Modelling the impact of wastewater flows and management practices on antimicrobial resistance in dairy farms. - Related Documents




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656101.0000Modelling the impact of wastewater flows and management practices on antimicrobial resistance in dairy farms. Dairy slurry is a major source of environmental contamination with antimicrobial resistant genes and bacteria. We developed mathematical models and conducted on-farm research to explore the impact of wastewater flows and management practices on antimicrobial resistance (AMR) in slurry. Temporal fluctuations in cephalosporin-resistant Escherichia coli were observed and attributed to farm activities, specifically the disposal of spent copper and zinc footbath into the slurry system. Our model revealed that resistance should be more frequently observed with relevant determinants encoded chromosomally rather than on plasmids, which was supported by reanalysis of sequenced genomes from the farm. Additionally, lower resistance levels were predicted in conditions with lower growth and higher death rates. The use of muck heap effluent for washing dirty channels did not explain the fluctuations in cephalosporin resistance. These results highlight farm-specific opportunities to reduce AMR pollution, beyond antibiotic use reduction, including careful disposal or recycling of waste antimicrobial metals.202438757121
398010.9998Antimicrobial resistance in dairy slurry tanks: A critical point for measurement and control. Waste from dairy production is one of the largest sources of contamination from antimicrobial resistant bacteria (ARB) and genes (ARGs) in many parts of the world. However, studies to date do not provide necessary evidence to inform antimicrobial resistance (AMR) countermeasures. We undertook a detailed, interdisciplinary, longitudinal analysis of dairy slurry waste. The slurry contained a population of ARB and ARGs, with resistances to current, historical and never-used on-farm antibiotics; resistances were associated with Gram-negative and Gram-positive bacteria and mobile elements (ISEcp1, Tn916, Tn21-family transposons). Modelling and experimental work suggested that these populations are in dynamic equilibrium, with microbial death balanced by fresh input. Consequently, storing slurry without further waste input for at least 60 days was predicted to reduce ARB spread onto land, with > 99 % reduction in cephalosporin resistant Escherichia coli. The model also indicated that for farms with low antibiotic use, further reductions are unlikely to reduce AMR further. We conclude that the slurry tank is a critical point for measurement and control of AMR, and that actions to limit the spread of AMR from dairy waste should combine responsible antibiotic use, including low total quantity, avoidance of human critical antibiotics, and choosing antibiotics with shorter half-lives, coupled with appropriate slurry storage.202236122459
368320.9998Small and large-scale distribution of four classes of antibiotics in sediment: association with metals and antibiotic resistance genes. Antibiotic chemicals and antibiotic resistance genes enter the environment via wastewater effluents as well as from runoff from agricultural operations. The relative importance of these two sources, however, is largely unknown. The relationship between the concentrations of chemicals and genes requires exploration, for antibiotics in the environment may lead to development or retention of resistance genes by bacteria. The genes that confer resistance to metal toxicity may also be important in antibiotic resistance. In this work, concentrations of 19 antibiotics (using liquid chromatography tandem mass spectrometry), 14 metals (using inductively coupled plasma-mass spectrometry), and 45 metal, antibiotic, and antibiotic-resistance associated genes (using a multiplex, microfluidic quantitative polymerase chain reaction method) were measured in 13 sediment samples from two large rivers as well as along a spatial transect in a wastewater effluent-impacted lake. Nine of the antibiotics were detected in the rivers and 13 were detected in the lake. Sixteen different resistance genes were detected. The surrounding land use and proximity to wastewater treatment plants are important factors in the number and concentrations of antibiotics detected. Correlations among antibiotic chemical concentrations, metal concentrations, and resistance genes occur over short spatial scales in a lake but not over longer distances in major rivers. The observed correlations likely result from the chemicals and resistance genes arising from the same source, and differences in fate and transport over larger scales lead to loss of this relationship.201830043816
747430.9998Fecal pollution can explain antibiotic resistance gene abundances in anthropogenically impacted environments. Discharge of treated sewage leads to release of antibiotic resistant bacteria, resistance genes and antibiotic residues to the environment. However, it is unclear whether increased abundance of antibiotic resistance genes in sewage and sewage-impacted environments is due to on-site selection pressure by residual antibiotics, or is simply a result of fecal contamination with resistant bacteria. Here we analyze relative resistance gene abundance and accompanying extent of fecal pollution in publicly available metagenomic data, using crAssphage sequences as a marker of human fecal contamination (crAssphage is a bacteriophage that is exceptionally abundant in, and specific to, human feces). We find that the presence of resistance genes can largely be explained by fecal pollution, with no clear signs of selection in the environment, with the exception of environments polluted by very high levels of antibiotics from manufacturing, where selection is evident. Our results demonstrate the necessity to take into account fecal pollution levels to avoid making erroneous assumptions regarding environmental selection of antibiotic resistance.201930622259
