Autoclave treatment of pig manure does not reduce the risk of transmission and transfer of tetracycline resistance genes in soil: successive determinations with soil column experiments. - Related Documents




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813201.0000Autoclave treatment of pig manure does not reduce the risk of transmission and transfer of tetracycline resistance genes in soil: successive determinations with soil column experiments. The increasing use of antibiotics, especially tetracycline, in livestock feed adversely affects animal health and ecological integrity. Therefore, approaches to decrease this risk are urgently needed. High temperatures facilitate antibiotic degradation; whether this reduces transmission risk and transfer of tetracycline-resistant bacteria (TRBs) and tetracycline resistance genes (TRGs) in soil remains unknown. Successive experiments with soil columns evaluated the effects of autoclaving pig manure (APM) on soil TRB populations and TRGs over time at different soil depths. The data showed sharp increases in TRB populations and TRGs in each subsoil layer of PM (non-APM) and APM treatments within 30 days, indicating that TRBs and TRGs transferred rapidly. The level of TRBs in the upper soil layers was approximately 15-fold higher than in subsoils. TRBs were not dependent on PM and APM levels, especially in the late phase. Nevertheless, higher levels of APM led to rapid expansion of TRBs as compared to PM. Moreover, temporal changes in TRB frequencies in total culturable bacteria (TCBs) were similar to TRBs, indicating that the impact of PM or APM on TRBs was more obvious than for TCBs. TRBs were hypothesized to depend on the numbers of TRGs and indigenous recipient bacteria. In the plough layer, five TRGs (tetB, tetG, tetM, tetW, and tetB/P) existed in each treatment within 150 days. Selective pressure of TC may not be a necessary condition for the transfer and persistence of TRGs in soil. High temperatures might reduce TRBs in PM, which had minimal impact on the transmission and transfer of TRGs in soil. Identifying alternatives to decrease TRG transmission remains a major challenge.201626517996
753810.9988Short-term thermophilic treatment cannot remove tetracycline resistance genes in pig manures but exhibits controlling effects on their accumulation and spread in soil. In this work, a microcosm experiment was conducted to merely mimic thermophilic phase in aerobic composting with pig manures in order to explore: (i) the effect of thermophilic phase in composting on the abundances of tetracycline resistance genes (TRGs); and (ii) the impacts of the treated manures on the abundances of TRGs in soil. It was found that 4days of thermophilic process reduced the abundance of TRGs in pig manures by ∼1 lg unit compared to the samples without treatments, suggesting that other phases in composting may play significant roles in removal of TRGs. Once pig manures with thermophilic treatment were applied to soil, TRGs abundances decreased to the levels in unfertilized soil. With correlation analyses, it was concluded that pig manure derived tetracycline-resistant bacteria (TRB) and nutrients exerted different effects on TRGs abundances in soil. In conclusion, short-term thermophilic treatment cannot remove tetracycline resistance genes in pig manures but exhibits controlling effects on their accumulation and spread in soil. Nutrients enrichment in soil following manuring of treated pig manures, together with a large proportion of gram-positive TRB left in treated pig manures with less risk to TRGs spread, contributed to the controlling effects.201728715744
753520.9988The effects of pig manure application on the spread of tetracycline resistance in bulk and cucumber rhizosphere soils: a greenhouse experiment. It is important to understand the dynamics of tetracycline-resistant bacteria (TRB) and tetracycline resistance genes (TRGs) in bulk and rhizosphere soils for evaluating the spread of TRGs from pig manure to human. In this work, a greenhouse experiment was conducted to investigate the difference in abundance of TRB, tetracycline-resistant Escherichia coli (TRE), tetracycline-resistant Pseudomonas spp. (TRP), and TRGs between bulk and cucumber rhizosphere soils. The application of pig manure resulted in the long-term persistence of TRB, TRE, TRP, and TRGs in bulk soil and rhizosphere of cucumber for at least 65 days. Pig manure application dose was the major driving force in altering the abundances of TRB and TRE, whereas TRP was disturbed mainly by compartment (bulk soil or rhizosphere). Both TRE and the percentage of TRE in bulk and rhizosphere soils increased linearly with an increase in dose of pig manure. The exponential relationships between pig manure dose and TRP along with TRP percentage were also noted. There were significant differences in the relative abundances of TRGs between bulk and cucumber rhizosphere soils, suggesting the use of pig manure exerted a more lasting impact on the spread of TRGs in the rhizosphere than in the bulk soil.201728222270
