[1] ASO S Giovanni Battista, CPO Piemonte, Unite Canc Epidemiol, I-10123 Turin, Italy
[2] ASO S Giovannii Battista, Microbiol Unit, I-10126 Turin, Italy
[3] Vrije Univ Amsterdam, Med Ctr, Dept Pathol, NL-1081 HV Amsterdam, Netherlands
[4] Univ Turin, CERMS & CPO Piemonte, Unit Canc Epidemiol, Turin, Italy
[5] Int Agcy Res Canc, F-69008 Lyon, France