740740.9998Impact of salmon farming in the antibiotic resistance and structure of marine bacterial communities from surface seawater of a northern Patagonian area of Chile. BACKGROUND: Aquaculture and salmon farming can cause environmental problems due to the pollution of the surrounding waters with nutrients, solid wastes and chemicals, such as antibiotics, which are used for disease control in the aquaculture facilities. Increasing antibiotic resistance in human-impacted environments, such as coastal waters with aquaculture activity, is linked to the widespread use of antibiotics, even at sub-lethal concentrations. In Chile, the world's second largest producer of salmon, aquaculture is considered the primary source of antibiotics residues in the coastal waters of northern Patagonia. Here, we evaluated whether the structure and diversity of marine bacterial community, the richness of antibiotic resistance bacteria and the frequency of antibiotic resistance genes increase in communities from the surface seawater of an area with salmon farming activities, in comparison with communities from an area without major anthropogenic disturbance. RESULTS: The taxonomic structure of bacterial community was significantly different between areas with and without aquaculture production. Growth of the culturable fraction under controlled laboratory conditions showed that, in comparison with the undisturbed area, the bacterial community from salmon farms displayed a higher frequency of colonies resistant to the antibiotics used by the salmon industry. A higher adaptation to antibiotics was revealed by a greater proportion of multi-resistant bacteria isolated from the surface seawater of the salmon farming area. Furthermore, metagenomics data revealed a significant higher abundance of antibiotic resistant genes conferring resistance to 11 antibiotic families in the community from salmon farms, indicating that the proportion of bacteria carrying the resistance determinants was overall higher in salmon farms than in the undisturbed site. CONCLUSIONS: Our results revealed an association between bacterial communities and antibiotic resistance from surface seawater of a coastal area of Chile. Although the total bacterial community may appear comparable between sites, the cultivation technique allowed to expose a higher prevalence of antibiotic resistant bacteria in the salmon farming area. Moreover, we demonstrated that metagenomics (culture-independent) and phenotypic (culture-dependent) methods are complementary to evaluate the bacterial communities' risk for antibiotic resistance, and that a human-influenced environment (such as salmon farms) can potentiate bacteria to adapt to environmental stresses, such as antibiotics.202439523335
738850.9998Poultry manure-derived microorganisms as a reservoir and source of antibiotic resistance genes transferred to soil autochthonous microorganisms. Animal husbandry is increasing yearly due to the growing demand for meat and livestock products, among other reasons. To meet these demands, prophylactic antibiotics are used in the livestock industry (i.e., poultry farming) to promote health and stimulate animal growth. However, antibiotics are not fully metabolized by animals, and they are evacuated to the environment with excreta. Animal manure is used as fertilizer to reduce the volume of waste generated in the livestock sector. However, manure often contains microorganisms harboring antibiotic resistance genes (ARGs). Then, the microbiome of manure applicate to the soil may contribute to the spread of antibiotic resistance in the environment, including autochthonous soil-dwelling microorganisms. The present study was conducted during the crops growing season in Poland (May to September 2019) to determine the influence of poultry manure as well as poultry manure supplemented with selected antibiotics on the diversity of the soil microbiome in treatments that had not been previously fertilized with manure and the ability of antibiotic-resistant bacteria to transfer ARGs to other soil bacteria. Antibiotic concentrations were elevated at the beginning of the study and decreased over time. Poultry manure induced significant changes in the structure of microbial communities in soil; the diversity of the soil microbiome decreased, and the abundance of bacterial genera Bradyrhizobium, Streptomyces, and Pseudomonas, which are characteristic of the analyzed manure, increased. Over time, soil microbial diversity was restored to the state observed before the application of manure. Genes conferring resistance to multiple drugs as well as genes encoding resistance to bacitracin and aminoglycosides were the most frequently identified ARGs in the analyzed bacteria, including on mobile genetic elements. Multidrug resistance was observed in 17 bacterial taxa, whereas ARGs were identified in 32 bacterial taxa identified in the soil microbiome. The results of the study conclude that the application of poultry manure supplemented with antibiotics initially affects soil microbiome and resistome diversity but finally, the soil shows resilience and returns to its original state after time, with most antibiotic resistance genes disappearing. This phenomenon is of great importance in sustainable soil health after manure application.202337832303
