Levels Of Antibiotic Resistance Genes Research Articles

Common and management-specific responses of grassland soil bacterial communities to manure and chlortetracycline amendments

Manure application to soil affects the composition of soil bacterial communities as well as levels of antibiotic resistance genes in a manner dependent on various environmental and agricultural factors. These effects have been widely studied in arable soils, while the situation in grasslands that also receive inputs of fresh animal manure is largely unknown. Here, we focused on grassland soils under three different management types (pristine meadow, pasture, wintering pasture) from the same locality and compared the response of their bacterial communities to fresh cattle manure spiked or not with chlortetracycline. Soil microcosms were established either with soils (controls), + manure, + manure and chlortetracycline (CTC, 0.2 mg kg−1), and sampled at the same day (t0) and after 28 days (t28). Bacterial community composition was assessed by 454-pyrosequencing of 16S rRNA genes and correlations between the abundance of bacterial taxa and chosen tetracycline resistance genes (measured in our previous study) were calculated. Control soil bacterial communities at t0 differed significantly, reflecting differences in soil management history. Despite these initial differences, the responses of soil bacterial communities to cattle manure amendment showed similar trends in all three soils. Fresh cattle manure amendments significantly modified bacterial community structure in all soils at t0, increasing the relative abundance of OTUs affiliated to Clostridia and Bacilli. At 28d, all manure-amended soils showed a partial resilience, though they remained significantly different from controls. The effect of additional CTC was comparatively lower and only significant at t0 in all three soils. Several members of Firmicutes showed strong positive correlation with the abundance of tetracycline resistance genes tet(O), tet(Q) and tet(W), indicating that these taxa are potentially involved in dissemination of tetracycline resistance in manure-treated soils. In addition, this study indicated certain soil-management specific taxa, such as Geothrix and uncultured Burkholderiaceae, which could explain the previously observed differences in persistence of tetracycline resistance genes among soils.

Spread of antibiotic resistance genes and microbiota in airborne particulate matter, dust, and human airways in the urban hospital

Antimicrobial resistance is an increasingly serious threat to public health worldwide. The presence of antibiotic resistance genes (ARGs) in human airways and relevant environments has not received significant attention. In this study, abundances of ARGs and microbes from airborne particulate matter, dust, and human airways in a hospital were profiled using high-throughput qPCR and 16S rRNA gene sequencing. More diverse ARGs and microbes in indoor dust and higher levels of ARGs in particulate matter PM10 and PM2.5 were observed. Macrolides and aminoglycoside resistance genes were the most abundant ARGs in the airway and environmental samples, respectively. Moreover, the co-occurrences of priority pathogens, ARGs, and mobile genetic elements (MGEs) were shown by the Network analysis. Campylobacter spp. and Staphylococcus spp. positively correlated with fluoroquinolone (vatC-02, mexD) and β-lactams (blaZ, mecA) resistance genes, respectively. In this regard, based on SourceTracker analysis, inhalable particles contributed to 4.0% to 5.5% of ARGs in human airway samples, suggesting an important exchange between airborne inhalable particles and human commensals. This study may advance knowledge about ARGs in airborne particulate matter and dust associated environments, reveal their potential link between environments and humans, and provide a new sight and fundamental data for ARG risk assessment.

Unraveling the riverine antibiotic resistome: The downstream fate of anthropogenic inputs

