1. Department of Medical-Surgical Specialties, A.O.U. Policlinico-Vittorio Emanuele, University of Catania, 95100 Catania, Italy
2. Division of Infectious Diseases, Department of Clinical and Molecular Biomedicine, Garibaldi Nesima Hospital, University of Catania, 95125 Catania, Italy
3. Department G.F. Ingrassia, Section of Anatomic Pathology, University of Catania, 95100 Catania, Italy
4. Department of Microbiology and Immunology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19115, USA