Background and Research on Helicobacter pylori

Hyperlyser/Helicobacter pylori Project

Background

Peptic ulcer disease is a painful and debilitating condition, which has been estimated to affect 1 in 10 people in developed countries at some time in their lives. A principle cause of this condition is now widely accepted to be infection with Helicobacter pylori, a spiral shaped bacterium, which lives beneath the mucus layer of the stomach in affected individuals.

Helicobacter pylori infection is believed to be the most common infectious disease in the world, estimated to affect 60 % or more of the population in developing countries, and 40 % in Europe and America, infection being more likely with increased age.

Transmission is believed to be principally via faecal-oral contact, possibly in childhood, or through ingestion of contaminated food or fluids.

The bacterium survives in the highly acidic environment of the stomach because it has an enzyme, urease, which converts urea – a naturally occurring body product, into ammonia, which neutralizes the stomach acids and acts as a protective sheath for the organism. After entering the stomach, the bacterium enters the mucus layer and attaches itself to the stomach cells beneath. Chemicals released by the bacterium weaken the protective mucus layer, and can damage the underlying stomach cells. The body attempts to fight the infection by releasing white blood cells and other products into the stomach to attack the bacterium, but these cannot easily penetrate the mucus layer, and instead cause inflammation of the stomach tissue (gastritis).

Importance of Helicobacter pylori detection

Helicobacter pylori infection is strongly associated with gastritis, and with the incidence of duodenal and gastric ulcers. There is also evidence that infection with the bacterium may have some role in the development of gastric cancers.

The major disease caused by Helicobacter pylori infection is gastritis, which may produce feelings of discomfort, nausea and sometimes a burning sensation in the upper abdomen after meals. However, not all infected individuals will show symptoms. If this condition remains untreated for a period of several years, the stomach tissue may become abnormal and pre-cancerous. Treatment to eradicate Helicobacter pylori infection will often resolve the gastritis.

A small proportion of Helicobacter pylori positive individuals go on to develop peptic ulcers, although the vast majority does not. The reasons why some individuals are susceptible are not known, although variations in the strain of bacterium involved, differences in individual abilities to fight infection, and other factors such as age, are thought to be involved. Strong evidence for the link with peptic ulcer disease is the clinical observation that, after taking account of other factors contributing to peptic ulcer disease, such as the use of non-steroidal anti-inflammatory drugs, about 60 – 80 % of people with gastric ulcers are Helicobacter pylori positive. In the case of duodenal ulcers, the correlation is even higher, with over 90 % of individuals being found to be Helicobacter pylori positive.

For patients diagnosed with peptic ulcer disease, screening for Helicobacter pylori is normally a first priority, followed by eradication therapy where infection is confirmed. Although simple treatments for peptic ulcer disease based around reducing stomach acidity, are generally effective in eliminating ulcers, recurrence rates can be high if the underlying Helicobacter pylori infection is not dealt with. Consequently, for patients with confirmed peptic ulcer disease and Helicobacter pylori infection, treatment consists of both acid suppression, and anti-microbial drugs to eliminate the infection.

Diagnosis of Helicobacter pylori infection

There are at present several ways in which Helicobacter pylori infection may be detected. Tests may involve taking a breath sample (C13 or C14 urea breath test), a blood sample (serology) or a tissue sample of the stomach lining (endoscopy and biopsy). Each of these tests has some feature (expense, reliability, use of radio-active materials, invasive surgery), which has prevented extensive screening for Helicobacter pylori infection to be carried out.

C13 and C14 urea breath test

These procedures can be carried out in a doctor’s surgery. In these tests, the patient is given a drink containing a small amount urea labeled with an isotope of carbon (C13 or C14). If the patient is infected, the urease enzyme of the bacterium converts the urea into bicarbonate and ammonium ions. The bicarbonate is absorbed into the bloodstream, and is then expelled via the lungs as carbon dioxide. Breath samples are then taken and tested for the presence of labeled carbon dioxide. The C13 test requires the use of an expensive detector, and the breath samples will usually be sent to an outside laboratory for analysis. This test is therefore quite expensive and it may take several days before the results are available. The C14 test uses a simpler and cheaper detecting system, and results can be quickly obtained. However C14-urea is a radio-active material, and although the radiation received is a tiny fraction that obtained from natural sources in a year, patients may be unwilling to use this procedure.

Endoscopy and biopsy

In this procedure the patient swallows a narrow, flexible tube. This allows the person performing the endoscopy to visually examine the œasophagus, stomach and duodenum of the patient. Several small tissue samples are taken, and the presence of the bacterium is determined by laboratory testing these biopsy samples. Testing may be by staining (histology), detecting the presence of the enzyme urease present in Helicobacter pylori (CLOtest), or by culturing the bacterium. This process is expensive, requiring a short surgical procedure, with subsequent laboratory testing of tissue samples. Endoscopy is an invasive procedure, and can cause some discomfort for the patient. In addition, the tissue testing methods have variable degrees of accuracy, with false negative results being obtained in 5 – 15 % of cases, depending on the test used.

Serology

Several serological tests are available for the detection of Helicobacter pylori. A blood sample is taken, and laboratory tested for the presence of antibodies specific for the bacterium. Although these tests are relatively cheap and quick to perform, they are of limited use for individuals who have undergone treatment to eradicate Helicobacter pylori in the past, since antibodies can remain in the bloodstream for up to 3 years after the infection has been successfully treated.

Hyperlyser test for Helicobacter pylori infection

Hyperlyser Ltd is currently developing a new and simple test for Helicobacter pylori infection. This test will be :

• Non-invasive
• Inexpensive
• Carried out in a doctor’s surgery, bed-side or out-patient setting
• Rapid, with results obtained in minutes
  

The test involves taking breath samples using a hand held device incorporating a sensor unit. In contrast to the breath tests currently in use, patients are not required to swallow C13 or C14 labeled urea. The sensor is designed to detect the elevated levels of ammonia gas in the breath of infected individuals, produced by the breakdown of urea by Helicobacter pylori. Positive or negative test results are given about a minute after testing, by a display on the top of the unit. The sensor unit is in the form of a disposable cartridge, designed for single use.

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