River networks are one of the main routes by which the public could be exposed to environmental sources of antibiotic resistance, that may be introduced e.g. via treated wastewater. In this study, we applied a comprehensive integrated analysis encompassing mass-flow concepts, chemistry, bacterial plate counts, resistance gene quantification and shotgun metagenomics to track the fate of the resistome (collective antibiotic resistance genes (ARGs) in a microbial community) of treated wastewater in two Swiss rivers at the kilometer scale. The levels of certain ARGs and the class 1 integron integrase gene (intI1) commonly associated with anthropogenic sources of ARGs decreased quickly over short distances (2-2.5 km) downstream of wastewater discharge points. Mass-flow analysis based on conservative tracers suggested this decrease was attributable mainly to dilution but ARG loadings frequently also decreased (e.g., 55.0-98.5 % for ermB and tetW) over the longest studied distances (6.8 and 13.7 km downstream). Metagenomic analysis confirmed that ARG of wastewater-origin did not persist in rivers after 5 ~ 6.8 km downstream distance. sul1 and intI1 levels and loadings were more variable and even increased sharply at 5 ~ 6.8 km downstream distance on one occasion. While input from agriculture and in-situ positive selection pressure for organisms carrying ARGs cannot be excluded, in-system growth of biomass is a more probable explanation. The potential for direct human exposure to the resistome of wastewater-origin thus appeared to typically abate rapidly in the studied rivers. However, the riverine aquatic resistome was also dynamic, as evidenced by the increase of certain gene markers downstream, without obvious sources of anthropogenic contamination. This study provides new insight into drivers of riverine resistomes and pinpoints key monitoring targets indicative of where human sources and exposures are likely to be most acute.

Fish farm effluents as a source of antibiotic resistance gene dissemination on Jeju Island, South Korea.

The abuse or misuse of antibiotics is directly linked to the emergence of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) in the environment. Most fish farms located on Jeju Island operate a flow-through system that pumps in seawater for fish farming and discharges it back to the ocean. To investigate the amount of ARGs that these fish farm effluents discharge into the marine environment, we conducted a metagenomic-based resistome analysis. We observed higher levels of ARGs in fish farm effluents than in seawater at beach and residential areas. A greater proportion of ARGs was found on plasmid rather than on chromosomal DNA, especially for sulfonamide and phenicol classes. The distribution of ARGs did not differ between summer and winter, but the microbial community did. In addition, fish farm samples contained significantly more opportunistic pathogens (i.e., Vibrio, Photobacterium, Aliivibrio, and Tenacibaculum) and virulence factors than non-fish farm samples. Vibrio was the most frequently identified host of ARGs and virulence factors. The presence of Vibrio in the coastal area has been increasing owing to the recent rise in the temperature of seawater. This study suggests the need for actions to treat or monitor ARGs in the coastal areas where fish farms operating a flow-through system are located.

Diverse and abundant antibiotic resistance genes in mangrove area and their relationship with bacterial communities - A study in Hainan Island, China.

Antibiotic resistance genes (ARGs) are emerging contaminants in the environment and have been highlighted as a worldwide environmental and health concern. As important participants in the biogeochemical cycles, mangrove ecosystems are subject to various anthropogenic disturbances, and its microbiota may be affected by various contaminants such as ARGs. This study selected 13 transects of mangrove-covered areas in Hainan, China for sediment sample collection. The abundance and diversity of ARGs and mobile genetic elements (MGEs) were investigated using high-throughput quantitative polymerase chain reaction (HT-qPCR), and high-throughput sequencing was used to study microbial structure and diversity. A total of 179 ARGs belonging to 9 ARG types were detected in the study area, and the detection rates of vanXD and vatE-01 were 100%. The abundance of ARGs was 8.30×107-6.88×108 copies per g sediment (1.27×10-2-3.39×10-2 copies per 16S rRNA gene), which was higher than similar studies, and there were differences in the abundance of ARGs in these sampling transects. The multidrug resistance genes (MRGs) accounted for the highest proportion (69.0%), which indicates that the contamination of ARGs in the study area was very complicated. The ARGs significantly positively correlated with MGEs, which showed that the high level of ARGs was related to its self-enhancement. The dominant bacteria at the genus level were Desulfococcus, Clostridium, Rhodoplanes, Bacillus, Vibrio, Enterococcus, Sedimentibacter, Pseudoalteromonas, Paracoccus, Oscillospira, Mariprofundus, Sulfurimonas, Aminobacterium, and Novosphingobium. There was a significant positive correlation between 133 bacterial genera and some ARGs. Chthoniobacter, Flavisolibacter, Formivibrio, Kaistia, Moryella, MSBL3, Perlucidibaca, and Zhouia were the main potential hosts of ARGs in the sediments of Hainan mangrove area, and many of these bacteria are important participants in biogeochemical cycles. The results contribute to our understanding of the distribution and potential hosts of ARGs and provide a scientific basis for the protection and management of Hainan mangrove ecosystem.

