Characteristics of antibiotic resistance genes in municipal solid waste landfill

Antibiotic resistance genes (ARGs) are known to be emerging environmental contaminants and pose a threat to public health. Solid waste and leachate were collected from the Shanghai Laogang landflls to study the pollution characteristics of the ARGs. The Real-time Quantitative PCR method was used to measure the abundance of six types of target genes, including the sulfonamide antibiotic resistance genes (sul1, sul2), tetracycline resistance genes (tetM, tetQ), aminoglycoside resistance genes (strB, aadA1), macrolide antibiotic resistance genes (ermB, mefA), multiplex resistance gene (mexF), and class I integron gene (intl1). The obtained results showed that the six types of target genes were present in both solid waste and leachate. The concentration of the target genes in solid waste and leachate ranged from 10²-10⁶/ng and 10³-10⁷/ng, respectively. Moreover, the concentration of the multi-resistance genes, aminoglycosides, and sulfonamide antibiotic resistance genes was higher than that of the other genes. The concentration of some target genes in solid waste collected at a depth of 1.5 m was higher than that collected at a depth of 0.5 m, and the total quantity of target genes in the mature leachate was higher than that in the fresh leachate. Additionally, the contribution of some target genes was higher in autumn than in spring. The results demonstrate that the municipal solid waste landfill is a potential reservoir of ARGs and the concentration of target genes demonstrate a spatiotemporal variation.