Distribution of antibiotic resistant bacteria in different soil types following manure application

Abstract

Abstract Swine manure, commonly applied as organic composts in agricultural fields, is often considered as an important reservoir of antibiotic-resistant bacteria (ARB). We hypothesized that differences in soil types would affect the fate of ARB following manure application. Thus, the distribution of ARB after manure application was further investigated using black, fluvo-aquic and red soils. The results showed that the abundance and diversity of chlortetracycline (CTC)-resistant bacteria (CRB) was fluvo-aquic>red>black soils in control treatment. Additionally, it was affected by manure in black soil, and CTC-manure in both fluvo-aquic and red soils. For the CTC-manure treatment, a higher shift in the number of operational taxonomic units and the community composition of CRB was observed in fluvo-aquic soil than in black and red soils. Thus, it induced resistance development or an increase in soil indigenous microorganisms (Streptomyces, Pseudomonas, Bacillus, Rhodococcus, Enterobacter), which was most evident in fluvo-aquic soil. Furthermore, LEfSe analysis specified the key different bacterial genera that changed significantly between treatments. They were Microbacteriaceaein black soil, Lactobacillus, unclassified_c__Bacilli and Paenibacillus in fluvo-aquic soil, and Dyella, Ralstonia and Bacillusin red soil. Moreover, great and negative influence of soil electric conductivity, total phosphorus and organic matter was observed on Ralstoniaand Bacillus. Streptomyces were significantly positively correlated with pH and organic matter. Overall, CTC-manure would pose a greater influence on soil’s CRB. Therefore, taking measures to control antibiotic residues in manure and to conduct proper return methods according to soil types are important ways to reduce the risk of soil resistant bacteria.