A Meta-Analysis Reveals that Operational Parameters Influence Levels of Antibiotic Resistance Genes During Anaerobic Digestion of Animal Manures

A Meta-Analysis Reveals that Operational Parameters Influence Levels of Antibiotic Resistance Genes During Anaerobic Digestion of Animal Manures

On-farm screw press and rotary drum treatment of dairy manure-associated antibiotic residues and resistance.

An on-farm solid-liquid separator (SLS) and rotary drum composter (RD) manure treatment system was monitored for its impact on antibiotic residues and antibiotic resistance genes (ARGs). Administered antibiotics were tracked, and treatment system mass flows were quantified. Total amounts of antibiotic residues and ARGs were calculated from measured concentrations and mass flows. Only oxytetracycline (OTC) and sulfadimethoxine (SDM) were detected in the manure treatment system influent. No β-lactams were measured despite comprising ∼25% of the antibiotics administered. Nearly 80% of OTC and>90% of SDM partitioned into SLS liquid effluent (SL). The RD reduced the mass of OTC remaining in the SLS solid effluent (SS) significantly by 50%, whereas the mass of SDM appeared to increase after RD treatment. All four ARGs tested were detected in influent, with>70% of the sul1, blaOXA-1 , and intI1 genes (normalized by the 16S ribosomal RNA gene) partitioning into the SL. In contrast, about eight times more normalized tetO gene copies partitioned into the SS than in the SL. All ARGs remaining in the SS were significantly reduced by the RD treatment, with a noteworthy 98% reduction in normalized tetO gene copies. This study provides insight into on-farm levels of antibiotic residues and ARGs in dairy manure, their partitioning during SLS treatment, and their fate after a high-temperature RD treatment reaching 72.2 ± 0.18 °C near the outlet. It also notes the importance of mass-flow standardization of data, and the need to work towards standardization of manure system sampling protocols for antibiotic residues and ARGs.

Fate of antibiotics and antibiotic resistance genes in home water purification systems

Home water purification systems (HWPSs) are utilized worldwide to obtain clean drinking water. However, the reliability of HWPSs in providing safe water is unknown or not well-proven. In this study, the occurrences of antibiotics and antibiotic resistance genes (ARGs) in tap water, effluents, and filters of HWPSs were investigated in twenty-six houses and one laboratory. The levels of antibiotics and ARGs were between less than the limit of detection (LOD) and 7.9 ng/L and between less than LOD and 3.45 × 105 copies/L, respectively, in tap water. HWPSs with fresh filters had a high efficiency in removing antibiotics and ARGs, with removal rates of 91–92% and 0.46–2.43 log, respectively. However, after long-term operation (e.g., more than three months), some HWPSs had low removal rates of antibiotics and ARGs (3–79% and 0.03–0.15 log, respectively) and some HWPSs released antibiotics and ARGs into the effluents leading to higher levels of antibiotics and ARGs in the effluents than those in the influents. Biofilms were observed on many filters of the investigated HWPSs. ARGs were detected on the filters with relative abundances (the ratio of the abundance of ARGs to the abundance of 16S rRNA) of 2.56 × 10−8–2.89 × 10−2. High-throughput sequencing analysis showed that Proteobacteria, Acidobacteria, Chloroflexi, and Bacteroidetes were the dominant phyla, and Alphaproteobacteria and Gammaproteobacteria were the dominant classes. The abundances of Cyanobacteria, Patescibacteria, Bacteroidetes, and Proteobacteria were significantly positively correlated with the abundances of ARGs. Microbial growth and enrichment commonly observed in HWPSs can accelerate the exposure risk posed by antibiotics and ARGs to the consumers of water from these appliances.

