The dark side of bacteria

May 3, 2014 — Leave a comment

Bacteria are our friends…but not all the time.

While I believe that we need to keep the bacteria in our bodies happy and that the improved cleanliness of modern life may be causing problems, there is also no question that bacteria are our enemies as well. You don’t have to look very far to see examples of how bacteria can cause serious illness or even death – meningococal meningitis, pneumococcal pneumonia, salmonella and tuberculosis to name a few. In most cases, antibiotics are required to treat these infections (or vaccines to prevent the infections).

In recent years, bacteria have also been found to cause diseases that were not previously thought to be due to infections. One of the best examples is Helicobacter pylori, a bacterium that has been identified as the cause of stomach ulcers and gastritis (inflammation of the stomach) and a leading cause of stomach cancer. When the connection with bacteria was first suggested in the 1980s, most doctors thought this was a crazy idea but the scientists who discovered the connection, Barry Marshall and Robin Warren, went on to win the Nobel Prize in 2005 for this work.

Another surprising example is the possible connection between bacteria and heart disease. Bacteria are not thought to cause heart disease directly but they may play a role in getting the disease in people who eat meat. Bacteria in the stomach digest L-carnitine, a substance found in red meat, which produces another substance called trimethylamine-N-oxide (TMAO). Researchers at the Cleveland Clinic found that people with higher levels of TMAO in their blood were more likely to have heart disease and were at greater risk of developing heart disease and stroke. Another recent study suggests that patients with Crohn’s disease, a type of inflammatory bowel disease, have different bacteria in their guts than people who don’t have it, suggesting that bacteria may play a role in the development of the disease. Other research has suggested that bacteria may play a role in the development of rheumatoid arthritis, obesity, diabetes and other chronic medical problems. This may be because bacteria help our immune system function correctly. Scientists at Harvard Medical School have shown that a substance that is part of the outer coating of certain bacteria may be necessary to help in the body’s immune response.

So our relationship with bacteria is really complicated. Although certain bacteria like the meningococcus can cause life-threatening infections in many young, healthy people who are exposed to it, other bacteria like H. pylori, are less likely to cause disease. In fact, H. pylori has been present in humans for thousands of years. Some researchers think that with improvements in cleanliness, people get exposed to H. pylori at an older age than they used to and that the exposure later in life is what is leading to problems.

Bacteria are both our friends and our enemies. We need to figure out how we can get our bacteria to work harder at helping us, while making sure they don’t hurt us.

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