Multi-drug resistant superbugs are a persistent problem in modern health care. This invention provides an antimicrobial endolysin-Lysostaphin triple fusion protein, comprising (1) an endolysin CHAP endopeptidase domain, (2) an endolysin amidase domain, and (3) a Lysostaphin glycyl-glycine endopeptidase domain. The domains are derived from two proteins that show antimicrobial synergy when used in combination. The protein has specificity and exolytic activity for the peptidoglycan cell wall of untreated, live Staphylococcus aureus from many growth phases i.e. stationary, logarithmic and biofilm growth. The recombinant triple fusion protein comprising the three functional antimicrobial domains is designed to be refractory to resistance development.