Fates of Antibiotic Resistance Genes in the Gut Microbiome from Different Soil Fauna under Long-Term Fertilization.

Applying organic fertilizers has been well documented to facilitate the dissemination of antibiotic resistance genes (ARGs) in soil ecosystems. However, the role of soil fauna in this process has been seldom addressed, which hampers our ability to predict the fate of and to manage the spread of ARGs. Here, using high-throughput quantitative polymerase chain reaction (HT-qPCR), we examined the effect of long-term (5-, 8-, and 10-year) fertilization treatments (control, inorganic fertilizers, and mixed fertilizers) on the transfer of ARGs between soil, nematodes, and earthworms. We found distinct fates for ARGs in the nematodes and earthworms, with the former having higher enriched levels of ARGs than the latter. Fertilization impacted the number and abundance of ARGs in soil, and fertilization duration altered the composition of ARGs. Shared ARGs among soil, nematodes, and earthworm guts supported by a fast expectation-maximization microbial source tracking analysis demonstrated the trophic transfer potential of ARGs through this short soil food chain. The transfer of ARGs was reduced by fertilization duration, which was mainly ascribed to the reduction of ARGs in the earthworm gut microbiota. This study identified the transfer of ARGs in the soil-nematode-earthworm food chain as a potential mechanism for a wider dissemination of ARGs in the soil ecosystem.

Prevalence of antibiotic resistance genes in wastewater collected from ornamental fish market in northern China.

Large amounts of antibiotics/disinfectants are used in the farming of ornamental fish so as to prevent and treat bacterial infection. This may exert considerable selection pressures on the prevalence and propagation of antibiotic resistance genes (ARGs). However, the levels of ARGs and their potential prevalence mechanism in the wastewater of the ornamental fish industry remains unclear. In this work, wastewater is collected from a representative ornamental fish market (OFM) that is located at the northern China to study the occurrence and abundance of 21 ARGs and 2 integrase genes. Results indicated that 15 different ARGs and 2 integrase genes are existent and prevalent in the wastewater of OFM, whereby concentrations range from 2.01 to 10.34 copies/L. Proteobacteria, Bacteroidetes, Verrucomicrobia, and Firmicutes are the predominant phyla in the wastewater samples. 17 species of human opportunistic pathogens are present with relative abundance of up to 0.01%, which suggests a considerable risk of pathogens acquiring and disseminating ARGs. Moreover, oxytetracycline, ciprofloxacin, norfloxacin, sulfadiazine, and chloramphenicol are most frequently detected in wastewater, with concentrations of up to 1150, 877, 514, 1970, and 1700ng/L, respectively. Notably, good correlations have been determined among ARGs and antibiotics, non-antibiotic environmental factors in wastewater of OFM. This current study reveals, for the first time, that OFM is a previously unperceived reservoir for ARG prevalence in aquatic environment and water environmental factors (particularly antibiotics), and their induced shifts in the microbial communities are the key factors for distribution of ARGs in OFM.

Diverse and abundant resistome in terrestrial and aquatic vertebrates revealed by transcriptional analysis

Despite increasing evidence that antibiotic resistant pathogens are shared among humans and animals, the diversity, abundance and patterns of spread of antibiotic resistance genes (ARGs) in wildlife remains unclear. We identified 194 ARGs associated with phenotypic resistance to 13 types of antibiotic in meta-transcriptomic data generated from a broad range of lower vertebrates residing in both terrestrial and aquatic habitats. These ARGs, confirmed by PCR, included those that shared high sequence similarity to clinical isolates of public health concern. Notably, the lower vertebrate resistome varied by ecological niche of the host sampled. The resistomes in marine fish shared high similarity and were characterized by very high abundance, distinct from that observed in other habitats. An assessment of ARG mobility found that ARGs in marine fish were frequently co-localized with mobile elements, indicating that they were likely spread by horizontal gene transfer. Together, these data reveal the remarkable diversity and transcriptional levels of ARGs in lower vertebrates, and suggest that these wildlife species might play an important role in the global spread of ARGs.

