1. Clinical Microbiology and Infectious Diseases Department, Hospital General Universitario Gregorio Marañón, Madrid, Spain
2. CIBER de Enfermedades Respiratorias (CIBERES CB06/06/0058), Madrid, Spain
3. Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain
4. Bruker Daltonik GmbH, Bremen, Germany
5. Medicine Department, School of Medicine, Universidad Complutense de Madrid, Madrid, Spain