Soil antibiotic resistance genes accumulate at different rates over four decades of manure application

Manure can be a source of antibiotic resistance genes (ARGs) that enter the soil. However, previous studies assessing ARG persistence in soil have generally lacked continuity over sampling times, consistency of location, and assessing the impact of discontinuing manure application. We evaluated both short- and long-term ARG accumulation dynamics in soil with a 40-year known history of manure use. Manure application caused a greater abundance of tetracycline, macrolide, and sulfonamide ARGs in the soil. There was an initial spike in ARG abundance resulting from manure bacteria harboring ARGs being introduced to soil, followed by resident soil bacteria out-competing them, which led to ARG dissipation within a year. However, over four decades, annual manure application caused linear or exponential ARG accumulation, and bacteria associated with ARGs differed compared to those in the short term. Eleven years after discontinuing manure application, most soil ARG levels

Automated summary

Manure can introduce antibiotic resistance genes (ARGs) into the soil, leading to their accumulation. Short-term application of manure results in an initial spike in ARG abundance, followed by dissipation within a year. However, long-term application leads to linear or exponential accumulation of ARGs in the soil, and the bacteria associated with ARGs differ compared to the short term. After discontinuing manure application for eleven years, most soil ARG levels decrease.