The removal of moisture and antibiotic resistance genes in dairy manure by microwave treatment.

To characterize the drying of dairy manure during microwave (MW) heating, and to determine the impacts of microwave radiation on reductions of antibiotic resistance genes (ARGs), this study investigated on understanding the effects of microwave heating on solid streams of flushed dairy manure. A series of experiments were performed to determine the rate of drying, moisture removal percentages, change in solids, and the level of ARGs. Manure was exposed to microwave radiation for 30-300 s at a frequency of 2450 MHz. The results showed moisture removal rate (U) up to 0.63-g water per minute per gram of dairy manure. During MW treatment, volatile solid (VS) content was relatively stable. The MW treatment resulted in reduction of ARGs such as sulII, intI1, and tnpA. The ARG concentrations (sulII, intI1, and tnpA) were reduced by 2 orders of magnitude in less than 1 min of microwave heating. The preliminary results of this study showed that MW treatment can be a viable option for drying of dairy manure and reducing ARGs in manure.

A Microbiome-Based Solution to Address Alarming Levels of Drug-Resistant Bacteria in the Newborn Infant Gut

Background: Recent studies have focused on the early infant gut microbiome, indicating that antibiotic resistance genes (ARGs) can be acquired in early life and may have long-term sequelae. Limiting the spread of antimicrobial resistance without triggering the development of additional resistance mechanisms would be of immense clinical value. Here, we present 2 analyses that highlight the abundance of ARGs in preterm and term infants and a proof of concept for modulating the microbiome to promote early stabilization and reduction in ARGs in term infants. Methods: Large-scale metagenomic analysis was performed on 2,141 microbiome samples (90% from pre-term infants) from 10 countries; most were from the United States (87%) and were obtained from the Comprehensive Antibiotic Resistance Database (CARD). We assessed the abundance and specific types of ARGs present. In the second study, healthy, breastfed infants were fed B. infantis EVC001 for 3 weeks starting at postnatal day 7. Stool samples were collected at day 21 and were processed utilizing shotgun metagenomics. Selected antimicrobial-resistant bacterial species were isolated, sequenced, and tested for minimal inhibitory concentrations to clinically relevant antibiotics. Results: In the first study, globally, 417 distinct ARGs were identified. The most abundant gene among all samples was annotated as msrE, a plasmid gene known to confer resistance to macrolide-lincosamide-streptogramin B (MLSB) antibiotics. The remaining most-abundant ARGs were efflux-pump genes associated with multidrug resistance. No significant association in antimicrobial resistance was found when considering delivery mode or antibiotic treatment in the first month of life. In the second study, the EVC001-fed group showed a significant decrease (90%) in ARGs compared to controls (P < .0001). ARGs that differed significantly between groups were predicted to confer resistance to β-lactams, fluoroquinolones, or multiple drug classes. Minimal inhibitory concentration assays confirmed resistance phenotypes among isolates Notably, we found resistance to extended-spectrum β-lactamases among healthy, vaginally delivered breastfed infants who had never been exposed to antibiotics. Conclusions: In this study, we show that the term and preterm infant microbiome contains alarming levels of ARGs associated with clinically relevant antibiotics harbored by bacteria commonly responsible for nosocomial infections. Colonization of the breastfed infant gut by a single strain of B. longum subsp infantis had profound impacts on the fecal metagenome, including reduction in ARGs and reduction of potential pathogens. These findings highlight the importance of developing novel approaches to limit the spread of ARGs among clinically relevant bacteria and the relevance of an additional approach in the effort to solve AR globally.Funding: Evolve BioSystems provided Funding: for this study.Disclosures: Giorgio Casaburi reports salary from Evolve BioSystems.

