摘要

抗生素耐药菌的日益泛滥是全球性的公共卫生威胁。农业上抗生素的使用促使抗生素耐药性的传播，但许多农业实践影响耐药性的机制尚不清楚。虽然奶牛养殖场的粪便是作物生产中常见的土壤改良剂，但其对土壤微生物和抗性的影响尚不清楚。为了深入了解这种影响，我们在施用未接受抗生素处理的牛粪之前和之后10个时间点培养来自土壤中细菌。用肥处理的土壤β-内酰胺抗性细菌浓度比用无机肥处理的土壤浓度更高。功能性宏基因组学在处理和未处理的土壤中鉴定了β-内酰胺酶抗性基因，表明粪便改良土壤中抗性细菌的含量较高是由于含有β-内酰胺酶的驻留土壤细菌的富集所致。定量PCR表明，粪便处理使blaCEP - 04基因富集，与以前在假单胞菌中发现的基因高度相似( 96 %)。16SrRNA基因分析表明，假单胞菌属的浓度较高。在粪便改良土壤中增加。通常含有β-内酰胺酶的其他土壤细菌群，包括Janthinobacteriumsp和肺嗜冷菌，也随着粪便处理而增加。这些结果表明，肥料改良导致了土壤中某些抗生素抗性细菌的增加，而这种细菌与来源于牛粪的抗生素无关。我们的数据说明了农业做法可能造成的意外后果，并证明对农业生态系统进行实证分析的必要性。

The increasing prevalence of antibiotic-resistant bacteria is a global threat to public health. Agricultural use of antibiotics is believed to contribute to the spread of antibiotic resistance, but the mechanisms by which many agricultural practices influence resistance remain obscure. Although manure from dairy farms is a common soil amendment in crop production, its impact on the soil microbiome and resistome is not known. To gain insight into this impact, we cultured bacteria from soil before and at 10 time points after application of manure from cows that had not received antibiotic treatment. Soil treated with manure contained a higher abundance of β-lactam–resistant bacteria than soil treated with inorganic fertilizer. Functional metagenomics identified β-lactam–resistance genes in treated and untreated soil, and indicated that the higher frequency of resistant bacteria in manure-amended soil was attributable to enrichment of resident soil bacteria that harbor β-lactamases. Quantitative PCR indicated that manure treatment enriched the blaCEP-04 gene, which is highly similar (96%) to a gene found previously in a Pseudomonas sp. Analysis of 16S rRNA genes indicated that the abundance of Pseudomonas spp. increased in manure-amended soil. Populations of other soil bacteria that commonly harbor β-lactamases, including Janthinobacterium sp. and Psychrobacter pulmonis, also increased in response to manure treatment. These results indicate that manure amendment induced a bloom of certain antibiotic-resistant bacteria in soil that was independent of antibiotic exposure of the cows from which the manure was derived. Our data illustrate the unintended consequences that can result from agricultural practices, and demonstrate the need for empirical analysis of the agroecosystem.

http://www.pnas.org/content/111/42/15202.short