The aim of this study is to investigate the inhibitory effects and mechanism of three or-ganic acids,including formic acid(FA),butyric acid(BA)and lactic acid(LA),on the pathogenic-ity of Salmonella enteritidis(SE),Escherichia coli(EC)and Staphylococcus aureus(SA).The growth of pathogens was detected by Minimum Inhibitory Concentration(MIC)and Oxford Cup antimicrobial zone assays.The motility of pathogens was detected by soft agar plate method,and the biofilm of pathogens was detected by crystal violet staining.Quantitative real-time polymerase chain reaction(qRT-PCR)was used to measure the expression levels of genes related to the patho-genicity of SE.The results showed that FA and BA significantly inhibited the growth of SE,EC and SA,and FA had a superior inhibitory effect on EC(MIC:0.25 g/L;inhibition zone:20.0 mm)and SA(MIC:0.5 g/L;inhibition zone:25.0 mm).In addition,the three organic acids significantly inhibited the motility of SE,EC and SA as accessed by swimming and swarming assays,and FA showed the best inhibition effect.Besides,the three organic acids,especially FA,markedly inhibited the biofilm formation of SE,EC and SA.Finally,our results showed that the three organic acids in-hibited the expression of the main virulence genes encoded by SPI-1(InvA,InvF,SopE,SopB,SipB,HilA and SipA),SPI-2(SopD2),pili-related genes(FliF,LpfA,SefA and FimF)and flagellum-related genes(FlhD,FliC and FliD)of SE.This study demonstrates that FA,BA,and LA significantly inhibited the growth and pathogenicity of the four pathogens,among which FA showed the most obvious effect on inhibiting the growth,motility,biofilm formation and virulence gene expression.Our study provided a theoretical basis for the application of organic acids in the field of animal husbandry.

The aim of this study is to investigate the inhibitory effects and mechanism of three or-ganic acids,including formic acid(FA),butyric acid(BA)and lactic acid(LA),on the pathogenic-ity of Salmonella enteritidis(SE),Escherichia coli(EC)and Staphylococcus aureus(SA).The growth of pathogens was detected by Minimum Inhibitory Concentration(MIC)and Oxford Cup antimicrobial zone assays.The motility of pathogens was detected by soft agar plate method,and the biofilm of pathogens was detected by crystal violet staining.Quantitative real-time polymerase chain reaction(qRT-PCR)was used to measure the expression levels of genes related to the patho-genicity of SE.The results showed that FA and BA significantly inhibited the growth of SE,EC and SA,and FA had a superior inhibitory effect on EC(MIC:0.25 g/L;inhibition zone:20.0 mm)and SA(MIC:0.5 g/L;inhibition zone:25.0 mm).In addition,the three organic acids significantly inhibited the motility of SE,EC and SA as accessed by swimming and swarming assays,and FA showed the best inhibition effect.Besides,the three organic acids,especially FA,markedly inhibited the biofilm formation of SE,EC and SA.Finally,our results showed that the three organic acids in-hibited the expression of the main virulence genes encoded by SPI-1(InvA,InvF,SopE,SopB,SipB,HilA and SipA),SPI-2(SopD2),pili-related genes(FliF,LpfA,SefA and FimF)and flagellum-related genes(FlhD,FliC and FliD)of SE.This study demonstrates that FA,BA,and LA significantly inhibited the growth and pathogenicity of the four pathogens,among which FA showed the most obvious effect on inhibiting the growth,motility,biofilm formation and virulence gene expression.Our study provided a theoretical basis for the application of organic acids in the field of animal husbandry.