Removal of intl1 and associated antibiotics resistant genes in water, sewage sludge and livestock manure treatments

Antibiotics resistant genes (ARGs) are frequently detected in different media, such as wastewater, sewage sludge, and livestock manure. ARGs have been evidenced to have more and more threats to our environment because of their increase in species and total abundances causing more attention especially in horizontal gene transfer (HGT). The integron, an important form of mobile gene elements transfer ARGs through HGT, is demonstrated to have a high risk to human beings, and the class 1 integron (intl1), a predominant integron, is a marker of the process of horizontal gene transfer. Tetracycline, sulfonamides, macrolide, beta-lactam, trimethoprim, and quinolone plasmid-mediated resistance genes, which are frequently detected in various media and different treatment processes, have been reported to have significant correlations with intl1. Considering the risk of ARGs, especially those associated with intl1, the removal of intl1 and associated ARGs from water, sludge and livestock manure has attracted much more attention recently. Therefore, the mechanism and removal of intl1 and associated ARGs in water depth treatment, sludge and livestock manure digestion and composting process are reviewed in this paper. Besides, the limitation of the current study in this field is discussed, and the key points in the future investigation are provided.