753630.9988The effects of tetracycline concentrations on tetracycline resistance genes and their bacterial hosts in the gut passages of earthworms (Eisenia fetida) feeding on domestic sludge. Vermi-composting is considered to be a feasible method for reducing tetracycline resistance genes (TRGs) in the sludge. Nevertheless, the way different gut passages of earthworm might affect the fates of TRGs and whether this process is affected by tetracycline (TC) concentrations need to be further investigated. In this study, we examined the effects of TC concentrations on changes in TRGs and bacterial communities in gut passages of earthworm were determined by using quantitative PCR and Illumina high-throughput sequencing. TRGs and intI1 were mainly reduced in the hindgut under the TC concentrations ranging from 0 to 25 mg/kg, while they were enriched under higher TC stress exposure. Consequently, we suggest the TC limitation of 25 mg/kg in the domestic sludge (DS) for vermi-composting. Although the predominant genera were TC sensitive under TC stress, many bacterial hosts harboring multiple TRGs (especially those in the hindgut) should be paid further attention to. In the foregut, five genera with abundant tetracycline-resistant bacteria (TRB) were specialized taxa. Among these genera, Unclassified_Solirubrobacterales and Pirellulaceae were probably related to the digestion processes. Other unclassified taxa related to the TRGs were probably derived from the DS. Five genera with abundant TRB were shared in the gut passages, and three specialized genera in the hindgut. These genera could spread TRGs and intI1 to the environment. These results suggest that vermi-composting is a feasible approach for TRG control in the DS containing TC concentration that does not exceed 25 mg/kg. Fates of TRGs and intI1 widely differ in the gut passages, showing inevitable connections with bacterial communities.201931637618
696140.9986Impacts of supplementing chemical fertilizers with organic fertilizers manufactured using pig manure as a substrate on the spread of tetracycline resistance genes in soil. Using pig manure (PM) compost as a partial substitute for the conventional chemical fertilizers (CFs) is considered an effective approach in sustainable agricultural systems. This study aimed to analyze the impacts of supplementing CF with organic fertilizers (OFs) manufactured using pig manure as a substrate on the spread of tetracycline resistance genes (TRGs) as well as the community structures and diversities of tetracycline-resistant bacteria (TRB) in bulk and cucumber rhizosphere soils. In this study, three organic fertilizers manufactured using the PM as a substrate, namely fresh PM, common OF, and bio-organic fertilizer (BF), were supplemented with a CF. Composted manures combined with a CF did not significantly increase TRB compared with the CF alone, but PM treatment resulted in the long-term survival of TRB in soil. The use of CF+PM also increased the risk of spreading TRGs in soil. As beneficial microorganisms in BF may function as reservoirs for the spread of antibiotic resistance genes, care should be taken when adding them to the OF matrix. The PM treatment significantly altered the community structures and increased the species diversity of TRB, especially in the rhizosphere soil. BF treatment caused insignificant changes in the community structure of TRB compared with CF treatment, yet it reduced the species diversities of TRB in soil. Thus, the partial use of fresh PM as a substitute for CF could increase the risk of spread of TRGs. Apart from plant growth promotion, BF was a promising fertilizer owing to its potential ability to control TRGs.201627152658
