engleski

Bloom of resident antibiotic resistant bacteria in soil following manure fertilization

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, we cultured bacteria from soil before and at ten 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 an enrichment of resident soil bacteria that harbor β-lactamases. qPCR indicated that manure treatment enriched the bla (CEP-04) gene, which was 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 is independent of antibiotic exposure of the cows from which the manure was derived. Our data demonstrate the importance of non-intuitive impacts of agricultural practices on the intrinsic resistance of soil microbial communities.

antibiotic resistance; dairy cow manure; ß-lactam antibiotics; microbial communities; resistome

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