H. pylori infection

Helicobacter pylori (H. pylori for short) is the name of bacteria that infect the human stomach lining. Because it can last a long time, it is called a chronic infection. Chronic H. pylori infection is estimated to affect half or more of the world’s population. In 2005, Barry Marshall and Robin Warren were awarded the Nobel Prize for their identification of this organism in 1982.

When people get H. pylori infection, the bacteria irritate the stomach lining, causing inflammation called gastritis. The gastritis can be mild or severe, and it may or may not make people feel sick. At first, some people may get stomach problems that stop after a few days. Often, the infection lasts many years, possibly even a life time, without symptoms. As a result, most people with H. pylori don’t even realize they have it.

Some people with chronic H. pylori infection develop long-lasting symptoms, such as stomach pain, nausea or vomiting, and a small percent develop serious diseases. These diseases include stomach ulcers and, in rare instances, stomach cancer. It has been estimated that among people with H. pylori infection, about 10% will develop a stomach ulcer in their lifetime and about 1% or less will develop stomach cancer. Many things other than H. pylori can cause stomach problems, so a medical exam is needed to find out the most likely cause of long-lasting symptoms.

People get H. pylori infection most often during childhood. Unfortunately, scientists are still not quite sure how people get infected. It most likely happens when a person comes in direct contact with an infected person’s germs, especially if that person is sick with vomiting or diarrhea.

Although humans are the only known source of H. pylori infection, scientists have not been able to confirm or rule out environmental sources of H. pylori infection, for example, water sources. Previous studies have detected the presence of H. pylori in water, but it is unclear if the bacteria are alive and capable of infecting someone. Because of this uncertainty, public health control measures for H. pylori have not been developed.

To see if someone has H. pylori, available tests can be divided into those that detect the bacteria, or a part of the bacteria such as a gene sequence or protein; a substance secreted by the bacteria; or specific antibodies produced as an immune response to the bacteria.

Tests that detect the bacteria require endoscopy, for which doctors put a thin tube down your throat into your stomach and take biopsies, which are very tiny samples of stomach tissue. These tests include:

  • Histopathology — For this test, biopsy slices are made into slides so a pathologist can examine them under a microscope to see if H. pylori organisms are visible. Pathologists uses a score to indicate how much H. pylori they see in your stomach tissue.
  • Culture — Because bacteria are living organisms, they can be made to grow in laboratories under the right conditions. A culture test provides conditions that encourage the bacteria to grow from stomach biopsies. If H. pylori organisms grow from your stomach tissue, this means you have H. pylori living in your stomach.

Tests that detect a part of the bacteria or a substance secreted by it include:

  • Breath Test - For this test, you drink a solution containing a naturally occurring substance called urea. The most common breath test uses 13C-urea, which contains an extra amount of a particular carbon molecule that serves as a tracer. If you have H. pylori in your stomach, it will secrete a substance that breaks down the urea, releasing CO2, which gets exhaled in your breath. We can measure the tracer molecule in samples of your breath. This test gives us an approximate idea of how much H. pylori is in your stomach.
  • Stool Test - When H. pylori lives in your stomach, it can pass through your digestive tract the same way food does. We can test samples of stool (feces) to see if it contains H. pylori DNA or proteins, and if so, this tells us you have H. pylori living in your stomach.

A test that detects specific antibiodies produced as an immune response to the bacteria:

  • Blood Test - If we take a sample of blood, we can test for antibodies that are specific to H. pylori. If you have these antibodies, we know that you have, at some point in your life, been infected with H. pylori. Antibodies sometimes last a long time after the infection has cleared, so the presence of antibodies does not tell us if you currently have H. pylori, or had it in the past. If you don't have antibodies, we cannot be sure that you were not infected in the past.

In order to treat H. pylori, combinations of drugs are typically used. The best treatments require 3-4 drugs for 7-14 days. However, H. pylori is a tricky organism to treat and across most of Canada around 80% of people treated will be cured of the infection. This means for about 2 of every 10 people the treatment does not work. In areas where H. pylori infection is more common, treatment failure is also more common. In such places, treatment for H. pylori is successful for even fewer than 80% of people treated.