Accumulation of Sulfonamide Resistance Genes in Arable Soils Due to Repeated Application of Manure Containing Sulfadiazine ▿

Two soils were amended three times with pig manure. The abundance of sulfonamide resistance genes was determined by quantitative PCR 2 months after each application. In both soils treated with sulfadiazine-containing manure, the numbers of copies of sul1 and sul2 significantly increased compared to numbers after treatments with antibiotic-free manure or a control and accumulated with repeated applications