Occurrence and distribution of antibiotic resistance genes in lakes and reservoirs from water-receiving area of Eastern Route of the South-to-North Water Diversion Project, Northern China

Abstract To characterize antibiotic resistance genes (ARGs) in surface waterbodies in Shandong Province, and to understand the occurrence, diversity and resistance mechanism of ARGs, nine aquatic ecosystems were selected and evaluated regarding occurrence of ARGs in the period from 2018 to 2019. Thirty-three types and 242 subtypes of ARGs were detected in the nine waterbodies with the most subtypes in Wohushan (242) and Jihongtan (235), and the fewest ARGs in Datun (213) and Mishan (221). Among the top nine ARG types, MacB, BcrA, CarA and TetW were the dominant ARGs in these samples. Four groups of the study sites were distinguished by cluster analysis, indicating different distribution characteristics of ARGs in these waterbodies, and regional differences in ARG contamination. Efflux pumps were the predominant resistance mechanism in all the waterbodies in terms of both subtype number (49.2%) and abundance (70.4%), followed by operon, antibiotic inactivation and others. Our findings provide comprehensive information to better understand the contamination level of ARGs on a local level as well as for global considerations, and may be practically helpful for the prevention and control of ARG pollution.

Hydrometeorological Influence on Antibiotic‐Resistance Genes (ARGs) and Bacterial Community at a Recreational Beach in Korea

We investigated the occurrence and distribution of antibiotic‐resistance genes (ARGs) and the composition of a bacterial community under conditions of rainfall on a recreational beach in Korea. Seawater samples, collected every 1‒5 hours in June 2018 and May 2019, were analyzed using quantitative real-time polymerase chain reaction and next-generation sequencing. We found a substantial influence of rainfall and tidal levels on the relative abundance of total ARGs and bacterial operational taxonomic units (OTUs), which showed 1.9 × 103 and 1.1 × 101 fold increases, respectively. In particular, the elevated levels of ARGs were maintained for up to 32 hours after rainfall. An increased abundance of sewage‐related ARGs and bacterial OTUs suggested that combined sewer overflow (CSO) may be the major factor contributing to the increase in the number and diversity of ARGs and related bacterial communities. Network analysis of ARGs and OTUs indicated that, at the genus level, Acinetobacter, Pseudomonas, and Prevotella were the main potential pathogens carrying the observed ARGs in the recreational seawater. Overall, these findings highlight the potential threat to public health on beaches, and indicate the requirement for more adequate monitoring, with greater efforts to mitigate the propagation of ARGs arising from CSOs.

Fecal Pollution Drives Antibiotic Resistance and Class 1 Integron Abundance in Aquatic Environments of the Bolivian Andes Impacted by Mining and Wastewater.

An increased abundance of antibiotic resistance genes (ARGs) in aquatic environments has been linked to environmental pollution. Mining polluted sites with high concentration of metals could favor the in situ coselection of ARGs, whereas wastewater discharges release fecal antibiotic resistant bacteria in the environment. To study the effect of human fecal contamination and mining pollution, water and sediment samples affected by mining activities and sewage discharges were collected from three lakes in Bolivia, the pristine Andean lake Pata Khota, the Milluni Chico lake directly impacted by acid mine drainage, and the Uru-Uru lake located close to Oruro city and highly polluted by mining activities and human wastewater discharges. Physicochemical parameters, including metal composition, were analyzed in water and sediment samples. ARGs were screened for and verified by quantitative polymerase chain reaction (PCR) together with the mobile element class 1 integron (intl1), as well as crAssphage, a marker of human fecal pollution. The gene intl1 was positively correlated with sul1, sul2, tetA, and blaOXA-2. CrAssphage was only detected in the Uru-Uru lake, and its tributaries and significantly higher abundance of ARGs were found in these sites. Multivariate analysis showed that crAssphage abundance, electrical conductivity, and pH were positively correlated with higher levels of intl1 and ARGs. Taken together, our results suggest that fecal pollution is the major driver of higher levels of ARGs and intl1 in environments contaminated by wastewater and mining activities.

