摘要
      抗生素耐药性基因是一种新型污染物，对公众健康构成重大威胁。然而，作为反刍动物主要饲料的苜蓿青贮饲料中ARGs的分布和传播风险尚未得到研究。本研究首次通过宏基因组学揭示了植物乳杆菌MTD/1或布氏乳杆菌40788接种对苜蓿青贮饲料中ARGs分布和传播机制的影响。结果表明，多药和杆菌肽抗性基因是青贮苜蓿中的显性ARGs。自然青贮过程增加了30%DM苜蓿青贮饲料中杆菌肽、β-内酰胺和氨基糖苷的丰度，增加了40%DM苜蓿青贮中万古霉素的丰度。同时，长期枯萎增加了新鲜苜蓿中ARG的富集。有趣的是，接种植物乳杆菌MTD/1或布氏乳杆菌40788的苜蓿青贮饲料通过减少宿主细菌和富集质粒中的ARG，降低了总ARG和多药、MLS、万古霉素、氨基糖苷类、四环素和磷霉素抗性基因的丰度。苜蓿青贮饲料中ARG的宿主主要来源于有害细菌或病原体，一些临床ARG是在苜蓿青贮中观察到的。基本上，微生物、MGE和发酵质量的综合作用是ARG在青贮微生态系统中转移和传播的主要驱动力，其中微生物似乎是关键因素。总之，接种本发明的乳酸菌可以降低青贮苜蓿中ARG的丰度，并且在植物乳杆菌处理的青贮饲料中观察到比在布氏乳杆菌处理青贮饲料中更好的效果。
Abstract
Antibiotic resistance genes (ARGs) are a new type of pollutant and pose major threats to public health. However, the distribution and transmission risk of ARGs in alfalfa silage as the main forage for ruminants have not been studied. This study first deciphered the effects of Lactobacillus plantarum MTD/1 or Lactobacillus buchneri 40788 inoculations on distribution and transmission mechanism of ARGs in alfalfa silage by metagenomics. Results showed that multidrug and bacitracin resistance genes were the dominant ARGs in ensiled alfalfa. The natural ensiling process increased the abundances of bacitracin, beta_lactam, and aminoglycoside in alfalfa silage with 30% DM, and vancomycin in alfalfa silage with 40% DM. Meanwhile, prolonged wilting increased ARG enrichment in fresh alfalfa. Interestingly, alfalfa silage inoculated with L. plantarum MTD/1 or L. buchneri 40788 reduced the abundances of total ARG, and multidrug, MLS, vancomycin, aminoglycoside, tetracycline, and fosmidomycin resistance genes by reductions of the host bacteria and the enrichment of ARGs located in the plasmid. The hosts of ARG in alfalfa silage were mainly derived from harmful bacteria or pathogens, and some of the clinical ARGs were observed in alfalfa silage. Basically, the combined effect of microbes, MGEs, and fermentation quality was the major driver of ARG transfer and dissemination in microecosystem of ensiling, where the microbes appeared to be the crucial factor. In summary, inoculation with the present lactic acid bacteria could reduce ARG abundance in ensiled alfalfa, and a better effect was observed in L. plantarum-treated silage than in L. buchneri treated silage.

https://www.sciencedirect.com/science/article/abs/pii/S0304389422021239