753750.9986Swine-manure composts induce the enrichment of antibiotic-resistant bacteria but not antibiotic resistance genes in soils. Composting is a common and effective strategy for reducing antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) from animal manure. However, it is unclear whether the advantages of composting for the control of ARGs and ARB can be further increased in land application. This study investigated the fate of ARB and ARGs after land application of swine-manure composts (SMCs) to three different soil types (red soil, loess and black soil). The results showed that although the SMCs caused an increase in the abundance of total ARGs in the soil in the short period, they significantly reduced (p < 0.01) the abundance of total ARGs after 82 days compared to the control. The decay rate of ARGs reflected by the half-life times (t(1/2)) varied by soil type, with red soil being the longest. The SMCs mainly introduced ermF, tetG and tetX into the soils, while these ARGs quickly declined to the control level. Notably, SMCs increased the number of ARB in the soils, especially for cefotaxime-resistant bacteria. Although SMCs only affected the microbiome significantly during the early stage (p < 0.05), it took a much longer time for the microbiome to recover compared to the control. Statistical analysis indicated that changes in the microbial community contributed more to the fate of ARGs during SMCs land application than other factors. Overall, it is proposed that the advantages of ARGs control in the composting process for swine manure can be further increased in land application, but it can still bring some risks in regard to ARB.202337536132
758060.9985Inactivation of antibiotic resistance genes in antibiotic fermentation residues by ionizing radiation: Exploring the development of recycling economy in antibiotic pharmaceutical factory. Antibiotic fermentation residues are a kind of hazardous waste due to the existence of the residual antibiotics and the potential risk to generate antibiotics resistance genes (ARGs). The appropriate treatment and disposal of antibiotic fermentation residues is imperative. In this study ionizing radiation was applied to treat the antibiotic fermentation residues and the removal efficiencies of antibiotic (erythromycin), ARGs (ermB and ermF) and antibiotic resistant bacteria were investigated. The experimental results showed that erythromycin A content in antibiotic fermentation residues decreased by 86% when the dose was 10 kGy. Moreover, the abundance of ermB and ermF reduced by 89% and 98% at 10 kGy irradiation. Over 99% of total bacteria was removed and antibiotic resistant bacteria (ARB) were less than detection limit after 10 kGy irradiation. Ionizing radiation process is a promising technology for simultaneously removing antibiotic and inactivating ARGs and ARB in antibiotic fermentation residues. Moreover, the irradiation at 10 kGy had no significant influence on the macromolecules organic matters (protein, polysaccharides) of the antibiotic fermentation residues, suggesting that the treated fermentative residues can be used as fertilizer, which could provide the technical support for the development of recycling economy in antibiotic pharmaceutical factory.201930691886
695570.9985Soil antibiotic resistance genes accumulate at different rates over four decades of manure application. Manure can be a source of antibiotic resistance genes (ARGs) that enter the soil. However, previous studies assessing ARG persistence in soil have generally lacked continuity over sampling times, consistency of location, and assessing the impact of discontinuing manure application. We evaluated both short- and long-term ARG accumulation dynamics in soil with a 40-year known history of manure use. Manure application caused a greater abundance of tetracycline, macrolide, and sulfonamide ARGs in the soil. There was an initial spike in ARG abundance resulting from manure bacteria harboring ARGs being introduced to soil, followed by resident soil bacteria out-competing them, which led to ARG dissipation within a year. However, over four decades, annual manure application caused linear or exponential ARG accumulation, and bacteria associated with ARGs differed compared to those in the short term. Eleven years after discontinuing manure application, most soil ARG levels declined but remained elevated. We systematically explored the historical accumulation of ARGs in manured soil, and provide insight into factors that affect their persistence.202336444046