740660.9998Relationship between antibiotic resistance genes and metals in residential soil samples from Western Australia. Increasing drug-resistant infections have drawn research interest towards examining environmental bacteria and the discovery that many factors, including elevated metal conditions, contribute to proliferation of antibiotic resistance (AR). This study examined 90 garden soils from Western Australia to evaluate predictions of antibiotic resistance genes from total metal conditions by comparing the concentrations of 12 metals and 13 genes related to tetracycline, beta-lactam and sulphonamide resistance. Relationships existed between metals and genes, but trends varied. All metals, except Se and Co, were related to at least one AR gene in terms of absolute gene numbers, but only Al, Mn and Pb were associated with a higher percentage of soil bacteria exhibiting resistance, which is a possible indicator of population selection. Correlations improved when multiple factors were considered simultaneously in a multiple linear regression model, suggesting the possibility of additive effects occurring. Soil-metal concentrations must be considered when determining risks of AR in the environment and the proliferation of resistance.201727822686
739770.9998Persistence of naturally occurring antibiotic resistance genes in the bacteria and bacteriophage fractions of wastewater. The emergence and prevalence of antibiotic resistance genes (ARGs) in the environment is a serious global health concern. ARGs from bacteria can be mobilized by mobile genetic elements, and recent studies indicate that phages and phage-derived particles, among others, could play a role in the spread of ARGs through the environment. ARGs are abundant in the bacterial and bacteriophage fractions of water bodies and for successful transfer of the ARGs, their persistence in these environments is crucial. In this study, three ARGs (blaTEM, blaCTX-M and sul1) that naturally occur in the bacterial and phage fractions of raw wastewater were used to evaluate the persistence of ARGs at different temperatures (4 °C, 22 °C and 37 °C) and pH values (3, 7 and 9), as well as after various disinfection treatments (thermal treatment, chlorination and UV) and natural inactivation in a mesocosm. Gene copies (GC) were quantified by qPCR; then the logarithmic reduction and significance of the differences between their numbers were evaluated. The ARGs persisted for a long time with minimal reductions after all the treatments. In general, they showed greater persistence in the bacteriophage fraction than in the bacterial fraction. Comparisons showed that the ARGs persisted under conditions that reduced culturable Escherichia coli and infectious coliphages below the limit of detection. The prevalence of ARGs, particularly in the bacteriophage fraction, poses the threat of the spread of ARGs and their incorporation into a new bacterial background that could lead to the emergence of new resistant clones.201626978717
739380.9998Fate and distribution of determinants of antimicrobial resistance in lateral flow sand filters used for treatment of domestic wastewater. Residuals of antimicrobial products from anthropogenic uses can create a selective environment in domestic wastewater treatment systems and receiving environments and contribute to the spread of antimicrobial resistance (AMR). On-site wastewater treatment systems are widely used for domestic wastewater management in rural and remote regions, but the fate of determinants of AMR in these types of environments has received little attention. In this study, the mechanisms responsible for the attenuation of determinants of AMR in lateral flow sand filters were explored using a combination of lab, field and modeling investigations. The degradation kinetics and adsorption potential in the sand filter medium of three antibiotic resistance genes (ARGs; sul1, tetO, and ermB) and culturable bacteria resistant to sulfamethoxazole, tetracycline, and erythromycin were measured using lab experiments. The spatial distribution of ARGs and antibiotic resistant bacteria were also assessed in field scale sand filters, and mechanistic modeling was conducted to characterize filtration processes. The results indicated that the primary mechanisms responsible for AMR attenuation within the sand filters were degradation and filtration. The spatial distribution of AMR determinants illustrated that attenuation was occurring along the entire length of each filter. This study provides new insights on primary mechanisms of AMR attenuation in on-site wastewater treatment systems and supports the use of conservative design guidelines and separation distances for reducing AMR transmission.202133636762
