The present invention relates to polypeptides comprising an amino sequence selected from the group consisting of: SEQ ID NO: 1, and fragments and derivatives of these. The invention also relates to the corresponding nucleic acids vectors, host cells and compositions. The present inventions also relates to the use of said polypeptides, nucleic acids, vectors, host cells and compositions in a method for treatment of the human or animal body by surgery or therapy or in diagnostic methods practiced on the human or animal body, in particular for the treatment or prevention of Gram-negative bacterial infections. The polypeptides, nucleic acids, vectors, host cells and compositions according to the invention may also be used as an antimicrobial in food or feed, or in cosmetics, as disinfecting agent or in the environmental field.
