Microcalorimetric investigation on antibacterial activity of the peptide from Plutella xylostellaA promising antimicrobial agent

The antibacterial activities 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–time curves of MRSA and E. coli growth in the presence of pxCECA1 were recorded using the 3114/3115 Thermal Activity Monitor Air Isothermal Calorimeter based on ampoule mode at 37 °C. Some parameters including 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 to elucidate the antibacterial activity of pxCECA1. The results showed that k, Pmax, and Qt decreased, but I and tg increased or delayed with the increase in pxCECA1 concentration. The IC50 of pxCECA1 on E. coli was 6.122 μg mL−1 and MRSA was 7.809 μg mL−1. It could be concluded 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 antibacterial activity of pxCECA1. The results revealed that pxCECA1 with broad spectrum antimicrobial activities hopefully represented a class of promising substitute of antimicrobial agents.