Use of colicin M or a derivative thereof for preventing or reducing contamination of an object with enterohaemorrhagic E. coli (EHEC), wherein said object is contacted with said colicin M or said derivative; wherein said colicin M or its derivative has an N-terminal translocation domain as follows: the N-terminal translocation domain has amino acid residues 1 to 35 of SEQ ID NO: 1, or has 1 amino acid substitution, insertion, addition or deletion compared to amino acid residues 1 to 35 of SEQ ID NO: 1, or has an amino acid sequence identity of at least 97 % to the N-terminal translocation domain of SEQ ID NO: 1, or has an amino acid sequence similarity of at least 97 % to the N-terminal translocation domain SEQ ID NO: 1; said colicin M or its derivative comprises a central receptor-binding domain as follows: the receptor-binding domain has residues 36 to 140 of colicin M of SEQ ID NO: 1, or has a domain having from 1 to 3 amino acid substitutions, insertions, additions or deletions compared to residues 36 to 140 of SEQ ID NO: 1, or has an amino acid sequence identity of at least 97 % to the receptor-binding domain of SEQ ID NO: 1, or has an amino acid sequence similarity of at least 97 % to the receptor-binding domain SEQ ID NO: 1; and said colicin M or its derivative comprises a C-terminal activity domain as follows: the activity domain is of residues 141 to 271 of SEQ ID NO: 1, or the activity domain has from 1 to 5 amino acid residue substitutions, insertions, additions or deletions compared to amino acid residues 141 to 271 of SEQ ID NO: 1, or the activity domain has an amino acid sequence identity of at least 97% to the activity domain of SEQ ID NO: 1; wherein contamination of an object with any one or all of the following E. coli serotypes is prevented or reduced: serotype O26:H11, serotype O45:H2, serotype 0103:H11, serotype O111:H8, serotype O157:H7, serotype O145:NM, and serotype O104:H4, and wherein the use does not comprise treatment of the human or animal body by surgery or therapy. said colicin M or its derivative has an N-terminal translocation domain as follows: the N-terminal translocation domain has amino acid residues 1 to 35 of SEQ ID NO: 1, or has 1 amino acid substitution, insertion, addition or deletion compared to amino acid residues 1 to 35 of SEQ ID NO: 1, or has an amino acid sequence identity of at least 97 % to the N-terminal translocation domain of SEQ ID NO: 1, or has an amino acid sequence similarity of at least 97 % to the N-terminal translocation domain SEQ ID NO: 1; the N-terminal translocation domain has amino acid residues 1 to 35 of SEQ ID NO: 1, or has 1 amino acid substitution, insertion, addition or deletion compared to amino acid residues 1 to 35 of SEQ ID NO: 1, or has an amino acid sequence identity of at least 97 % to the N-terminal translocation domain of SEQ ID NO: 1, or has an amino acid sequence similarity of at least 97 % to the N-terminal translocation domain SEQ ID NO: 1; said colicin M or its derivative comprises a central receptor-binding domain as follows: the receptor-binding domain has residues 36 to 140 of colicin M of SEQ ID NO: 1, or has a domain having from 1 to 3 amino acid substitutions, insertions, additions or deletions compared to residues 36 to 140 of SEQ ID NO: 1, or has an amino acid sequence identity of at least 97 % to the receptor-binding domain of SEQ ID NO: 1, or has an amino acid sequence similarity of at least 97 % to the receptor-binding domain SEQ ID NO: 1; and the receptor-binding domain has residues 36 to 140 of colicin M of SEQ ID NO: 1, or has a domain having from 1 to 3 amino acid substitutions, insertions, additions or deletions compared to residues 36 to 140 of SEQ ID NO: 1, or has an amino acid sequence identity of at least 97 % to the receptor-binding domain of SEQ ID NO: 1, or has an amino acid sequence similarity of at least 97 % to the receptor-binding domain SEQ ID NO: 1; and said colicin M or its derivative comprises a C-terminal activity domain as follows: the activity domain is of residues 141 to 271 of SEQ ID NO: 1, or the activity domain has from 1 to 5 amino acid residue substitutions, insertions, additions or deletions compared to amino acid residues 141 to 271 of SEQ ID NO: 1, or the activity domain has an amino acid sequence identity of at least 97% to the activity domain of SEQ ID NO: 1; wherein contamination of an object with any one or all of the following E. coli serotypes is prevented or reduced: serotype O26:H11, serotype O45:H2, serotype 0103:H11, serotype O111:H8, serotype O157:H7, serotype O145:NM, and serotype O104:H4, and wherein the use does not comprise treatment of the human or animal body by surgery or therapy. the activity domain is of residues 141 to 271 of SEQ ID NO: 1, or the activity domain has from 1 to 5 amino acid residue substitutions, insertions, additions or deletions compared to amino acid residues 141 to 271 of SEQ ID NO: 1, or the activity domain has an amino acid sequence identity of at least 97% to the activity domain of SEQ ID NO: 1; wherein contamination of an object with any one or all of the following E. coli serotypes is prevented or reduced: serotype O26:H11, serotype O45:H2, serotype 0103:H11, serotype O111:H8, serotype O157:H7, serotype O145:NM, and serotype O104:H4, and wherein the use does not comprise treatment of the human or animal body by surgery or therapy.