About the Authors
Department of Public Health and Microbiology, University of Turin, Turin, Italy
Department of Clinical and Experimental Medicine, University of Piemonte Orientale, Novara, Italy
The authors have declared that no competing interests exist.
Conceived and designed the experiments: SL. Performed the experiments: GRG VDO MB DG AL. Analyzed the data: MDA GG MG. Wrote the paper: SL.