To an extent varying according to populations, the pathogen Helicobacter pylori is present in the stomach of people, causing no problem at all in most of the cases. However, in some cases it can cause chronic gastritis, ulcer, and is associated with the development of gastric cancer and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Therefore, if deemed necessary by the physician, it is recommended to eradicate the bacterium; this is achieved with an intensive therapy - not without side effects - using a combination of antibiotics and other medicines. However, the eradication therapy is not always successful because the bacterium may be resistant to the antibiotic, which becomes evident only after the treatment. Further analysis of the tissue sample can prevent this; the bacterium’s antibiotic resistance (clarithromycin) can be detected with a genetic test. This provides information for the physician to use a different combination for the treatment thus avoiding the side effects and costs of an ineffective treatment. The test is performed using the tissue block of the gastric biopsy.