Everyone can understand that bacteria can cause a disease through infection. Bacterial infections can cause huge inflammatory responses known as sepsis or result in a cut getting infected. But a bacterial infection causing ulcers? That seems weird.
This is a crazy story, but resulted in the 2005 Nobel Prize in Physiology and Medicine. In the 1980s, Dr. Barry Marshall found that the bacteria H. Pylori is often found in people with peptic ulcers. At this point, scientists didn't even think that bacteria could survive in the acidic environment of the stomach, much less cause a disease. Ulcers were obviously caused by stress or spicy foods or too much acid. Dr. Marshall was convinced of his hypothesis and went to test his theory in pigs, but for some reason he wasn't able to get the H. Pylori bacteria to infect the pigs. So one night, he drank an entire petri dish of cultured H. Pylori. As a side note - it is NOT a good idea to do experiments on yourself because you have no idea what will happen (movies have confirmed this over and over). However, three days later, he felt nauseous, after a week he started vomiting and an endoscopy found massive inflammation indicative of gastritis, and two weeks later he started taking antibiotics for the H. Pylori infection. He was the first to definitively prove that this bacterial infection caused gastritis. Although this particular experiment did not prove that H. Pylori caused ulcers, it's now been shown by other researchers.
In fact, now scientists know that H. Pylori bacteria is found in the stomach of about 50% of the world's population, but in most people it doesn't cause much of an issue; 80% of people infected don't have any symptoms and it may actually help protect against other diseases such as acid reflux and Barrett's esophagus. However, of those infected, they have a 10-20% lifetime risk of developing an ulcer and a 1-2% risk of developing stomach cancer. What this means is that eliminating H. Pylori by antibiotics can help treat the ulcer, and can also decrease the risk of stomach cancer.
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Dr. Cathy Seiler is the Program Manager for the tissue biorepository at St. Joseph's Hospital and Barrow Neurological Institute. She has her BA in Biochemistry and Molecular Biology from Boston University and PhD in the Biological Sciences from Cold Spring Harbor Laboratory. Her research and teaching focuses on genetics, cancer, and personalized medicine. Find her on Facebook at www.facebook.com/thingsitellmymom