724680.9985Tetracycline resistance genes are more prevalent in wet soils than in dry soils. This study aimed to reveal the effects of water content on the spread of tetracycline resistance genes (TRGs) in the soil. Amendments of four samples with different soil water contents, namely 16% (dry soil) and 25% (wet soil), and with or without pig manures (PM) were conducted under laboratory conditions. Quantitative polymerase chain reaction (q-PCR) results showed that the relative abundance of TRGs (tetB, tetC, tetM, tetO, tetT, and tetZ) in the wet soils was significantly higher than that in the dry soils whether under fertilization or non-fertilization conditions. Moreover, PM application enhanced the relative abundance of TRGs. The absolute copies of TRGs did not decline with the decrease in 16S rRNA genes in wet soils, implying that most TRGs were probably located in facultative anaerobic bacteria. However, cultivable tetracycline-resistant bacteria (TRB) in the wet soils were not in line with the q-PCR results, further indicating that aerobes might not account for the increases in the relative abundance of TRGs. Diversities of aerobic TRB were significantly higher in the wet soils than in the dry soils, especially on days 14 and 28. The patterns of community structures of aerobic TRB in the wet soils or dry soils containing PM were different from those in the dry soils. Together, this study showed that the variations in bacterial communities between the wet and dry soils, especially reflected in the diversity of aerobic TRB and/or community structure of facultative anaerobic TRB, might be an important reason behind the changes in the abundance of TRGs.201829573724
706990.9985Native soil microorganisms hinder the soil enrichment with antibiotic resistance genes following manure applications. Bacterial genes responsible for resistance to antibiotic agents (ARG) are spread from livestock to soil through application of manure, threatening environmental and human health. We investigated the mechanisms of ARG dissemination and persistence to disentangle i) the influence of nutrients and microorganisms on the soil tetracycline (TET) resistome, and ii) the role of indigenous soil microbiota in preventing ARG spread. We analysed short-term (7 days) and persistent (84 days) effects of manure on the resistome of three antibiotic-free pasture soils. Four microcosm treatments were evaluated: control, mineral nutrient fertilization, and deposition of a layer of fresh manure onto soil or γ-irradiated soil. We quantified five TET-resistance genes, isolated 135 TET-resistant bacteria and sequenced both culturable TET-resistant and whole bacterial communities. Manure amendments, but not nutrient addition, increased the abundance of TET-r genes such as tet(Y). Such changes persisted with time, in contrast with the TET-resistant bacterial composition, which partially recovered after manure amendments. Manured γ-irradiated soils showed significantly lower nutrient content and higher TET-r gene abundance than non-irradiated soils, suggesting that native soil bacteria are essential for the fertilization effect of manure on soil as well as control the dissemination of potentially risky TET-r genes.201931043618
6954100.9985Temporal effects of repeated application of biogas slurry on soil antibiotic resistance genes and their potential bacterial hosts. Biogas slurry, a liquid end product of animal manure fermentation, is widely used as fertilizer in crop fields. Land application may introduce antibiotics and related resistance genes from livestock production into agricultural soil. Nevertheless, changes in antimicrobial resistance in soil where biogas slurry has been repeatedly applied are not fully understood. In the present study, 13 veterinary antibiotics were analyzed in soils that were repeatedly sprayed with biogas slurry, and simultaneously, temporal changes in antibiotic resistance genes (ARGs) and bacterial community composition were investigated using a real-time quantitative PCR assay and MiSeq sequencing. Long-term repeated application of biogas slurry did not result in excessive accumulation of antibiotic residuals in the soil but increased the abundance of ARGs and facilitated ARG transfer among potential hosts. Although the quantitative PCR assay showed a decreasing trend for the relative abundance of ARGs over time, a relevance network analysis revealed highly complex bacteria-ARG co-occurrence after long-term application, which implied that repeated application might intensify horizontal gene transfer (HGT) of ARGs among different bacterial hosts in soil. The increased relative abundance of the intl1 gene supported the shift in ARG-bacteria co-occurrence. Furthermore, ordination analysis showed that the distributions of antibiotic resistance bacteria (ARB) and ARGs were closely related to application duration than to the influence of antibiotic residuals in the biogas slurry-treated soil environment. Additionally, natural level of ARG abundance in untreated soils indirectly suggested the presence/absence of antibiotics was not a key determinant causing the spread of antimicrobial resistance. This study provides improved insight into the effects of long-term repeated application of biogas slurry on the shift in ARG abundances and bacteria-ARG co-occurrence in soils, highlighting the need to focus on the influence of changed soil environment on the ARG transfer.202031818620
