为有效解决细菌耐药性、药物残留和污染问题，2020年我国将在饲料端禁抗，在此背景下，细菌解除了抗生素的经常性选择压力，病原菌的流行株及其耐药性、毒力因子、抗原性、细菌感染谱和发病率等将发生一系列的变化，但仔猪尤其是处于断奶应激期的仔猪其重要细菌感染的生态演替变化规律尚不清楚；将新型生物抗菌制剂——抗菌肽用于细菌感染的防治已有良好的基础，但其对仔猪细菌感染防治的分子机制尚待进一步阐明。因此，急需揭示饲料端禁抗后仔猪主要病原菌感染的生态演化规律，阐明抗菌肽防治仔猪细菌感染的机制。本项目选择吉林省规模化养猪场的仔猪，以大肠杆菌、沙门菌、金黄色葡萄球菌为主要监测对象，通过对仔猪的细菌分子流行病学研究，揭示仔猪主要病原菌的演化规律；基于此，应用自行研制的酵母抗菌肽用于仔猪细菌感染的防治研究，进一步揭示抗菌肽防治仔猪细菌感染的分子机制。本项目将为我国饲料禁抗后仔猪细菌病的防治提供重要的理论与实验支持。

In order to effectively solve the problem of bacterial antibiotic-resistance, antibiotic residues and pollution, in 2020, China will ban antibiotics in the fodder of livestock and poultry farming. Once the banning is implemented, the frequent selection pressure of antibiotics on the bacteria will be relieved. There will be a series of changes in the epidemic strains of pathogens, their antibiotic-resistance, virulence factors, antigenicity, bacterial infection spectrum and morbidity. However, the ecological succession of important bacterial infections in piglets (especially those in weaning stress period) is still unclear when antibiotics are banned in the fodder. Although, there is a good foundation for the prevention and treatment of bacterial infections by using antibacterial peptides, the molecular mechanism of antibacterial peptides preventing and treating bacterial infection in piglets should be further clarified. Therefore, it is urgent to reveal the ecological succession of the main pathogen infection of piglets when banning antibiotics in the fodder, and to elucidate the mechanism of antibacterial peptides in preventing and treating bacterial infection in piglets. For revealing the evolution of the main pathogens of piglets when banning antibiotics in the fodder, the molecular epidemiology of Escherichia coli, Salmonella and Staphylococcus aureus derived from piglets of large-scale pig farms in Jilin Province will be studied. Furthermore, antibacterial peptide expressed by yeast will be used for the prevention and treatment of bacterial infection in piglets, and the molecular mechanism of antibacterial peptides in preventing bacterial infection in piglets will be revealed. This project will provide important theoretical and experimental support for the prevention and treatment of bacterial diseases in piglets after banning antibiotics in the fodder in China.