A method to modify an inorganic substrate intended to impart antimicrobial properties thereto whereby, in one or more steps, groups having intrinsic antimicrobial properties or groups capable of releasing species having antimicrobial properties are grafted onto a surface of said substrate, grafting being conducted via an organophosphorus coupling agent, characterized in that: - the substrate is selected from among metals, metal carbonates and metal phosphates; - the organophosphorus coupling agent is selected from among phosphonic acids and phosphonates of formula RPO 2, bis-phosphonates of formula RR'[PO 2] 2, phosphinic acids and phosphinates of formula RR'PO, monoalkyl phosphates of formula ROPO 2 and dialkyl phosphates of formula (R'O)PO, wherein: • X is a hydrogen atom or a group selected from among metal ions, ammonium ions, alkyl or aryl groups having 1 to 6 carbon atoms and trialkylsilyl groups having 1 to 6 carbon atoms; • R is an organic group selected from among: - groups having intrinsic antimicrobial properties; - groups capable of releasing species having antimicrobial properties selected from among groups releasing nitrogen monoxide and groups releasing carboxylic acids; - R" groups which, after modification, have intrinsic antimicrobial properties or are capable of releasing species having antimicrobial properties, said R groups being selected from among -(CH 2) n -SH, -(CH 2) n -CN, -(CH 2) n -NH 2, -(CH 2) n -[NH-(CH 2) n] n -NH 2, -(CH 2) n -NMe 2, -(CH 2) n -Hal groups, Hal being a halogen atom, n is between 1 and 20, n is between 1 and 5, n is between 1 and 10; R' is a hydrogen atom, a hydroxyl group or an organic group meeting the definition of said R groups; - the organophosphorus coupling agent is bonded to the surface of the substrate via M-O-P bonds wherein M is the metal of the substrate, said bonds being derived from condensation of the P-OX groups and/or from coordination of the phosphoryl groups P=O. - the substrate is selected from among metals, metal carbonates and metal phosphates; - the organophosphorus coupling agent is selected from among phosphonic acids and phosphonates of formula RPO 2, bis-phosphonates of formula RR'[PO 2] 2, phosphinic acids and phosphinates of formula RR'PO, monoalkyl phosphates of formula ROPO 2 and dialkyl phosphates of formula (R'O)PO, wherein: • X is a hydrogen atom or a group selected from among metal ions, ammonium ions, alkyl or aryl groups having 1 to 6 carbon atoms and trialkylsilyl groups having 1 to 6 carbon atoms; • R is an organic group selected from among: - groups having intrinsic antimicrobial properties; - groups capable of releasing species having antimicrobial properties selected from among groups releasing nitrogen monoxide and groups releasing carboxylic acids; - R" groups which, after modification, have intrinsic antimicrobial properties or are capable of releasing species having antimicrobial properties, said R groups being selected from among -(CH 2) n -SH, -(CH 2) n -CN, -(CH 2) n -NH 2, -(CH 2) n -[NH-(CH 2) n] n -NH 2, -(CH 2) n -NMe 2, -(CH 2) n -Hal groups, Hal being a halogen atom, n is between 1 and 20, n is between 1 and 5, n is between 1 and 10; R' is a hydrogen atom, a hydroxyl group or an organic group meeting the definition of said R groups; • X is a hydrogen atom or a group selected from among metal ions, ammonium ions, alkyl or aryl groups having 1 to 6 carbon atoms and trialkylsilyl groups having 1 to 6 carbon atoms; • R is an organic group selected from among: - groups having intrinsic antimicrobial properties; - groups capable of releasing species having antimicrobial properties selected from among groups releasing nitrogen monoxide and groups releasing carboxylic acids; - R" groups which, after modification, have intrinsic antimicrobial properties or are capable of releasing species having antimicrobial properties, said R groups being selected from among -(CH 2) n -SH, -(CH 2) n -CN, -(CH 2) n -NH 2, -(CH 2) n -[NH-(CH 2) n] n -NH 2, -(CH 2) n -NMe 2, -(CH 2) n -Hal groups, Hal being a halogen atom, n is between 1 and 20, n is between 1 and 5, n is between 1 and 10; - groups having intrinsic antimicrobial properties; - groups capable of releasing species having antimicrobial properties selected from among groups releasing nitrogen monoxide and groups releasing carboxylic acids; - R" groups which, after modification, have intrinsic antimicrobial properties or are capable of releasing species having antimicrobial properties, said R groups being selected from among -(CH 2) n -SH, -(CH 2) n -CN, -(CH 2) n -NH 2, -(CH 2) n -[NH-(CH 2) n] n -NH 2, -(CH 2) n -NMe 2, -(CH 2) n -Hal groups, Hal being a halogen atom, n is between 1 and 20, n is between 1 and 5, n is between 1 and 10; - the organophosphorus coupling agent is bonded to the surface of the substrate via M-O-P bonds wherein M is the metal of the substrate, said bonds being derived from condensation of the P-OX groups and/or from coordination of the phosphoryl groups P=O.