8076110.9985Effects of chlortetracycline and copper on tetracyclines and copper resistance genes and microbial community during swine manure anaerobic digestion. As antibiotic and heavy metals are over used in the livestock industry, animal manure is a reservoir of antibiotic resistance genes (ARGs). Anaerobic digestion has been reported to have the potential to reduce ARGs. However, few studies investigated whether reduction of ARGs would be affected by different external pressures including antibiotics and heavy metals during anaerobic digestion. The purpose of this study was thus to investigate effects of both chlortetracycline (CTC) and Cu on reduction of ARGs, heavy metal resistance genes (HMRGs) and mobile genetic elements (MGEs) during the swine manure anaerobic digestion. The results showed that the predominant ARGs (tetO, tetW, tetX, tetL) could be effectively reduced (approximately 1.00 log copies/g TS) through mesophilic anaerobic digestion. Microbial community evolution was the main driver. It was interesting that Treponema might indicate the termination of anaerobic digestion and compete with ARGs host bacteria. Addition of CTC, Cu and CTC+Cu affected microbial community change and hindered removal of ARGs, especially, CTC+Cu seriously affected Treponema and ARGs during anaerobic digestion.201728432950
6952120.9985Modeling the vertical transport of antibiotic resistance genes in agricultural soils following manure application. Antibiotic resistance genes (ARGs) may be introduced to agricultural soil through the land application of cattle manure. During a rainfall event, manure-borne ARGs may infiltrate into subsurface soil and leach into groundwater. The objective of this study was to characterize and model the vertical transport of manure-borne ARGs through soil following the land application of beef cattle manure on soil surface. In this study, soil column experiments were conducted to evaluate the influence of manure application on subsurface transport of four ARGs: erm(C), erm(F), tet(O) and tet(Q). An attachment-detachment model with the decay of ARGs in the soil was used to simulate the breakthrough of ARGs in leachates from the control column (without manure) and treatment (with manure) soil columns. Results showed that the first-order attachment coefficient (k(a)) was five to six orders of magnitude higher in the treatment column than in the control column. Conversely, the first-order detachment and decay coefficients (k(d) and μ(s)) were not significantly changed due to manure application. These findings suggest that in areas where manure is land-applied, some manure-borne bacteria-associated ARGs will be attached to the soil, instead of leaching to groundwater in near terms.202134087637
7963130.9985Distribution of tetracycline resistance genes in anaerobic treatment of waste sludge: The role of pH in regulating tetracycline resistant bacteria and horizontal gene transfer. Although pH value has been widely regarded as an important factor that affects resource recovery of waste sludge, the potential influence of diverse pHs on the distribution of tetracycline resistance genes (TRGs) during sludge anaerobic treatment is largely unknown. Here we reported that in the range of pH 4-10, 0.58-1.18 log unit increase of target TRGs was observed at pH 4, compared with that at pH 7, while 0.70-1.31 log unit further removal were obtained at pH 10. Mechanism study revealed that varied pHs not only altered the community structures of tetracycline resistant bacteria (TRB), but also changed their relative abundances, benefitting the propagation (acidic pHs) or attenuation (alkaline pHs) of TRB. Further investigation indicated that the amount and gene-possessing abilities of key genetic vectors for horizontal TRGs transfer were greatly promoted at acidic pHs but restricted under alkaline conditions.201627485281
