Alternative antimicrobials require a deep understanding of their action mechanisms by in vitro assays which support science-based field use. This study focuses on the characterization of bactericidal mechanisms of potential antimicrobial compounds, two organic acids and three single essential oil (EO) compounds against swine enteropathogenic bacteria Escherichia coli, Salmonella enterica subsp. enterica serovar Typhimurium, and Clostridium perfringens. Target concentrations of the compounds were evaluated using the inhibitory potential of the vapor phase and bacterial viability after short-term exposure, while cell targets were disclosed using flow cytometry (FC), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). All tested compounds exhibited vapor phase activity against the three bacterial species, except sodium salt of coconut fatty acid distillates against C. perfringens. Survival test results evidenced that effects on bacterial viability were concentration dependent and higher in single EO compounds than in organic acids. In detail, thymol and its isomer carvacrol were the most effective compounds. Further characterization of thymol and cinnamaldehyde activity revealed that thymol main target was the cell membrane, since it caused striking damages in the membrane permeability, integrity and composition evidenced by FC and FTIR in the three enteric pathogens. In contrast, cinnamaldehyde was more effective against enterobacteria than against C. perfringens and only caused slightly damages at the highest concentration tested. Its target at the molecular level differed between enterobacteria and C. perfringens isolates. The SEM micrographs allowed us to confirm the results previously obtained for both EO compounds by other techniques. Altogether, the study showed the straight effect of these antimicrobials, which could constitute relevant information to optimize their feed inclusion rates in field studies or field use.

替代性抗菌药物需要通过以下方式深入了解其作用机理： 体外支持基于科学的现场使用的分析方法。这项研究的重点是表征潜在的抗菌化合物，两种有机酸和三种单一精油（EO）化合物对猪肠道致病菌的杀菌机理大肠杆菌，肠炎沙门氏菌 亚种 小肠 鼠伤寒血清 产气荚膜梭菌。化合物的目标浓度通过短期暴露后的气相抑制潜力和细菌生存力进行评估，而细胞目标则通过流式细胞术（FC），傅立叶变换红外（FTIR）光谱和扫描电子显微镜（ SEM）。除椰子脂肪酸馏出物的钠盐对三种细菌外，所有测试的化合物均对三种细菌均具有气相活性。产气荚膜梭菌。生存测试结果表明，单一EO化合物对细菌生存力的影响与浓度有关，且高于有机酸。详细地讲，百里酚及其异构体香芹酚是最有效的化合物。百里酚和肉桂醛活性的进一步表征表明，百里酚的主要靶点是细胞膜，因为它引起了三种肠道病原体的膜渗透性，完整性和组成的显着破坏，FC和FTIR证明了这一点。相比之下，肉桂醛对肠细菌的抵抗力要强于对肠杆菌的抵抗力产气荚膜梭菌在测试的最高浓度下只会造成轻微的损坏。肠杆菌和肠杆菌在分子水平上的靶点有所不同产气荚膜梭菌隔离株。SEM显微照片使我们能够确认先前通过其他技术获得的两种EO化合物的结果。总之，该研究表明了这些抗菌剂的直接作用，可以构成相关信息，以在田间研究或田间使用中优化其饲料包入率。