Abstract: In order to investigate the effect of antimicrobial peptide Temprine-La（FS）on the biofilm formation of methicillin-resistant Staphylococcus pseudintermedius（MRSP）, we used Temprine-La as the motif to modify amino acids and synthesize new antimicrobial peptides（T-La（S）, T-La（FS）, RGD-T-La（S）, RGD-T-La（FS）to improve the antibacterial activity. The minimal inhibitory concentration（MBIC）of peptides on MRSP biofilm was determined by microdilution method; The ability of peptides to form MRSP biofilm was detected by crystal violet staining（CV）; The metabolic activity of MRSP biofilm was detected by XTT method; The content of extracellular polysaccharide in MRSP biofilm was detected by polypeptides; the effect of polypeptides on the formation of MRSP biofilm was detected by scanning electron microscopy（SEM）; Q-PCR was used to analyze the effect of polypeptides on the transcription level of MRSP biofilm related genes. The results showed that the MBIC of T-La（S）, RGD-T-La（S）, T-La（FS）and RGD-T-La（FS）to MRSP were 31.3, 15.6, 7.8 and 15.6 μg/mL, respectively; Crystal violet staining（CV）showed that T-La（S）, RGD-T-La（S）, T-La（FS）and RGD-T-La（FS）inhibited the formation of MRSP biofilm; The results of scanning electron microscopy（SEM）showed that polypeptides significantly reduced the extracellular matrix of MRSP biofilm and exposed the bacteria on the surface of the object; Polypeptides could significantly reduce the metabolic activity of MRSP biofilm and inhibit the adhesion of the biofilm; Polypeptides could effectively inhibit the synthesis of extracellular polysaccharides from MRSP biofilm; The results of fluorescent quantitative PCR showed that polypeptides could reduce the transformation of genes related to MRSP biofilm Recording level. Therefore, polypeptides mainly inhibit the formation of MRSP biofilm by affecting the transcription level of biofilm related genes and blocking the synthesis and secretion of extracellular polysaccharides.

Key words: antimicrobial peptide Temprine-La（FS）, methicillin resistant Staphylococcus pseudintermedius （MRSP）, biofilm, related genes