7072140.9985Stockpiling versus Composting: Effectiveness in Reducing Antibiotic-Resistant Bacteria and Resistance Genes in Beef Cattle Manure. Manure storage methods can affect the concentration and prevalence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in cattle manure prior to land application. The objective of this study was to compare stockpiling and composting with respect to their effectiveness in reducing ARB and ARGs in beef cattle manure in a field-scale study. Field experiments were conducted in different seasons with different bulking agents for composting. For both the winter-spring cycle and the summer-fall cycle, ARB concentrations declined below the limit of quantification rapidly in both composting piles and stockpiles; however, ARB prevalence was significantly greater in the composting piles than in the stockpiles. This was likely due to the introduction of ARB from bulking agents. There was no significant change in ARG concentrations between initial and final concentrations for either manure storage treatment during the winter-spring cycle, but a significant reduction of the ARGs erm(B), tet(O), and tet(Q) over time was observed for both the composting pile and stockpile during the summer-fall cycle. Results from this study suggest that (i) bulking agent may be an important source of ARB and ARGs for composting; (ii) during cold months, the heterogeneity of the temperature profile in composting piles could result in poor ARG reduction; and (iii) during warm months, both stockpiling and composting can be effective in reducing ARG abundance. IMPORTANCE Proper treatment of manure is essential to reduce the spread of antibiotic resistance and protect human health. Stockpiling and composting are two manure storage methods which can reduce antibiotic-resistant bacteria and resistance genes, although few field-scale studies have examined the relative efficiency of each method. This study examined the ability of both methods in both winter-spring and summer-fall cycles, while also accounting for heterogeneity within field-scale manure piles. This study determined that bulking agents used in composting could contribute antibiotic-resistant bacteria and resistance genes. Additionally, seasonal variation could hinder the efficacy of composting in colder months due to heterogeneity in temperature within the pile; however, in warmer months, either method of manure storage could be effective in reducing the spread of antibiotic resistance.202134085860
6928150.9985Assessing the effects of tylosin fermentation dregs as soil amendment on macrolide antibiotic resistance genes and microbial communities: Incubation study. Tylosin fermentation dregs (TFDs) are biosolid waste of antibiotics tylosin production process which contain nutritious components and may be recycled as soil amendments. However, the specific ecological safety of TFDs from the perspective of bacterial resistance in soil microenvironment is not fully explored. In the present study, a series of replicated lab-scale work were performed using the simulated fertilization to gain insight into the potential environmental effects and risks of macrolide antibiotic resistance genes (ARGs) and the soil microbial communities composition via quantitative PCR and 16S rRNA sequencing following the TFDs land application as the soil amendments. The results showed that bio-processes might play an important role in the decomposition of tylosin which degraded above 90% after 20 days in soil. The application of TFDs might induce the development of antibiotic-resistant bacteria, change soil environment and reduce the microbial diversity. Though the abundances of macrolide ARGs exhibited a decreasing trend following the tylosin degradation, other components in TFDs may have a lasting impact on both macrolide ARGs abundance and soil bacterial communities. Thus, this study pointed out the fate of TFDs on soil ecological environment when directly applying into soil, and provide valuable scientific basis for TFDs management.202032648501
7040160.9985The maturity period is the main stage of antibiotic resistance genes reduction in aerobic composting process of swine manure in sub-scale farms. This study was focused on the changes of antibiotic resistance genes (ARGs) and their potential host bacteria during the swine manure composting on sub-scale farms. Eight target ARGs increased 427% on average, with a trend of increase at early stage and decrease at later stage, and the main reduction stage appeared in maturity stage. The abundance of ARGs was mainly affected by the community succession of potential host bacteria. Composting could reduce the abundance of potential host bacteria of ARGs as well as pathogens such as Pseudomonas, and reduce the environmental risks of swine manure. N/C and S levels had a positive effect on the potential host of most ARGs. Prolonging the maturity period would inhibit the growth of potential host bacteria of ARGs during composting, therefore inhibiting the transmission of ARGs.202132971337
