1. University Hospital "Prof. Iv. Kirov”, Medical University of Sofia, Sofia, Bulgaria
2. Department of Microbiology, National Center of Infectious and Parasitic Diseases, Sofia, Bulgaria
3. University Hospital "Queen Joanna - ISUL", Medical University of Sofia, Sofia, Bulgaria
4. Department of Microbiology and Immunology “Prof. Dr. Elissay Yanev”, Faculty of Pharmacy, Medical University of Plovdiv, Plovdiv, Bulgaria
5. Laboratory of Microbiology, “St. George” University Hospital, Medical University of Plovdiv, Plovdiv, Bulgaria