摘要Background:The effects of perilla leaf oil on the antibacterial activity,biofilm formation,and group sensing related genes of Salmonella dysentery in chickens were investigated.Perilla leaf oil was compared with the antibiotic gentamycin hydrochloride,which is commonly used in the chicken industry,to provide experimental data and theoretical basis for the further development of perilla leaf oil as a new type of antimicrobial drug to replace feed antibiotics.Methods:The minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)of perilla leaf oil and the antibiotic aureomycin hydrochloride against three clinical isolates of Salmonella typhimurium were determined by microbial broth dilution,and SP-2 was screened out from them.The dynamic bactericidal effect of perilla leaf oil and aureomycin hydrochloride on SP-2 was obtained by the viable bacteria counting method and the time-bactericidal curves.The successful establishment of biological periplasm and the corresponding times of its various growth stages of adhesion,aggregation,and maturation were determined by cell counting kit-8(CCK-8)reagent and scanning electron microscopy(SEM).The effects of different concentrations of perilla leaf oil on biofilm at different stages were investigated by CCK-8 method and semi-quantitative adhesion method of crystalline violet,and the changes in microstructure and morphology of biofilm at different stages under the effect of drugs were observed by SEM.The effect of perilla leaf oil on the expression of genes related to the formation of the population sensing system(luxS and sdiA)in the test strain SP-2 was detected by qRT-PCR.Results:The MIC value of perilla leaf oil on SP-2 was 2.000±0.000 mg/mL.Perilla leaf oil and gentamycin hydrochloride could effectively inhibit and kill SP-2 in a planktonic state,and delay the entry of bacteria into the logarithmic growth period.6 h,24 h,and 48 h were chosen as the time points for the drug intervention in the initial adhesion,aggregation,and maturation stages of the biofilm of SP-2.1 mg/mL perilla leaf oil was significantly better than the same concentration of gentamycin hydrochloride in removing the total amount of biofilm of SP-2 at all growth stages(P<0.05).The inhibitory effect of 4 mg/mL perilla leaf oil on the bacterial metabolic activity in SP-2 biofilm at the mature stage was significantly better than that of the same concentration of gentamycin hydrochloride(P<0.01).For SP-2 biofilm at all stages of growth,different concentrations of perilla leaf oil significantly down-regulated the expression of luxS and sdiA genes(P<0.05),interfered with the group sensing system of SP-2,and inhibited the formation of its biofilm.Conclusion:The perilla leaf oil has a good antibacterial activity and biofilm inhibition effect on SP-2 of S.Pullorum at different growth stages.