A synergistic antimicrobial composition for inhibiting biofilm formation includes an iron-sequestering glycoprotein, a cationic polypeptide and a chelating agent, or an iron-sequestering glycoprotein and a chelating agent, or an iron-sequestering glycoprotein and a cationic polypeptide. Additionally, surfactants and quaternary ammonium compounds may also be advantageously combined with iron-sequestering glycoproteins in an antimicrobial composition. Methods of using a synergistic composition for inhibiting medical device biofilm formation are also disclosed.