Degradation of antibiotic resistance genes and mobile gene elements in dairy manure anerobic digestion

Abstract

Antibiotic resistance genes (ARGs) are emerging contaminants causing serious global health concern. Interventions to address this concern include improving our understanding of methods for treating waste material of human and animal origin that are known to harbor ARGs. Anaerobic digestion is a commonly used process for treating dairy manure, and although effective in reducing ARGs, its mechanism of action is not clear. In this study, we used three ARGs to conducted a longitudinal bench scale anaerobic digestion experiment with various temperatures (28, 36, 44, and 52°C) in triplicate using fresh dairy manure for 30 days to evaluate the reduction of gene abundance. Three ARGs and two mobile genetic elements (MGEs) were studied: sulfonamide resistance gene (sulII), tetracycline resistance genes (tetW), macrolide-lincosamide-streptogramin B (MLSB) superfamily resistance genes (ermF), class 1 integrase gene (intI1), and transposase gene (tnpA). Genes were quantified by real-time quantitative PCR. Results show that the thermophilic anaerobic digestion (52°C) significantly reduced (p < 0.05) the absolute abundance of sulII (95%), intI1 (95%), tnpA (77%) and 16S rRNA gene (76%) after 30 days of digestion. A modified Collins–Selleck model was used to fit the decay curve, and results suggest that the gene reduction during the startup phase of anaerobic digestion (first 5 days) was faster than the later stage, and reductions in the first five days were more than 50% for most genes.

Fate and seasonality of antimicrobial resistance genes during full‐scale anaerobic digestion of cattle manure across seven livestock production facilities

“…In contrast to Wallace et al.’s (2018) full‐scale study, the consistency of our results with respect to those of previous laboratory‐scale and pilot‐scale studies varies by gene. Our results for tet (W) and sul1 (i.e., no change) generally agree with prior laboratory‐scale studies (Schueler et al., 2021; Sun et al., 2016; Wang et al., 2021), which have found either no change or small changes for these genes. On the other hand, our results for erm (B) and intI1 conflict with previous laboratory and pilot‐scale studies.…”

“…Across gene targets, variation was on the order of 1,000‐fold at median concentrations, and the general order of concentrations from highest to lowest was tet (W) > sul1 ∼ erm (B) > intI1 > tet (A) (Table 2; Figure 1). Concentrations of all targets were generally consistent with those measured in dairy manure by prior studies (He et al., 2020; Munir & Xagoraraki, 2011; Resende et al., 2014; Sandberg & LaPara, 2016; Schueler et al., 2021; Sun et al., 2016; Thames et al., 2012; Wang et al., 2021), indicating consistency in analytical methods among our laboratory and others. Furthermore, the consistency of our tet (A), tet (W), erm (B), and sul1 concentrations with those reported by He et al.…”

“…Few previous studies have quantified the fate of ARGs and/or intI1 in dairy manure during anaerobic digestion, and to the authors' knowledge, only one has done so for a full-scale digestion facility (Wallace et al, 2018). Thus, this study provides a significant body of novel field data that supplements and informs existing studies, particularly those conducted at laboratory scale (Schueler et al, 2021;Sun et al, 2016;Wang et al, 2021) and pilot scale (Resende et al, 2014). Overall, our results are most consistent with Wallace et al's (2018) fullscale study, which quantified the fate of four ARGs [tet(O), tet(W), sul1, and sul2] in a single full-scale anaerobic digester treating dairy manure and found that concentrations of the tetracycline resistance genes did not change, whereas concentrations of the sulfonamide resistance genes underwent relatively small decreases (<0.1 log 10 unit).…”

Clarification of the Dynamic Autothermal Thermophilic Aerobic Digestion Process Using Metagenomic Analysis

“…Changes in the categories of aromatic and secondary metabolism have been reported in methane fermentation ( 29 ) and activated sludge ( 31 ). High temperatures affect prophage induction in Escherichia coli ( 32 ), and mobile genetic elements in daily manure are degraded by thermophilic anaerobic digestion ( 33 ). Decreases in the abundances of phage-related genes in the ATAD process would reflect prophage induction and bacteriolysis in host cells by phages or prophages and degradation of those gene-encoded factors under thermophilic conditions.…”

The Formation of Antibiotic Resistance Genes in Bacterial Communities During Garlic Powder Processing

“…With the further progress of processing, the abundance of ARGs showed different degrees of reduction during the process from GS to GP. Although the processing of GS has undergone heat treatment, the processing temperature and time at this time are not enough to eliminate ARGs ( 42 , 43 ). Although the bacterial communities between GS and GP were very similar, it was not completely consistent, and their association with ARGs was significantly different, which may lead to the different abundance of Arg in GS and GP ( 44 ).…”