High levels of antibiotic resistance genes and opportunistic pathogenic bacteria indicators in urban wild bird feces

This study analyzed fresh feces from three common bird species that live in urban environments and interact with human communities. Antibiotic resistance genes (ARGs) encoding resistance to three major classes of antibiotics (i.e., tetracyclines, β-lactams, and sulfonamides) and the mobile genetic element integrase gene (intI1) were abundant (up to 109, 108, 109, and 1010 copies/g dry feces for tetW, blaTEM, sul1, and intI1, respectively), with relative concentrations surprisingly comparable to that in poultry and livestock that are occasionally fed antibiotics. Biomarkers for opportunistic pathogens were also abundant (up to 107 copies/g dry feces) and the dominant isolates (i.e., Enterococcus spp. and Pseudomonas aeruginosa) harbored both ARGs and virulence genes. ARGs in bird feces followed first-order attenuation with half-lives ranging from 1.3 to 11.1 days in impacted soil. Although residual antibiotics were detected in the feces, no significant correlation was observed between fecal antibiotic concentrations and ARG relative abundance. Thus, other unaccounted factors likely contributed selective pressure for ARG maintenance. These findings highlight the contribution of wild urban bird feces to the maintenance and dissemination of ARGs, and the associated health risks.

Changes in Antibiotic Resistance Gene Levels in Soil after Irrigation with Treated Wastewater: A Comparison between Heterogeneous Photocatalysis and Chlorination.

Wastewater (WW) reuse is expected to be increasingly indispensable in future water management to mitigate water scarcity. However, this increases the risk of antibiotic resistance (AR) dissemination via irrigation. Herein, a conventional (chlorination) and an advanced oxidation process (heterogeneous photocatalysis (HPC)) were used to disinfect urban WW to the same target of Escherichia coli <10 CFU/100 mL and used to irrigate lettuce plants (Lactuca sativa) set up in four groups, each receiving one of four water types, secondary WW (positive control), fresh water (negative control), chlorinated WW, and HPC WW. Four genes were monitored in water and soil, 16S rRNA as an indicator of total bacterial load, intI1 as a gene commonly associated with anthropogenic activity and AR, and two AR genes blaOXA-10 and qnrS. Irrigation with secondary WW resulted in higher dry soil levels of intI1 (from 1.4 × 104 copies/g before irrigation to 3.3 × 105 copies/g after). HPC-treated wastewater showed higher copy numbers of intI1 in the irrigated soil than chlorination, but the opposite was true for blaOXA-10. The results indicate that the current treatment is insufficient to prevent dissemination of AR markers and that HPC does not offer a clear advantage over chlorination.

Antibiotic resistance in water environment: Frontiers of fundamental research, risk assessment and control strategies

