An in vitro or ex vivo method of killing, damaging or preventing the replication of bacteria comprising administering or applying a bacteriocin to said bacteria, wherein said bacteriocin and said bacteria are selected from: i) said bacteriocin is a peptide of less than 40 amino acids comprising an amino acid sequence selected from: MKFKFNPTGTIVKKLTQYEIAWFKNKHGYYPWEIPRC (SEQ ID NO:1 - EntK1) or a sequence with at least 90% sequence identity thereto, and said bacteriocin has antibacterial activity, and said bacteria is vancomycin-resistant E. faecium; ii) said bacteriocin is a truncated peptide of MLAKIKAMIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA (SEQ ID NO:2 - EntEJ97), consisting of the sequence: KAMIKKFPN PYTLAAKLTTYEI NWYKQQYGRYPWERPVA, AMIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, MIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, IKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, or KKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, or a sequence with at least 90% sequence identity to any of those sequences, and said bacteriocin has antibacterial activity, preferably MIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA (SEQ ID NO:3-EntEJ97short) or a sequence with at least 90% sequence identity thereto, and said bacteria is S. pseudointermedius and/or S. hemolyticus; and iii) said bacteriocin is a peptide of less than 40 amino acids comprising an amino acid sequence selected from: MKFKFNPTGTIVKKLTQYEINWYKQQYGRYPWERPVA (SEQ ID NO:4 - K1-EJ) or a sequence with at least 90% sequence identity thereto, and said bacteriocin has antibacterial activity, and said bacteria is E. faecium, E. faecalis and/or S. hemolyticus; and optionally said bacteria is subjected to heating at between 40 and 50°C before, during and/or after administering or applying said bacteriocin, wherein said bacteriocin comprises at least the consensus sequence KXXXGXXPWE, wherein X may be any amino acid, wherein preferably said bacteriocin is provided in a host cell which produces said bacteriocin. i) said bacteriocin is a peptide of less than 40 amino acids comprising an amino acid sequence selected from: MKFKFNPTGTIVKKLTQYEIAWFKNKHGYYPWEIPRC (SEQ ID NO:1 - EntK1) or a sequence with at least 90% sequence identity thereto, and said bacteriocin has antibacterial activity, and said bacteria is vancomycin-resistant E. faecium; MKFKFNPTGTIVKKLTQYEIAWFKNKHGYYPWEIPRC (SEQ ID NO:1 - EntK1) or a sequence with at least 90% sequence identity thereto, and said bacteriocin has antibacterial activity, and said bacteria is vancomycin-resistant E. faecium; ii) said bacteriocin is a truncated peptide of MLAKIKAMIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA (SEQ ID NO:2 - EntEJ97), consisting of the sequence: KAMIKKFPN PYTLAAKLTTYEI NWYKQQYGRYPWERPVA, AMIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, MIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, IKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, or KKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, or a sequence with at least 90% sequence identity to any of those sequences, and said bacteriocin has antibacterial activity, preferably MIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA (SEQ ID NO:3-EntEJ97short) or a sequence with at least 90% sequence identity thereto, and said bacteria is S. pseudointermedius and/or S. hemolyticus; and MLAKIKAMIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA (SEQ ID NO:2 - EntEJ97), consisting of the sequence: KAMIKKFPN PYTLAAKLTTYEI NWYKQQYGRYPWERPVA, AMIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, MIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, IKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, or KKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, or a sequence with at least 90% sequence identity to any of those sequences, and said bacteriocin has antibacterial activity, KAMIKKFPN PYTLAAKLTTYEI NWYKQQYGRYPWERPVA, AMIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, MIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, IKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, or KKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA, or a sequence with at least 90% sequence identity to any of those sequences, and said bacteriocin has antibacterial activity, preferably MIKKFPNPYTLAAKLTTYEINWYKQQYGRYPWERPVA (SEQ ID NO:3-EntEJ97short) or a sequence with at least 90% sequence identity thereto, and said bacteria is S. pseudointermedius and/or S. hemolyticus; and iii) said bacteriocin is a peptide of less than 40 amino acids comprising an amino acid sequence selected from: MKFKFNPTGTIVKKLTQYEINWYKQQYGRYPWERPVA (SEQ ID NO:4 - K1-EJ) or a sequence with at least 90% sequence identity thereto, and said bacteriocin has antibacterial activity, and said bacteria is E. faecium, E. faecalis and/or S. hemolyticus; and optionally said bacteria is subjected to heating at between 40 and 50°C before, during and/or after administering or applying said bacteriocin, wherein said bacteriocin comprises at least the consensus sequence KXXXGXXPWE, wherein X may be any amino acid, wherein preferably said bacteriocin is provided in a host cell which produces said bacteriocin. MKFKFNPTGTIVKKLTQYEINWYKQQYGRYPWERPVA (SEQ ID NO:4 - K1-EJ) or a sequence with at least 90% sequence identity thereto, and said bacteriocin has antibacterial activity, and said bacteria is E. faecium, E. faecalis and/or S. hemolyticus; and optionally said bacteria is subjected to heating at between 40 and 50°C before, during and/or after administering or applying said bacteriocin, wherein said bacteriocin comprises at least the consensus sequence KXXXGXXPWE, wherein X may be any amino acid, wherein preferably said bacteriocin is provided in a host cell which produces said bacteriocin.