385990.9998Co-selection of antibiotic resistance via copper shock loading on bacteria from a drinking water bio-filter. Heavy metal contamination of source water frequently occurred in developing countries as a result of accidents. To address the problems, most of the previous studies have focused on engineering countermeasures. In this study, we investigated the effects of heavy metals, particularly copper, on the development of antibiotic resistance by establishing a copper shock loading test. Results revealed that co-selection occurred rapidly within 6 h. Copper, at the levels of 10 and 100 mg/L, significantly increased bacterial resistance to the antibiotics tested, including rifampin, erythromycin, kanamycin, and a few others. A total of 117 antimicrobial-resistance genes were detected from 12 types of genes, and the relative abundance of most genes (particularly mobile genetic elements intⅠand transposons) was markedly enriched by at least one fold. Furthermore, the copper shock loading altered the bacterial community. Numerous heavy metal and antibiotic resistant strains were screened out and enriched. These strains are expected to enhance the overall level of resistance. More noticeably, the majority of the co-selected antibiotic resistance could sustain for at least 20 h in the absence of copper and antimicrobial drugs. Resistance to vancomycin, erythromycin and lincomycin even could remain for 7 days. The prominent selection pressure by the copper shock loading implies that a real accident most likely poses similar impacts on the water environment. An accidental release of heavy metals would not only cause harm to the ecological environment, but also contribute to the development of bacterial antibiotic resistance. Broader concerns should be raised about the biological risks caused by sudden releases of pollutants by accidents.201829059628
7429100.9998Industrial wastewater treatment plant enriches antibiotic resistance genes and alters the structure of microbial communities. Antibiotic resistance is an emerging global health crisis, driven largely by overuse and misuse of antibiotics. However, there are examples in which the production of these antimicrobial agents has polluted the environment with active antibiotic residues, selecting for antibiotic resistant bacteria and the genes they carry. In this work, we have used shotgun metagenomics to investigate the taxonomic structure and resistance gene composition of sludge communities in a treatment plant in Croatia receiving wastewater from production of the macrolide antibiotic azithromycin. We found that the total abundance of antibiotic resistance genes was three times higher in sludge from the treatment plant receiving wastewater from pharmaceutical production than in municipal sludge from a sewage treatment plant in Zagreb. Surprisingly, macrolide resistance genes did not have higher abundances in the industrial sludge, but genes associated with mobile genetic elements such as integrons had. We conclude that at high concentrations of antibiotics, selection may favor taxonomic shifts towards intrinsically resistant species or strains harboring chromosomal resistance mutations rather than acquisition of mobile resistance determinants. Our results underscore the need for regulatory action also within Europe to avoid release of antibiotics into the environment.201931301473
7395110.9998Impacts of anthropogenic activity on the ecology of class 1 integrons and integron-associated genes in the environment. The impact of human activity on the selection for antibiotic resistance in the environment is largely unknown, although considerable amounts of antibiotics are introduced through domestic wastewater and farm animal waste. Selection for resistance may occur by exposure to antibiotic residues or by co-selection for mobile genetic elements (MGEs) which carry genes of varying activity. Class 1 integrons are genetic elements that carry antibiotic and quaternary ammonium compound (QAC) resistance genes that confer resistance to detergents and biocides. This study aimed to investigate the prevalence and diversity of class 1 integron and integron-associated QAC resistance genes in bacteria associated with industrial waste, sewage sludge and pig slurry. We show that prevalence of class 1 integrons is higher in bacteria exposed to detergents and/or antibiotic residues, specifically in sewage sludge and pig slurry compared with agricultural soils to which these waste products are amended. We also show that QAC resistance genes are more prevalent in the presence of detergents. Studies of class 1 integron prevalence in sewage sludge amended soil showed measurable differences compared with controls. Insertion sequence elements were discovered in integrons from QAC contaminated sediment, acting as powerful promoters likely to upregulate cassette gene expression. On the basis of this data, >1 × 10(19) bacteria carrying class 1 integrons enter the United Kingdom environment by disposal of sewage sludge each year.201121368907
