1. Oncology Department, P & A Kyriakou Children's Hospital, Athens, Greece
2. Department of Microbiology, National and Kapodistrian University of Athens (NKUA), School of Medicine, Athens, Greece
3. Second Department of Paediatrics, National and Kapodistrian University of Athens (NKUA), School of Medicine, P. and A. Kyriakou Children's hospital, Athens, Greece