Helicobacter Pylori detection and elimination

By: Dr. Natalia Loaiza Díaz, M.D.

Medical Microbiologist, Clinical Pathology Leader.  Laboratorio Clínico Hematológico S.A.S.

Published: April 25, 2023

¿How to diagnose H. pylori infection?

The first thing to do is to consult when symptoms of gastritis are present (pain or burning in the upper abdomen, accompanied or not by nausea, vomiting, a feeling of fullness or lack of appetite), when a family member or partner has been informed that he/she has the infection, or in cases of unexplained iron deficiency anemia or idiopathic thrombocytopenic purpura. According to the findings of the physician during the interview and physical examination, he/she will indicate the test that he/she considers pertinent.

Currently, several types of tests are available in the field to approach the diagnosis of this infection. Some of them require gastric tissue obtained by biopsy during digestive endoscopy procedures; therefore, they are considered invasive. Others look for “clues” to the microorganism indirectly, i.e. without reaching the tissue, and are therefore considered non-invasive.

For the results of both groups of tests to be optimal and to avoid false results, it is essential for the patient to stop taking drugs such as antibiotics (four weeks before) and proton pump inhibitors (two weeks before), except for serum (blood) antibody detection tests, which do not require this.

Non-invasive tests:

  • Urea breath test 3-6,8,10.

This test is considered the best among the non-invasive methods to make the diagnosis of H. pylori infection and is available at the Hematológico. It is useful both for initial diagnosis and to confirm whether treatment was successful once it has been completed.

The test measures the activity of the urease enzyme produced by the bacteria to establish itself in the stomach. It consists of administering orally to the patient (on an empty stomach) a dilution containing a type of urea labeled with carbon 13 (13C-urea), a non-radioactive isotope of carbon. If H. pylori is present, its enzyme urease will hydrolyze or break down 13C-urea into ammonia and bicarbonate. The latter will be 13C-labeled and will pass into the circulation, travel to the lungs and exit on exhalation as 13C-labeled carbon dioxide (13CO2).

Subsequently, a sample of exhaled air (or breath) is taken from the patient and the 13CO2 released is quantified in comparison to that of a breath sample taken before ingesting the 13C-urea solution, using specialized equipment that allows 13CO2 to be separated from the CO2 that is normally exhaled.

  • Detection of H. pylori antigen in fecal material 3-5,8,9,11.
This is another non-invasive test, available at Hematológico through the network of allied laboratories. Like the previous one, it is useful for initial diagnosis and to check therapeutic success. For this, techniques such as enzyme immunoassays or immunochromatography are used to indirectly determine the presence or absence of the microorganism in stool samples by means of antibodies directed against H. pylori contained in the test, which will bind specifically to the antigens of the bacterium and thus reveal whether it is present in the patient’s sample.
  • Detection of IgA, IgM and IgG antibodies against H. pylori 3-5,8,9,11.

This non-invasive technique is available at the Hematológico through allied laboratories and allows us to know if the person has been in contact with the microorganism previously, since it measures immunoglobulin (Ig) antibodies of different classes (IgA, IgM and IgG) produced by the patient’s immune response against H. pylori. The sample used is serum (blood) obtained by venipuncture.

The antibodies measured in this test do not allow differentiation between a past and an active infection, nor does their value relate to the severity of the infection. Furthermore, since they can remain in the blood for more than one year, they should not be used to determine whether the treatment was successful or not.

Invasive tests:

To perform these tests, the patient must first undergo an endoscopy procedure, which is usually performed under sedation. In this, in addition to appreciating with the help of a camera how the stomach mucosa is, biopsies can be taken. What is recommended by the Sydney system, a standardized method used worldwide for the classification of gastritis and the reporting of endoscopic and biopsy findings, in its 1994 updated version, is to take five tissue fragments or biopsies, as follows: two from the antrum, two from the body, and one from the incisura.

The above, with the aim of increasing the probability of detecting the microorganism and of timely detecting premalignant lesions, since the greater the amount of tissue seen under the microscope or sown in culture, the greater the probability of observing H. pylori or obtaining its colonies.

  • Histological examination.
This study, available in the anatomic pathology laboratory of the Hematológico, is the most important of the analyses to be performed on samples obtained by invasive methods. It consists of submitting the gastric tissue, which must be in bottles with buffered formalin provided by the laboratory, to a series of processes to preserve its structure and stain it with hematoxylin-eosin, Giemsa and Warthin-Starry silver stains, and sometimes with immunohistochemical stains. Once the assembly is ready, the stained slides are visualized under the light microscope to determine not only whether or not H. pylori is present in the tissue, but also active inflammation, changes in tissue architecture, cell shape and arrangement, among others, and finally to conclude whether or not there is infection, classify the gastritis and indicate whether there are changes associated with premalignant or malignant lesions.
  • Rapid urease test
It consists of subjecting a piece of a gastric biopsy to contact with a reagent containing urea and, using the presence of the urease enzyme of the microorganism in the sample, to appreciate a color change in the urea that is produced by the change in pH that is generated when the urease of H. pylori hydrolyzes urea into bicarbonate and ammonia. This test, available in the anatomic pathology laboratory of the Hematológico, has the advantage that the results are obtained quickly and can be used in the initial diagnosis, but not for follow-up treatment since a new biopsy would be necessary.
  • Helicobacter pylori culture
This method is considered the gold standard for diagnosing the infection. The test is offered in few centers since the characteristics of the microorganism require the use of special transport and culture media, and unusual procedures for processing, seeding of the samples and incubation of the culture media, to finally reach the point of value of this test which is the isolation of the bacteria, with the subsequent performance of antimicrobial susceptibility testing. In the Hematológico we directly culture the gastric tissue biopsies taken by the endoscopist and placed in the transport medium previously provided by the laboratory. Ideally, their processing and seeding in the culture media is done the same day the samples are taken. Subsequently, they are incubated in an atmosphere containing higher humidity and CO2 than usual, and observed periodically, waiting to observe from the fifth day onwards, a small dew that indicates that H. pylori is growing. Finally, starting from the colonies of the microorganism that have grown on the agar, tests are performed to confirm its identification and susceptibility to antimicrobials (antibiogram), which usually takes another three days. In this case, the bacterium is challenged against five antibiotics: amoxicillin, clarithromycin, metronidazole, levofloxacin and tetracycline, in order to determine in vitro whether it is sensitive or resistant to these agents.
  • Molecular tests for H. pylori detection 
Molecular biology techniques such as polymerase chain reaction (PCR) offer great advantages, since they are more sensitive than culture in detecting and identifying the microorganism in the sample, as well as some resistance genes, mainly for macrolides (such as clarithromycin) and fluoroquinolones (such as levofloxacin), and the result is obtained in a single day. This type of tests can be applied directly in tissue fragments (gastric biopsies), in bacterial colonies grown in culture, even in stool samples; however, in the country their availability is still scarce in clinical laboratories. PCR and other techniques such as NGS (next generation sequencing) are also used to study the presence of genes and mutations associated with greater virulence of the microorganism and greater severity of infection in certain cases and populations.
¿How can H. pylori infection be eliminated?
The treatment of this infection requires the combination of several drugs, such as proton pump inhibitors and antibiotics from different families (amoxicillin, clarithromycin or metronidazole), which must be taken for 14 days and continuously. This combination is called standard triple therapy and is recommended by international guidelines and the Colombian clinical practice guidelines for the diagnosis and treatment of H. pylori infection in adults, as the first line of treatment. Pharmacological treatment is often selected empirically; however, bearing in mind that from the moment the bacteria colonize the stomach until they trigger changes in the gastric tissue and cancer, many years elapse, and that the microorganism is known to have developed resistance to several of the antibiotics commonly used for its treatment, it is considered a good practice to perform culture or molecular tests to identify the bacteria and know its susceptibility profile before defining the treatment. This, with the aim of choosing the antibiotics to which it is sensitive and achieving greater therapeutic success.   Treatment failures are due to the growing resistance of H. pylori to antibiotics, but also to the lack of adherence to treatment by patients or to abandonment of treatment due to the discomfort or side effects it may cause. For this reason, it should be explained to the patient how important it is to complete treatment in order to eradicate the infection, prevent its complications, avoid further resistance to antibiotics and guarantee the success of subsequent treatments. Resistance rates of H. pylori to antimicrobials have been studied in a few regions of the country, finding variability. For amoxicillin, resistance is between 1.9% and 19.5%, for metronidazole between 72.0% and 97.6%, for macrolides (such as clarithromycin) between 13.6% and 63.1% (in Antioquia it is 18.8%), and for levofloxacin it reaches 27.3%. Resistance has also been found simultaneously to more than one family of antibiotics, even up to three (multi-resistance), which reinforces the recommendation that treatment should be prescribed based on the local epidemiology (if known) or based on the susceptibility profile of H. pylori to antimicrobials obtained in the antibiogram. At the end of drug therapy, clinical follow-up should be performed and eradication of the microorganism should be confirmed with non-invasive tests such as the 13C-urea breath test or fecal antigen detection. Given that a large part of humanity is a carrier of this infection and that its association with gastric cancer and other complications is clear, preventive, prophylactic and therapeutic strategies against H. pylori, such as vaccines, which achieve broad and long-term coverage, are of great interest. Studies are underway that still face the challenges of defining which portions of the microorganism to use, which route of administration is the best, how much protection they achieve and for how long they last.

In the Hematológico.

At Hematológico we have non-invasive diagnostic and follow-up tests performed on high-tech platforms, as well as standardized techniques for cytopathological analysis, culture, identification and susceptibility testing from gastric tissue samples, and a specialized medical team in both the areas of Microbiology and Anatomic Pathology, to ensure timely, accurate and integrated diagnoses, and to be an ally of gastroenterologists and endoscopists in the management of their patients. We are also working on the implementation of molecular methods, supported by scientists in the area, which we hope to have soon available to our entire medical community and patients.


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