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The anti-bacterial activity of a kind of novel peptide from Plutella xylostella (pxCECA1),on methicillin resistant staphylococcus aureus (MRSA) and Escherichia coli (E.coli) growth were investigated by microcalorimetry.The heat flow power (HPE)-time curves of MRSA and E.coli growth in the presence of pxCECA1 were measured using the 3114/3115 Thermal Activity Aonitor (TAM) Air Isothermal Calorimeter,ampoule mode,at 37 °C.Some parameters such as growth rate constant k,maximum power output Pmax,total heat Output Qt,generation time tg,growth inhibitory ratio I and half-inhibitory concentration of the drugs IC50,were obtained by analyzing the (HPE)-time curves to elucidate the antibacterial activity of pxCECA1.The results showed that k,Pmax and Qt decreased,but I and tg increased or delayed with increasing concentration of pxCECA1.The IC50 of pxCECA1 on E.coli was 5.766 μg·mL-1 and MRSA was 7.684 μg·mL-1.It could be drawn a conclusion that pxCECA1 had stronger inhibitory effect on E.coli than MRSA.In vivo test was simultaneously performed using an E.coli and MRSA infection model to validate the anti-bacterial activity of pxCECA1.The results revealed that pxCECA1 with broad spectrum antimicrobial activity hopefully represented a kind of promising substitute of antimicrobial agents.