1. Department of Medical Microbiology, Faculty of Medicine, Medical University of Sofia, 2 Zdrave Street, Sofia 1431, Bulgaria;
2. Laboratory of Microbiology, Department of Military Epidemiology and Hygiene, Military Medical Academy, Sofia, Bulgaria;
3. Department of Genetics, Faculty of Biology, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria;
4. Department of Medical Microbiology, Faculty of Medicine, Medical University of Sofia, Sofia, Bulgaria