7063170.9985Impact of dairy manure pre-application treatment on manure composition, soil dynamics of antibiotic resistance genes, and abundance of antibiotic-resistance genes on vegetables at harvest. Manuring ground used for crop production is an important agricultural practice. Should antibiotic-resistant enteric bacteria carried in the manure be transferred to crops that are consumed raw, their consumption by humans or animals will represent a route of exposure to antibiotic resistance genes. Treatment of manures prior to land application is a potential management option to reduce the abundance of antibiotic resistance genes entrained with manure application. In this study, dairy manure that was untreated, anaerobically digested, mechanically dewatered or composted was applied to field plots that were then cropped to lettuce, carrots and radishes. The impact of treatment on manure composition, persistence of antibiotic resistance gene targets in soil following application, and distribution of antibiotic resistance genes and bacteria on vegetables at harvest was determined. Composted manure had the lowest abundance of antibiotic resistance gene targets compared to the other manures. There was no significant difference in the persistence characteristics of antibiotic resistance genes following land application of the various manures. Compared to unmanured soil, antibiotic resistance genes were detected more frequently in soil receiving raw or digested manure, whereas they were not in soil receiving composted manure. The present study suggests that vegetables grown in ground receiving raw or digested manure are at risk of contamination with manure-borne antibiotic resistant bacteria, whereas vegetables grown in ground receiving composted manure are less so.201728076772
6953180.9984Long-term biogas slurry application increased antibiotics accumulation and antibiotic resistance genes (ARGs) spread in agricultural soils with different properties. Animal manures are commonly applied to soil which possibly promote the spread of antibiotic resistance from soil to human beings via food chains. Biogas slurry is an end product of anaerobic digestion of animal manures, which has been widely applied as fertilizers in the agricultural soil. However, effect of long-term biogas slurry application on the soil antibiotic resistance and the associated mechanism still remains unclear. The present study characterized antibiotics, antibiotic resistance genes (ARGs), mobile genetic elements (MGEs) and bacterial community, in different agricultural soils unamended (BS-) and amended (BS+) with biogas slurry (8-18 years) in five field experiments. Our results indicated that long-term application of biogas slurry largely increased the concentrations of tetracyclines in soils, and greatly increased the abundances of ARGs, transposase gene (Tn916/1545) and ARGs-associated bacteria. Long-term application of biogas slurry led to tetracyclines accumulation and ARGs enrichment in agricultural soil, and the selection pressure from tetracyclines and the increase of Tn916/1545 abundace become potential contributors for the increase of soil antibiotic resistance via promoting the enrichment of ARG-associated bacteria. The results of the present study should be taken into consideration to develop policy and practice for mitigating the enrichment and spread of antibiotic resistance during the recycling of biogas slurry into agricultural soil.202133203566
7068190.9984Land application of sewage sludge: Response of soil microbial communities and potential spread of antibiotic resistance. The effect of land application of sewage sludge on soil microbial communities and the possible spread of antibiotic- and metal-resistant strains and resistance determinants were evaluated during a 720-day field experiment. Enzyme activities, the number of oligotrophic bacteria, the total number of bacteria (qPCR), functional diversity (BIOLOG) and genetic diversity (DGGE) were established. Antibiotic and metal resistance genes (ARGs, MRGs) were assessed, and the number of cultivable antibiotic- (ampicillin, tetracycline) and heavy metal- (Cd, Zn, Cu, Ni) resistant bacteria were monitored during the experiment. The application of 10 t ha(-1) of sewage sludge to soil did not increase the organic matter content and caused only a temporary increase in the number of bacteria, as well as in the functional and structural biodiversity. In contrast to expectations, a general adverse effect on the tested microbial parameters was observed in the fertilized soil. The field experiment revealed a significant reduction in the activities of alkaline and acid phosphatases, urease and nitrification potential. Although sewage sludge was identified as the source of several ARGs and MRGs, these genes were not detected in the fertilized soil. The obtained results indicate that the effect of fertilization based on the recommended dose of sewage sludge was not achieved.202133383416