Surfactin is a potent cyclic lipopeptide biosurfactants consists of four isomers (Surfactin A, B, C and D), which mediates flux of mono-and divalent cations, such as calcium, across lipid bilayer membranes. Surfactin can act as an antimicrobial adjuvant with anti-bacterial, anti-fungal, antimycoplasma and hemolytic effects[2]. Surfactin also has antiviral activity against a variety of enveloped viruses.In Vitro: Surfactin can increase the activity of NSC277174 against avian pathogenic Escherichia coli (APEC) in vitro with antimicrobial assays such as minimum inhibitory concentrations (MIC) and fractional inhibitory concentration (FIC). For APEC O78 strain, the MIC of NSC277174 and Surfactin are 1000 ug/ml and >1mg/ml, respectively.In Vivo: In the model of chick infection (inoculation of E.coli), Surfactin exerts adjuvant effects with NSC277174 against APEC by lowering the numerical value of mortality and liver bacterial loads, and regulating the expression of inflammatory cytokines et al. Surfactin can act as a novel antimicrobial adjuvant with NSC277174 against AEPC infection in chicken.