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.