How diagnostic tools support patient management, from infection screening to bacterial eradication

A feeling of indigestion or bloating, as well as nausea and loss of appetite. These are rather general symptoms with multiple possible causes, often leading patients to consult their doctor.

But what if the cause were a Helicobacter pylori infection?

This bacterium, which may be responsible for these symptoms, is both fascinating and formidable. Fascinating because it is able to survive in the hostile environment of the stomach through the activity of an enzyme called urease, and because it is closely linked to a remarkable story in medical history that earned Professors Warren and Marshall the Nobel Prize in 2005. Formidable because the infection it causes can develop into serious conditions, such as chronic gastritis, peptic ulcer disease and gastric adenocarcinoma.

Why test for an H. pylori infection?

For general practitioners, it is important to consider H. pylori infection in patients presenting with gastrointestinal symptoms. This is particularly relevant in patients with unexplained dyspepsia, iron-deficiency anaemia, or a personal or family history of peptic ulcer disease.

The Maastricht VI/Florence Consensus recommends a screen-and-treat strategy for patients under 50 years of age with dyspeptic symptoms and no alarm signs. In Switzerland, this bacterium is present in 10–20% of the population, and its prevalence increases with age.

How can H. pylori infection be detected?

The range of analytical tests is broad. Some tests are used to detect the infection, others to monitor eradication, and others to determine antibiotic resistance. Tests can be classified as invasive, requiring analysis of a gastric biopsy, or non-invasive. Let us start with the latter.

Serology, which detects antibodies in the blood, is a simple test that can identify patients who have been in contact with the bacterium. However, it cannot distinguish between active and past infection and is not suitable for monitoring eradication.

The urea breath test is considered the gold standard among non-invasive tests, although it requires particular care during the collection of the exhaled air sample. It is useful both as a screening test and for therapeutic monitoring. Before performing the test, it is important to ensure that the patient has discontinued all treatments, including antibiotics and proton pump inhibitors, for several weeks in order to avoid the risk of false-negative results.

An alternative to the breath test is the detection of H. pylori antigens in stool. Although slightly less sensitive than the breath test, it has the advantage of being less restrictive regarding treatment discontinuation.

How can we know whether the bacterium is sensitive to antibiotics?

Antibiotic susceptibility testing is particularly useful in cases of treatment failure, which may be related to resistance to the antibiotic clarithromycin. The only way to perform this is by analysing gastric biopsies. After culture, an antibiotic resistance test is carried out on the colonies that have grown.

As cultures sometimes remain sterile, an alternative solution is molecular biology testing to detect antibiotic resistance genes directly from the biopsy. This test can also be performed on material that has already been processed for histology. This highly sophisticated approach, however, only allows testing for a limited number of antibiotics, including clarithromycin, fluoroquinolones and metronidazole.

Conclusion

H. pylori infection is common. Thanks to a broad range of diagnostic tests, physicians can detect infections early, initiate effective treatment and confirm therapeutic success.

Author: Dr Giuseppe Togni, Scientific Director of Microbiology at Unilabs.