1. Section of General Surgery, Department of Propedeutics of Surgical Diseases, Faculty of Medicine, Medical University of Plovdiv, 4001 Plovdiv, Bulgaria
2. First Clinic of Surgery, University Hospital St. George, 4001 Plovdiv, Bulgaria
3. Department of Medical Microbiology and Immunology “Prof. Dr. Elissay Yanev”, Faculty of Medicine, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria
4. Laboratory of Microbiology, University Hospital St. George, 4002 Plovdiv, Bulgaria