Inclusion Criteria:
- willingness to participate (based on the signed informed consent form);
- age older than 12 y.o. (for subjects younger than 18 y.o. written informed consent of a legal representative was obligatory);
- availability of demographic data and medical history, including previous treatment for H.pylori infection
For subjects of "treatment-naïve" group:
- no previous treatment for H.pylori infection in the anamnesis;
- at least 6 weeks after previous use of any antimicrobial agents for any reason;
- at least 2 weeks' time frame free of use of proton pump inhibitors, other anti-secretory agents and bismuth preparations.
For "Previously treated" group of subjects:
- infection caused by H.pylori established earlier and
- not less than 6 weeks after the end of eradication therapy with at least 2 antibiotics and a proton pump inhibitor for at least 7 days, based on a patient's report
Exclusion Criteria:
- history of surgery on chest, stomach, gut (excluding appendectomy or laparoscopic cholecystectomy performed more than 6 month before the enrolment);
- advanced stage of chronic obstructive pulmonary disease,
- allergies to citruses,
- pregnant and breastfeeding women.