Gómez-García Manuel, Argüello Héctor, Puente Héctor, Mencía-Ares Óscar, González Sandra, Miranda Rubén, Rubio Pedro, Carvajal Ana
Department of Animal Health, Faculty of Veterinary Medicine, Universidad de León, León, Spain.
Front Vet Sci. 2020 Nov 10;7:572947. doi: 10.3389/fvets.2020.572947. eCollection 2020.
Alternative antimicrobials require a deep understanding of their action mechanisms by 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 subsp. serovar Typhimurium, and . 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 . 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 and only caused slightly damages at the highest concentration tested. Its target at the molecular level differed between enterobacteria and 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.
替代性抗菌剂需要通过支持基于科学的现场使用的检测方法来深入了解其作用机制。本研究聚焦于两种有机酸和三种单一精油（EO）化合物等潜在抗菌化合物对猪肠道致病菌亚种鼠伤寒血清型沙门氏菌和其他菌的杀菌机制的表征。利用气相抑制潜力和短期暴露后的细菌活力来评估化合物的目标浓度，同时使用流式细胞术（FC）、傅里叶变换红外（FTIR）光谱和扫描电子显微镜（SEM）来揭示细胞靶点。除了椰子脂肪酸馏出物的钠盐对其他菌无作用外，所有测试化合物对这三种细菌均表现出气相活性。存活测试结果证明，对细菌活力的影响具有浓度依赖性，单一EO化合物的影响高于有机酸。详细而言，百里香酚及其异构体香芹酚是最有效的化合物。对百里香酚和肉桂醛活性的进一步表征表明，百里香酚的主要靶点是细胞膜，因为它在三种肠道病原体中导致了细胞膜通透性、完整性和组成方面的显著损伤，这由FC和FTIR证明。相比之下，肉桂醛对肠道杆菌比对其他菌更有效，并且仅在测试的最高浓度下造成轻微损伤。其在分子水平上的靶点在肠道杆菌和其他菌分离株之间有所不同。SEM显微照片使我们能够通过其他技术确认先前针对这两种EO化合物获得的结果。总之，该研究显示了这些抗菌剂的直接作用，这可为在现场研究或现场使用中优化其饲料添加率提供相关信息。
