title: Natural antibiotic resistance and contamination by antibiotic resistance determinants: the two ages in the evolution of resistance to antimicrobials.
authors.affiliation: Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas Madrid, Spain.
authors.forename: José L
authors.initials: JL
authors.lastname: Martínez