What Is an Ulcer: Causes, Symptoms and Helicobacter pylori

What Is an Ulcer: Causes, Symptoms and Helicobacter pylori
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  • 0:05 Human Guinea Pig
  • 1:54 Helicobacter Pylori
  • 2:53 Gastric Ulcers
  • 5:29 Catching Helicobacter
  • 6:12 Diagnosis and Treatment
  • 7:16 Lesson Summary
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Instructor: Angela Hartsock

Angela has taught college Microbiology and has a doctoral degree in Microbiology.

Once thought to be caused by a stressful life and spicy foods, stomach ulcers have been causing severe pain in people for years. In this lesson, we will look at the bacteria Helicobacter pylori, now confirmed to be the real cause of most stomach ulcers.

Human Guinea Pig

Throughout history, scientists, philosophers and other great thinkers have made some outrageous claims. Copernicus claimed that the earth revolved around the sun, not the other way around. Darwin claimed that all organisms evolved from previous organisms through natural selection. These two men were persecuted in their time but later vindicated when their theories proved to be right. You are probably familiar with these famous men, but let me introduce you to two more whose work was considered no less heretical but is much more recent.

In the 1980s, two Australian gastroenterologists, Barry Marshall and Robin Warren, identified a unique species of bacteria in the stomach lining of patients with gastric ulcers. They hypothesized that the ulcer pain and inflammation was caused by this bacteria and not stress or diet as previously thought. The medical and scientific communities refused to believe this new idea. Even as experimental evidence mounted, most people were skeptical.

In 1984, Barry Marshall decided he had to do something drastic in an attempt to convince people: he drank a solution of his ulcer-causing bacteria! Within two weeks, Marshall started showing symptoms of stomach inflammation, a classic precursor to developing a full-blown ulcer. This bold experiment helped revolutionize the way doctors look at stomach ulcers.

In the end, Marshall and Warren were vindicated when, in 2005, they were awarded the Nobel Prize in Physiology or Medicine for their discovery that Helicobacter pylori causes ulcers. So, let's continue our discussion of ulcers by looking at the bacteria now widely accepted to be responsible: Helicobacter pylori.

Helicobacter pylori

Helicobacter pylori is a Gram-negative, spiral-shaped bacteria that is found in the stomach and small intestine of humans. 'Gram-negative' refers to the thin layer of peptidoglycan and the presence of an outer membrane in the Helicobacter cell wall.

Helicobacter is present in the gut of about half the world's population. The human stomach naturally houses up to 200 different species of bacteria, but Helicobacter is often the one present in the largest numbers. For the majority of people, Helicobacter will be a silent rider, never causing any illness. In these people, there is a kind of stalemate between the immune system and the Helicobacter. The immune system is able to keep Helicobacter in check, preventing development of symptoms, but Helicobacter is able to survive and persist. In about 2% of people, the bacteria eventually get ahead of the immune system and can cause a very painful stomach lesion called a gastric ulcer.

Gastric Ulcers

A gastric ulcer is a painful lesion caused by erosion of the mucosal layer of the stomach. An estimated 25 million Americans will experience an ulcer in their lifetime. These people experience intense abdominal pain that they can't seem to alleviate with antacids, drinking or eating. Some patients also become nauseated and vomit. In severe cases, ulcers can bleed, leading to anemia.

Before Marshall and Warren, doctors believed that ulcers were caused by an excess of stomach acid. Things like stress, spicy food, smoking and alcohol would cause an increase in acid production. Doctors reasoned that ulcers were a result of the excess acid damaging the stomach lining. Treatment was limited to antacid medications, which were rarely effective.

So, how does a tiny bacterium cause stomach ulcers?

First, we need to understand the structure of the stomach. The stomach is a hollow, J-shaped organ responsible for storing, mixing and some digestion of food. The wall of the stomach is composed of four layers of tissue. The mucosa is the layer that lines the inside of the stomach. The mucosa contains many glands that produce hydrochloric acid, digestive enzymes and mucous, releasing these compounds into the stomach.

The hydrochloric acid keeps the pH of the stomach strongly acidic, between a pH of one and two. This extreme pH would damage the stomach lining if the acid was able to remain in contact with the cells for a long time. The mucous glands continuously pump out mucous, which coats the mucosa, protecting it from the acid.

Helicobacter is able to survive in acidic conditions, but the stomach is a little too acidic for Helicobacter to survive for long. The bacteria first penetrate through the mucous layer of the stomach. Helicobacter attaches itself to the mucosa and begins to break down urea that is already present in the stomach, creating ammonia as a waste product. Ammonia is basic and raises the pH around the bacteria to a more survivable level.

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