<p indent=0mm>Antibiotic resistance has been considered as a major health security challenge of the 21st century in the 2013 G8 Science Minsters Statement. UN Environment ranked “Antimicrobial Resistance: Investigating the Environmental Dimension” as No.1 emerging issue among the six emerging issues of environmental concern in 2017. It should be pointed out that antibiotic resistance is not just a regional or national phenomenon but also a global problem, indicated by the famously typical cases of the rapid dissemination of <italic>Klebsiella pneumonia</italic> carbapenemase-positive bacteria and New Delhi metallo-β-lactamase-positive bacteria in Asia, Europe and North America. Animal waste, antibiotic production wastewater, hospital wastewater, sewage, sludge, soil, sediment, surface water and even air have been considered as important reservoirs for antibiotic resistance genes (ARGs) because abundant ARGs have been frequently detected in these environments. Among the different environment types, the water environment is a key node for the dissemination of antibiotic resistance. A large number of previous studies mainly focused on the abundance and diversity of ARGs in the water environments. However, the systematic and in-depth studies on the source, spread and fate of ARGs in the water environment are still limited. The basic framework and sophisticated models for risk assessment are still lacking for environments even possessing data of antibiotic concentration and exposure levels of ARGs. In addition, there is also no strategic thinking in the formulation and implementation of antibiotic resistance control strategies. Considering the above issues, this review will focus on the frontiers of fundamental research, risk assessment, and control strategies of antibiotic resistance in water environment and other environments, including: (1) The establishment of standardized detection approach and public database for antibiotics, i.e., the major selection pressure of antibiotic resistance; (2) the migration, transformation and bioavailability of antibiotics; (3) the transfer and dissemination of ARGs in the wastewater treatment plants; (4) exploring the standardized methods for investigating exposure levels of ARGs: metagenomic approach & high-throughput qPCR approach; (5) the key mobile genetic elements responsible for horizontal gene transfer and environmental transmission of ARGs; (6) deep mining and machine learning of ARGs using metagenomic/genomic big data. Several case studies were selected respectively to demonstrate current research status of the above six frontiers of fundamental research, risk assessment, and control strategies of antibiotic resistance. For the risk assessment, two types of risks including the risk of antibiotic treatment failure and the risk of ARGs dissemination in the environment should be distinguished. The prevention and control strategy of antibiotic resistance involves multi-disciplinary linkage and combination together, which requires the joint efforts of clinical medicine, ecology, agriculture, pharmacy, environmental science and engineering, as well as the cooperation of education, etc. Currently, following the integrative strategy of One Health, we should give the first priority to the investment on prevention and control measures at the key emission sources and other nodes to effectively reduce and ultimately stop the emissions of antibiotics and ARGs. The key emission sources mainly include antibiotic manufacturing factory, livestock farm, aquaculture farms, slaughter house, hospital and municipal wastewater treatment plants etc.

Deciphering the role of calcium peroxide on the fate of antibiotic resistance genes and mobile genetic elements during bioelectrochemically-assisted anaerobic composting of excess dewatered sludge

The integration of bioelectrochemical system (BES) into conventional anaerobic composting process can accelerate the degradation of excess dewatered sludge (ES). However, no reports have been made concerning antibiotic resistance genes (ARGs) profile and abundance in BESs fuelled with ES, and the effect of CaO2 on the fate of ARGs within BESs treating excess sludge has rarely been investigated. The aim of this study was to investigate the effect of CaO2 and the bioelectrochemical process on the abundances of ARGs and MGEs and to unravel the mechanism of ARGs attenuation. Results showed that CaO2 addition could enhance the reduction of ARG levels in ES within AnCBE. The mean ARG abundances in the AnCBE samples with high CaO2 doses (0.4 g CaO2/g VSS and 0.5 g CaO2/g VSS) were significantly lower than the values in samples with other CaO2 doses. The abundances of lincosamide nucleotidyltransferase, macB, macrolide transporter ATP-binding proteins, and macrolide-efflux proteins significantly decreased with the increase in the CaO2 dose. Both CaO2 addition and bioelectrochemical assistance played important roles in shaping the ARG composition during the AnCBE process. The variation in the microbial community composition is the most important contributor to the variation in the ARGs composition. The abundances of Actinobacteria and Firmicutes explained 52.8% of the total ARG variance. Of the MGEs, the abundances of plasmids, insertion sequences, and integrons were all reduced in the sludge metagenomes. There was a significantly positive correlation between the abundances of sulI, sulII, tetG, and blaTEM and those of metal resistance genes (MRGs), which decreased significantly after the AnCBE process. This study revealed the potential of the combination of CaO2 and bioelectrogenesis for ARG attenuation.