1. Department of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, 00161 Rome,1 and
2. Department of Infectious Diseases, Microbiology and Molecular Biology, Arcispedale S. Maria Nuova, 42100 Reggio Emilia,2 Italy, and
3. Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, California 956163