as a statistical oddity. But Dr. Thomas Grayston, an epidemiologist at the University of Washington, was intrigued enough to launch a study of his own. Grayston documented the same pattern in Seattle that Saikku had seen in Helsinki, and eight research teams from five countries have since confirmed it.

Searching for evidence: But does the association mean anything? The presence of antibodies tells you only that a person has encountered a pathogen and mounted an immune response. It doesn't reveal whether the bug is still present or, if so, how it's affecting the body. With those questions in mind, researchers set out in the early '90s to look for direct evidence of C. pneumoniae in clogged, brittle blood vessels. The first break came in 1993, when a South African researcher spotted what looked like tiny, pear-shaped bacterial cells in tissue cut from diseased arteries during autopsies. Grayston's team analyzed snippets of the same tissue and detected C. pneumoniae's proteins and genetic material in 20 out of 36 samples.

Other labs followed, and most of them managed to find bacterial fingerprints by one method or another. But few experts paid much attention until 1995, when a team led by Dr. James Summersgill of the University of Louisville recovered the bug itself, alive and kicking, from a patient's blood vessels. The patient, a 56-year-old man undergoing a heart transplant, hadn't suffered any recent respiratory illness. Yet when researchers placed tissue from his coronary arteries in a culture dish, they got colonies of C. pneumoniae. Today, says Grayston, no one familiar with the literature denies that the microbe is associated with vascular disease. Whatever their age, sex or nationality, people with sclerotic arteries tend to show signs of infection. And unlike the other microbes sometimes found in damaged vessels, this one never shows up in truly healthy tissue.

Yet, as the germ hunters readily admit, finding the bug at the crime scene doesn't prove it's a criminal. No one has shown conclusively that C. pneumoniae causes the damage that leads to heart attacks and strokes, but there are good reasons to suspect that it plays a role. Scientists have long known that atherosclerosis is an inflammatory disease. It affects vessels throughout the body, but those supporting the heart and brain are particularly vulnerable. The trouble starts when our immune systems mobilize to remove fat, cholesterol and other irritants from vessel walls (chart). …

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