1. Bone Marrow Transplantation Unit, Haematology Department, G. Papanicolaou Hospital, 57010 Thessaloniki, Greece
2. Second Propedeutic Department of Internal Medicine, Hippocration Hospital, Aristotle University of Thessaloniki, 54642 Thessaloniki, Greece
3. Department of Microbiology, Medical School, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece