Risk Of Antibiotic Resistance Genes Research Articles

Effects of antibiotic resistance genes on health risks of rivers in habitat of wild animals under human disturbance - based on analysis of antibiotic resistance genes and virulence factors in microbes of river sediments.

Studying the ecological risk of antibiotic resistance genes (ARGs) to wild animals from human disturbance (HD) is an important aspect of "One Health". The highest risk level of ARGs is reflected in pathogenic antibiotic-resistant bacteria (PARBs). Metagenomics was used to analyze the characteristics of PARBs in river sediments. Then, the total contribution of ARGs and virulence factors (VFs) were assessed to determine the health risk of PARBs to the rivers. Results showed that HD increased the diversity and total relative abundance of ARG groups, as well as increased the kinds of PARBs, their total relative abundance, and their gene numbers of ARGs and VFs. The total health risks of PARBs in wild habitat group (CK group), agriculture group (WA group), grazing group (WG group), and domestic sewage group (WS group) were 0.067 × 10-3, -1.55 × 10-3, 87.93 × 10-3, and 153.53 × 10-3, respectively. Grazing and domestic sewage increased the health risk of PARBs. However, agriculture did not increase the total health risk of the rivers, but agriculture also introduced new pathogenic mechanisms and increased the range of drug resistance. More serious was the increased transfer risk of ARGs in the PARBs from the rivers to wild animals under agriculture and grazing. If the ARGs in the PARBs are transferred from the rivers under HD to wild animals, then wild animals may face severe challenges of acquiring new pathogenic mechanisms and developing resistance to antibiotics. Further analysis showed that the total phosphorus (TP) and dissolved organic nitrogen (DON) were related to the risk of ARGs. Therefore, controlling human emissions of TP and DON could reduce the health risk of rivers.

A novel integrated microbial fuel cell-membrane bioreactor (MFC-MBR) for controlling the spread of antibiotic and antibiotic resistance genes while simultaneously alleviating membrane fouling

The dissemination of antibiotics and antibiotic resistance genes (ARGs) in the environment can potentially pose risks to ecosystems and human health. Herein, a novel microbial fuel cell and membrane bioreactor (MFC-MBR) integrated system characterized by internal reflux of sludge mixtures was proposed to reduce antibiotics, control the spread risk of antibiotic resistance genes (ARGs), and simultaneously alleviate membrane fouling. The bioelectricity production was distinctly promoted with increasing return flow ratios under sulfamethoxazole (SMX) addition. Besides, reactors characterized by higher return flow ratios achieved a relatively elevated degradation rate of SMX, attributed to the enhanced microbial activities through electrical stimulation. Importantly, the absolute abundance of intI1, sul1 and sul3 significantly decreased in the effluent of reactors characterized by higher return flow ratios. The value of zeta potential and particle size of sludge flocs subsequently increased and the content of membrane foulants dropped with the increasing return flow ratios. Moreover, MFC-MBRs characterized by higher return flow ratios were enriched in antibiotic degrading bacteria (Firmicutes, Thauera) and electrochemically active bacteria (Proteobacteria, Bacteroidota). Therefore, this study provided a theoretical basis for reducing the spread of antibiotics and ARGs while simultaneously alleviating fouling, achieving the best of both worlds, through the novel MFC-MBR integrated system.

New insights into bioaugmented removal of sulfamethoxazole in sediment microcosms: degradation efficiency, ecological risk and microbial mechanisms

BackgroundBioaugmentation has the potential to enhance the ability of ecological technology to treat sulfonamide-containing wastewater, but the low viability of the exogenous degraders limits their practical application. Understanding the mechanism is important to enhance and optimize performance of the bioaugmentation, which requires a multifaceted analysis of the microbial communities. Here, DNA-stable isotope probing (DNA-SIP) and metagenomic analysis were conducted to decipher the bioaugmentation mechanisms in stabilization pond sediment microcosms inoculated with sulfamethoxazole (SMX)-degrading bacteria (Pseudomonas sp. M2 or Paenarthrobacter sp. R1).ResultsThe bioaugmentation with both strains M2 and R1, especially strain R1, significantly improved the biodegradation rate of SMX, and its biodegradation capacity was sustainable within a certain cycle (subjected to three repeated SMX additions). The removal strategy using exogenous degrading bacteria also significantly abated the accumulation and transmission risk of antibiotic resistance genes (ARGs). Strain M2 inoculation significantly lowered bacterial diversity and altered the sediment bacterial community, while strain R1 inoculation had a slight effect on the bacterial community and was closely associated with indigenous microorganisms. Paenarthrobacter was identified as the primary SMX-assimilating bacteria in both bioaugmentation systems based on DNA-SIP analysis. Combining genomic information with pure culture evidence, strain R1 enhanced SMX removal by directly participating in SMX degradation, while strain M2 did it by both participating in SMX degradation and stimulating SMX-degrading activity of indigenous microorganisms (Paenarthrobacter) in the community.ConclusionsOur findings demonstrate that bioaugmentation using SMX-degrading bacteria was a feasible strategy for SMX clean-up in terms of the degradation efficiency of SMX, the risk of ARG transmission, as well as the impact on the bacterial community, and the advantage of bioaugmentation with Paenarthrobacter sp. R1 was also highlighted.8sNhd6qoUNMdHWMUGzd-tFVideo

Long-term effect of microplastics on anammox systems: From macro efficiency to micro metabolic mechanisms and antibiotic resistance genes proliferation

Wastewater treatment plants (WWTPs) are sinks for various types of microplastics (MPs), which have an undeniable impact on anaerobic ammonia oxidation (anammox) systems, yet their differential effects remain elusive. In this study, the long-term effects of non-biodegradable polyvinyl chloride (PVC) MPs and biodegradable polylactic acid (PLA) MPs in anammox systems were investigated from macro efficiency, micro metabolic mechanism, and antibiotic resistance gene proliferation. Results showed that the introduced 0.5 mg L−1 PVC MPs caused a 20.64 % decrease in nitrogen removal efficiency (NRE) compared to the control one, while PLA MPs resulted in a 10.73 % increase in NRE. Accordingly, the relative abundance of Ca. Kuenenia with the introduced PLA MPs was 16.68 % higher than the control group, while it was 10.89 % lower with the introduced PVC MPs. Furthermore, MPs inhibit the reactor performance by inducing intracellular reactive oxygen species (ROS) production in anammox cells. However, PLA MPs, as a slow biodegradable organic, have a reversible negative effect on ROS induction, which further improves nitrogen removal performance and sludge proliferation through dissimilatory nitrate reduction to ammonium (DNRA) and microbial interactions. Nevertheless, this also poses an increased risk of antibiotic resistance genes (ARGs) spread and proliferation in anammox sludge. This study clarified the comprehensive effects of different MPs types in anammox processes, highlighting the feasibility and potential risks in the engineering applications of anammox processes for MPs-contained wastewater treatment.

Long-term occurrence, resistance risk and chaotic characteristics of antibiotic resistance genes in sludge anaerobic digestion system

The long-term occurrence, dynamics and risk of antibiotic resistance genes (ARGs) in anaerobic digestion (AD) of excess sludge (ES) are not fully understood. Therefore, 13-month metagenomic monitoring was carried out in a full-scale AD plant. The highest ARG abundance and risk scores were observed in spring. AD achieved a 35 % removal rate for the total ARG abundance, but the risk score of AD sludge was not always lower than ES samples, because of the higher proportion of Rank I ARGs in AD sludge. ARGs showed less obvious patterns under linear models compared with microbial community, implying their chaotic dynamics, which was further confirmed by nonlinearity tests. Empirical dynamic modeling performed better than the autoregressive integrated moving average model for ARG dynamics, especially for those with simple and nonlinear dynamics. This study highlighted spring for its higher ARG abundance and risk, and recommended nonlinear models for revealing the dynamics of ARGs.

Hazardous risk of antibiotic resistance genes: Host occurrence, distribution, mobility and vertical transmission from different environments to corn silage

Antibiotic resistance genes (ARGs) are one of the emerging contaminants posing a great deal of hazardous risk to public health. This study employed metagenomics and deciphered the potential risk of the antibiotic resistome and their vertical transfer to ensiled whole-crop corn silage harvested from six climate zones: 1. Warm temperate-fully humid-hot summer (Cfa), 2. Arid-desert-cold arid (BWk), 3. Snow-desert-cold summer (Dwc), 4. Snow-desert-hot summer (Dwa), 5. Arid-steppe-cold arid (BSk), and 6. Equatorial-desert (Aw) based on the Köppen-Geiger climate classification in China. The findings demonstrate a high diversity of ARGs, which is related to the drug classes of tetracycline, ciprofloxacin, lincosamide, fosfomycin, and beta lactam. Resistome variations are mostly related to variations in microbial composition and fermentation characteristics of the silages from different climate zones, which are indirectly influenced by environmental conditions. The most dominating ARGs in corn silage were tetM, acrA, H-NS, lnuA, emrR, and KpnG, which is primarily hosted by Klebsiella and Lactobacilli. There were 5 high-risk ARGs (tetM, bacA, SHV-1, dfrA17, and QnrS1) in silage from different climate zones, and the tetM was the most prevalent high-risk ARG. However, throughout the ensiling process, the abundance of ARGs, and mobile ARGs were reduced. The resistome contamination in silage from Tibet (Dwc) with high altitude and harsh environment was relatively low due to the low variety and abundance of ARGs, the low abundance of mobile ARGs and high-risk ARGs. In addition, most of the bacteria responsible for the silage fermentation were also found to be the hosts to the ARGs, although their abundance decreased after 90 d of silage fermentation. Hence, we alert the existence of ARGs-related biosafety risk in silages and call for more attention to the silage ARGs, their hosts, and mobile genetic elements in order to curtail their possible risk to public health.

Copper in different forms and tetracycline affect behavior and risk of antibiotic resistome in thermophilic anaerobic digestion of cattle manure.

The metagenomics-based behavior and risk of antibiotic resistance genes (ARGs) were investigated during cattle manure thermophilic anaerobic digestion with tetracycline and copper, namely, bulk-copper oxide, nano-copper oxide, and copper sulfate, which are common feed additives. Although bulk-copper oxide reduced ARGs' diversity, it enriched high-risk ARGs the most than the other two copper species, while copper sulfate could strongly mitigate the ARG risk by decreasing their abundances. Compared to corresponding individual effects, copper and tetracycline combinations may decrease ARGs' co-occurrence potential by 22.0%, and particularly, tetracycline combined separately with copper sulfate and nano-copper oxide reduces the ARGs' risk in abundance (by 7.2%) and human health (by 4.0%). These were mainly driven by bioavailable copper, volatile fatty acids, and pH, as well as the main potential hosts in phyla Firmicutes, Coprothermobacterota, and Euryarchaeota. Notably, the twin risks of pathogenicity and ARGs should be emphasized due to the ARGs' positive correlation with human pathogens of Clostridioides difficile and Arcobacter peruensis. These findings are important for understanding the potential ARGs' risk in treatments of livestock wastes containing feed additives of different sizes and speciation.

Spatiotemporal dynamics, traceability analysis, and exposure risks of antibiotic resistance genes in PM2.5 in Handan, China.

Fine particulate matter (PM2.5) seriously affects environmental air quality and human health, and antibiotic resistance genes (ARGs) in PM2.5 posed a great challenge to clinical medicine. The year of 2013-2017 was an important 5-year period for the implementation of Air Pollution Prevention and Control Action Plan (APPCAP) in China. Here, we took Handan, a PM2.5 polluted city in northern China, as the research object and analyzed ARGs in PM2.5 in winter (January) from 2013 to 2017. The results showed that the abundance of ARGs was the highest in 2013 (3.7 × 10-2 copies/16S rRNA), and ARGs were positively correlated with air quality index (AQI) (r = 0.328, P < 0.05) and PM2.5 concentration (r = 0.377, P = 0.020 < 0.05) in the 5-year period. The ARGs carried by PM2.5 in four functional regions of sewage treatment plant, steel works, university, and park showed that sul1 and qepA had higher abundance in each functional region, and the total ARG abundance in sewage treatment plant (1.3 × 10-1 copies/16S rRNA) was the highest, while lowest in park (2.0 × 10-3 copies/16S rRNA). Potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) model were used to trace the pollutants at the sampling points, which indicated that the surrounding cities contributed more than quarter to the sampling points. Therefore, regional transportation reduces the spatial distribution difference of ARGs in PM2.5. The exposure dose of ARGs in different functional regions illustrated that the total inhaled dose of ARGs in sewage treatment plant (1.7 × 105 copies/d) was the highest, while lowest in park (3.2 × 104 copies/d). This study is of great significance for assessing the distribution and sources of ARGs under the clean air initiative in China.

Removal of oxytetracycline and sulfamethoxazole in vertical down-up flow constructed wetlands: Efficiency, removal pathways, and occurrence of antibiotic resistance genes

The extensive use of antibiotics leads to their frequent detection in the environment, posing potential threats to public health. Constructed wetlands (CWs) have been widely applied in wastewater treatment and can efficiently remove antibiotics. However, the removal of antibiotics in the CWs is still in a “black box”, and the information about the potential risks of antibiotic resistance genes (ARGs) occurrence in CWs is limited. In the present study, the removal of oxytetracycline (OTC) and sulfamethoxazole (SMZ), as well ARGs occurrence in vertical down-up flow constructed wetlands (VDUF-CWs) were assessed. The results indicated that VDUF-CWs exhibited great removal efficiency for OTC (84.3 ± 3.5 %) and SMZ (77.7 ± 3.9 %). Based on conservation of mass, the contributions of different removal pathways (i.e., microbial degradation, plant absorption, photodegradation, and substrate adsorption) to antibiotic removal were calculated. Of which, microbial degradation was found to be the dominant route in removing OTC and SMZ with the contribution of 58.52 ± 2.34 % and 65.13 ± 3.72 % respectively, followed by photodegradation (18.47 ± 3.04 % and 8.22 ± 3.94 %), plant absorption (9.01 ± 1.28 % and 7.75 ± 4.07 %) and substrate adsorption (2.08 ± 0.03 % and 1.73 ± 0.02 %). Notably, tetA, tetC, tetW, sulI, and sulII genes were detected in layer samples, and the relative abundances of the sul and tet genes were boosted with the extension of operation days, indicating that VDUF-CWs allow a risk of ARGs spread and threatening public health. The present study provided a deeper insight into the mechanism of antibiotic removal in CWs, but further explorations are required to develop the effective control strategies for eliminating ARGs from CWs.

Biodegradation of soil agrochemical contamination mitigates the direct horizontal transfer risk of antibiotic resistance genes to crops

Microorganisms can drive a substrate-specific biodegradation process to mitigate soil contamination resulting from extensive agrochemical usage. However, microorganisms with high metabolic efficiency are capable of adapting to the co-occurrence of non-substrate contaminants in the soil (particularly antibiotics). Therefore, the utilization of active microorganisms for biodegradation raises concerns regarding the potential risk of antibiotic resistance development. Here, the horizontal transfer risk of antibiotic-resistance genes (ARGs) in the soil-plant biota was assessed during biodegradation by the newly isolated Proteus terrae ZQ02 (which shortened the half-life of fungicide chlorothalonil from 9.24 d to 2.35 d when exposed to tetracycline). Based on metagenomic analyses, the distribution of ARGs and mobile genetic elements (MGEs) was profiled. The ARGs shared with ∼118 core genes and mostly accumulated in the rhizosphere and maize roots. After ZQ02 was inoculated, the core genes of ARGs reduced significantly in roots. In addition, the Pseudomonas and Proteus genera were identified as the dominant microbial hosts of ARGs and MGEs after ZQ02 adoption. The richness of major ARG hosts increased in soil but barely changed in the roots, which contributed to the mitigation of hosts-mediated ARGs transfer from soil to maize. Finally, the risk of ARGs has been assessed. Compared with the regular planting system, the number of risky ARGs declined from 220 (occupied 4.77 % of the total ARGs) to 143 (occupied 2.67 %) after biodegradation. Among these, 23 out of 25 high-risk genes were aggregated in the soil whereas only 2 genes were identified in roots, which further verified the low antibiotic resistance risk for crop after biodegradation. In a nutshell, this work highlights the critical advantage of ZQ02-based biodegradation that alleviating the ARGs transfer risks from soil to crop, which offers deeper insights into the versatility and feasibility of bioremediation techniques in sustainable agriculture.

Atmospheric antibiotic resistome driven by air pollutants

The atmosphere is an important reservoir and habitat for antibiotic resistance genes (ARGs) and is a main pathway to cause potential health risks through inhalation and ingestion. However, the distribution characteristics of ARGs in the atmosphere and whether they were driven by atmospheric pollutants remain unclear. We annotated 392 public air metagenomic data worldwide and identified 1863 ARGs, mainly conferring to tetracycline, MLS, and multidrug resistance. We quantified these ARG's risk to human health and identified their principal pathogenic hosts, Burkholderia and Staphylococcus. Additionally, we found that bacteria in particulate contaminated air carry more ARGs than in chemically polluted air. This study revealed the influence of typical pollutants in the global atmosphere on the dissemination and risk of ARGs, providing a theoretical basis for the prevention and mitigation of the global risks associated with ARGs.

Purification of aquaculture wastewater by macrophytes and biofilm systems: Efficient removal of trace antibiotics and enrichment of antibiotic resistance genes

The purification performance of aquaculture wastewater and the risk of antibiotic resistance genes (ARGs) dissemination in wetlands dominated by macrophytes remain unclear. Here, the purification effects of different macrophytes and biofilm systems on real aquaculture wastewater were investigated, as well as the distribution and abundance of ARGs. Compared to the submerged macrophytes, artificial macrophytes exhibited higher removal rates of TOC (58.80 ± 5.04 %), TN (74.50 ± 2.50 %), and TP (77.33 ± 11.66 %), and achieved approximately 79.92 % removal of accumulated trace antibiotics in the surrounding water. Additionally, the biofilm microbial communities on the surface of artificial macrophytes exhibited higher microbial diversity with fewer antibiotic-resistant bacteria (ARB) enrichment from the surrounding water. The absolute abundance of ARGs (sul1, sul2, and intI1) in the mature biofilm to be one to two orders of magnitude higher than that in the water. Although biofilms could decrease ARGs in the surrounding water by enriching ARB, the intricate network structure of biofilms further facilitated the proliferation of ARB and the dissemination of ARGs in water. Network analysis suggested that Proteobacteria and Firmicutes phyla were dominant and potential carriers of ARGs, contributing 69.00 % and 16.70 %, respectively. Our findings highlight that macrophytes and biofilm systems have great performance on aquaculture wastewater purification, but with high risk of ARGs.

Unraveling antibiotic resistomes associated with bacterial and viral communities in intertidal mudflat aquaculture area

The extensive use of antibiotics in intertidal mudflat aquaculture area has substantially increased the dissemination risk of antibiotic resistance genes (ARGs). As hosts of ARGs, bacteria and virus exert vital effects on ARG dissemination. However, the insights for the interrelationships among ARGs, bacteria, and virus have not been thoroughly explored in intertidal mudflat. Therefore, this study attempts to unravel the occurrence, dissemination, evolution, and driving mechanisms of ARGs associated with bacterial and viral communities using metagenomic sequencing in a typical intertidal mudflat. Abundant and diverse ARGs (22 types and 437 subtypes) were identified and those of ARGs were higher in spring than in autumn. It is worthy noted that virus occupied a more essential position than bacteria for ARGs dissemination through network analysis. Meanwhile, nitrogen exerted indirect effect on ARG profiles by shaping viral and bacterial diversity. According to the results of neutral and null models, deterministic processes dominated the ARG community assembly by controlling sediment nitrogen and antibiotics. Homogeneous and variable selection dominated phylogenetic turnover of ARG community, contributing 46.15% and 45.90% of the total processes, respectively. This study can hence theoretically support for the ARG pollution control and management in intertidal mudflat aquaculture area.

Spatial distribution, pollution characteristics, and health risks of antibiotic resistance genes in China: a review

Spatial distribution, pollution characteristics, and health risks of antibiotic resistance genes in China: a review

Environmental risks of antibiotic resistance genes released from biological laboratories and its control measure.

Antibiotic resistance genes (ARGs) are a growing global threat to public health. Biological laboratory wastewater contains large amounts of free ARGs. It is important to assess the risk of free ARGs from biological laboratories and to find appropriate treatments to control their spread. The fate of plasmids in the environment and the effect of different thermal treatments on their persistence activity were tested. The results showed that untreated resistance plasmids could exist in water for more than 24h (the special 245bp fragment). Gel electrophoresis and transformation assays showed that the plasmids boiled for 20min retained 3.65% ± 0.31% transformation activity of the intact plasmids, while autoclaving for 20min at 121°C could effectively degrade the plasmids and that NaCl, bovine serum albumin, and EDTA-2Na affected the degradation efficiency of the plasmids during boiling. In the simulated aquatic system, using 106 copy/μL of plasmids after autoclaving, only 102 copies/μL of the fragment after only 1-2h could be detected. By contrast, boiled plasmids for 20min were still detectable after plunging them into water for 24h. These findings suggest that untreated and boiled plasmids can remain in the aquatic environment for a certain time resulting in the risk of disseminating ARGs. However, autoclaving is an effective way of degrading waste free resistance plasmids.

The environmental risk of antibiotic resistance genes from manure compost fertilizer gradually diminished during ryegrass planting

As one of the emerging pollutants in the environment, antibiotic resistance genes (ARGs) have attracted much attention. Composting is an effective way to reduce ARGs and the compost products were often used as soil amendments. However, the environmental risk of ARGs from compost products to soil and plants has not been well studied. Here, we assessed the environmental risk of ARGs from soil and ryegrass after applying manure composting. This study detected 21 different types of ARGs. Multidrug and tetracycline resistance genes were the most dominant ones, accounting for 39.2%/12.5% and 38.6%/11.6% in soil/ryegrass, respectively. This might be attributed to the decrease of Streptomyces, which is the potential host of multidrug and tetracycline ARGs. The environmental risk value, which was associated with mobile genetic elements (MGEs) and pathogens, increased in the soil and ryegrass, and return to the original level at the end of the growth cycle. The absolute environmental risk values of AH (high additive amount of the swine manure compost) and BH (high additive amount of the sheep manure compost) decreased by 0.0826 and 0.1505, respectively. The outcomes of this study revealed the environmental behavior and risk of ARGs transferring from compost to soil, and then entering into ryegrass, which is important to assess the environmental risk of compost and provide new insights into agricultural food safety.

Quantification of the mobility potential of antibiotic resistance genes through multiplexed ddPCR linkage analysis.

There is a clear need for global monitoring initiatives to evaluate the risks of antibiotic resistance genes (ARGs) towards human health. Therefore, not only ARG abundances within a given environment, but also their potential mobility, hence their ability to spread to human pathogenic bacteria needs to be quantified. We developed a novel, sequencing-independent method for assessing the linkage of an ARG to a mobile genetic element by statistical analysis of multiplexed droplet digital PCR (ddPCR) carried out on environmental DNA sheared into defined, short fragments. This allows quantifying the physical linkage between specific ARGs and mobile genetic elements, here demonstrated for the sulfonamide ARG sul1 and the Class 1 integron integrase gene intI1. The method's efficiency is demonstrated using mixtures of model DNA fragments with either linked and unlinked target genes: Linkage of the two target genes can be accurately quantified based on high correlation coefficients between observed and expected values (R2) as well as low mean absolute errors (MAE) for both target genes, sul1 (R2 = 0.9997, MAE = 0.71%, n = 24) and intI1 (R2 = 0.9991, MAE = 1.14%, n = 24). Furthermore, we demonstrate that adjusting the fragmentation length of DNA during shearing allows controlling rates of false positives and false negative detection of linkage. The presented method allows rapidly obtaining reliable results in a labor- and cost-efficient manner.

Effects of micron-scale zero valent iron on behaviors of antibiotic resistance genes and pathogens in thermophilic anaerobic digestion of waste activated sludge

This work investigated the metagenomics-based behavior and risk of antibiotic resistance genes (ARGs), and their potential hosts during thermophilic anaerobic digestion (TAD) of waste activated sludge, enhanced by micron-scale zero valent iron (mZVI). Tests were conducted with 0, 25, 100, and 250 mg mZVI/g total solids (TS). Results showed that up to 7.3% and 4.8% decrease in ARGs’ abundance and diversity, respectively, were achieved with 100 mg mZVI/g TS. At these conditions, ARGs with health risk in abundance and human pathogenic bacteria (HPB) diversity were also decreased by 8.3% and 3.6%, respectively. Additionally, mZVI reduced abundance of 72 potential pathogenic supercarriers for ARGs with high health risk by 2.5%, 5.0%, and 6.1%, as its dosage increased. Overall, mZVI, especially at 100 mg/g TS, can mitigate antibiotic resistance risk in TAD. These findings are important for better understanding risks of ARGs and their pathogenic hosts in ZVI-enhanced TAD of solid wastes.

Iron-modified peat and magnetite-pine bark biosorbents for levofloxacin and trimethoprim removal from synthetic water and various pharmaceuticals from real wastewater

Humans are at significant risk of antibiotic resistance genes (ARGs) and antimicrobial resistance (AMR) via exposure to pharmaceutical contaminants in water, so there is a strong need for cost-effective environmental solutions to mitigate this crisis. This study introduces iron-modified peat and magnetite-pine bark as efficient, low-cost and green biosorbents for the adsorption of pharmaceutical contaminants from wastewater. Peat biomass, modified by iron extracted from a groundwater treatment sludge was dissolved in acid to prepare the iron-modified peat biosorbent, and pine (Pinus sylvestris) bark as a forest industry by-product was mixed with iron salts (Fe3+: Fe2+ = 2:1) to obtain the magnetite biosorbent. The adsorption of levofloxacin was little influenced by pH compared to trimethoprim. The equilibrium removal efficiency of antibiotics over both biosorbents was reached after 180 min contact time. The maximum adsorption capacity over iron-modified peat was about 200 mg/g for both antibiotics and over magnetite-pine bark 153.0 mg/g for levofloxacin and 184.1 mg/L for trimethoprim. Possible antibiotic adsorption mechanisms were proposed based on the Fourier transform infrared spectroscopy (FTIR) analysis. Experiments with real wastewater effluent revealed trimethoprim removal of 56.6–84.3% (dosage: 3 g/L). Moreover, a variety of other pharmaceuticals were removed by the biosorbents.

Composting reduces the risks of antibiotic resistance genes in maize seeds posed by gentamicin fermentation waste

Using high-throughput quantitative PCR and next generation sequencing, the impact of land application of raw and composted gentamicin fermentation waste (GFW) on antibiotic resistance genes (ARGs) in maize seeds was studied in a three-year field trial. The raw and composted GFW changed both the bacterial community composition and the ARGs diversity in the maize seeds compared to non-amended controls and chemical fertilizer. The abundance of ARGs after raw GFW amendment was significantly higher than other treatments because of a high abundance of aadA1, qacEdeltal and aph(2′)-Id-02; probably induced by gentamicin selection pressure in maize tissues. Meanwhile, the potential host of these three ARGs, pathogenic bacteria Tenacibaculum, also increased significantly in maize seeds after the application of raw GFW. But our result proved that composting could weaken the risk posed by GFW. We further reveal that the key biotic driver for shaping the ARG profiles in maize seeds is bacterial community followed by heavy metal resistance genes, and ARGs are more likely located on bacterial chromosomes. Our findings provide new insight into ARGs dispersal mechanism in maize seeds after long-term GFW application, demonstrate the potential benefits of composting the GFW to reduce risks as well as the potential efficient management method to GFW.