Abstract

Provided is a polypeptide having SEQ ID NO. 1, called microcin O (hereafter MccO), and an antibacterial composition comprising the polypeptide, optionally a second antibacterial agent, and a vehicle. The composition is used to inhibit the growth and proliferation of bacteria and to prepare a drug that is useful in the treatment of conditions and/or diseases caused by bacteria. In particular, the composition is used in the preparation of a drug useful in the treatment of conditions and/or diseases caused by both gram positive and gram negative bacteria, which are selected from the group consisting of Staphylococcus aureus, Staphylococcus saprophyticus, Listeria monocytogenes, Escherichia coli O157:H7, Citrobacter freundii and Shigella sonnei.