1. Laboratory for Control and Monitoring of the Antibiotic Resistance, National Centre for Infectious and Parasitic Diseases, 26 Yanko Sakazov Blvd, 1504 Sofia, Bulgaria
2. Nadezhda Paradise Medical Center, 1330 Sofia, Bulgaria
3. Department of Cell and Developmental Biology, Faculty of Biology, Sofia University “St. Kliment Ohridski”, 1504 Sofia, Bulgaria
4. Department of Gastroenterology, University Hospital Lozenetz, Sofia, Medical Faculty, Sofia University “St. Kliment Ohridski”, 1407 Sofia, Bulgaria
5. Department of Gastroenterology, University Hospital Heart and Brain, 5804 Pleven, Bulgaria
6. Medical Faculty, Sofia University St. Kliment Ohridski, Kozyak 1 str., 1407 Sofia, Bulgaria