7701120.9997Elucidating selection processes for antibiotic resistance in sewage treatment plants using metagenomics. Sewage treatment plants (STPs) have repeatedly been suggested as "hotspots" for the emergence and dissemination of antibiotic-resistant bacteria. A critical question still unanswered is if selection pressures within STPs, caused by residual antibiotics or other co-selective agents, are sufficient to specifically promote resistance. To address this, we employed shotgun metagenomic sequencing of samples from different steps of the treatment process in three Swedish STPs. In parallel, concentrations of selected antibiotics, biocides and metals were analyzed. We found that concentrations of tetracycline and ciprofloxacin in the influent were above predicted concentrations for resistance selection, however, there was no consistent enrichment of resistance genes to any particular class of antibiotics in the STPs, neither for biocide and metal resistance genes. The most substantial change of the bacterial communities compared to human feces occurred already in the sewage pipes, manifested by a strong shift from obligate to facultative anaerobes. Through the treatment process, resistance genes against antibiotics, biocides and metals were not reduced to the same extent as fecal bacteria. The OXA-48 gene was consistently enriched in surplus and digested sludge. We find this worrying as OXA-48, still rare in Swedish clinical isolates, provides resistance to carbapenems, one of our most critically important classes of antibiotics. Taken together, metagenomics analyses did not provide clear support for specific antibiotic resistance selection. However, stronger selective forces affecting gross taxonomic composition, and with that resistance gene abundances, limit interpretability. Comprehensive analyses of resistant/non-resistant strains within relevant species are therefore warranted.201627542633
7405130.9997Microbial Diversity and Antimicrobial Resistance Profile in Microbiota From Soils of Conventional and Organic Farming Systems. Soil is one of the biggest reservoirs of microbial diversity, yet the processes that define the community dynamics are not fully understood. Apart from soil management being vital for agricultural purposes, it is also considered a favorable environment for the evolution and development of antimicrobial resistance, which is due to its high complexity and ongoing competition between the microorganisms. Different approaches to agricultural production might have specific outcomes for soil microbial community composition and antibiotic resistance phenotype. Therefore in this study we aimed to compare the soil microbiota and its resistome in conventional and organic farming systems that are continually influenced by the different treatment (inorganic fertilizers and pesticides vs. organic manure and no chemical pest management). The comparison of the soil microbial communities revealed no major differences among the main phyla of bacteria between the two farming styles with similar soil structure and pH. Only small differences between the lower taxa could be observed indicating that the soil community is stable, with minor shifts in composition being able to handle the different styles of treatment and fertilization. It is still unclear what level of intensity can change microbial composition but current conventional farming in Central Europe demonstrates acceptable level of intensity for soil bacterial communities. When the resistome of the soils was assessed by screening the total soil DNA for clinically relevant and soil-derived antibiotic resistance genes, a low variety of resistance determinants was detected (resistance to β-lactams, aminoglycosides, tetracycline, erythromycin, and rifampicin) with no clear preference for the soil farming type. The same soil samples were also used to isolate antibiotic resistant cultivable bacteria, which were predominated by highly resistant isolates of Pseudomonas, Stenotrophomonas, Sphingobacterium and Chryseobacterium genera. The resistance of these isolates was largely dependent on the efflux mechanisms, the soil Pseudomonas spp. relying mostly on RND, while Stenotrophomonas spp. and Chryseobacterium spp. on RND and ABC transporters.201931105678
7364140.9997Anthropogenic influence shapes the distribution of antibiotic resistant bacteria (ARB) in the sediment of Sundarban estuary in India. The abundance and dissemination of antibiotic resistance genes as emerging environmental contaminants have become a significant and growing threat to human and environmental health. Traditionally, investigations of antibiotic resistance have been confined to a subset of clinically relevant antibiotic-resistant bacterial pathogens. During the last decade it became evident that the environmental microbiota possesses an enormous number and diversity of antibiotic resistance genes, some of which are very similar to the genes circulating in pathogenic microbiota. Recent studies demonstrate that aquatic ecosystems are potential reservoirs of antibiotic-resistant bacteria (ARBs) and antibiotic resistance genes (ARGs). Therefore, these aquatic ecosystems serve as potential sources for their transmission of ARGs to human pathogens. An assessment of such risks requires a better understanding of the level and variability of the natural resistance background and the extent of the anthropogenic impact. We have analyzed eight sediment samples from Sundarban mangrove ecosystem in India, collected at sampling stations with different histories of anthropogenic influences, and analyzed the relative abundance of the bla(TEM) gene using quantitative real-time PCR. The bla(TEM) gene abundance strongly correlated with the respective anthropogenic influences (polyaromatic hydrocarbon, heavy metals etc.) of the sampling stations. Besides, 18 multidrug-resistant (ampicillin, kanamycin, vancomycin, and tetracycline resistant) bacterial strains (ARBs) were isolated and characterized. Moreover, the effect of different antibiotics on the biofilm forming ability of the isolates was evaluated quantitatively under a variety of experimental regimes. This is the first report of preservation and possible dissemination of ARGs in the mangrove ecosystem.201930180366
7409150.9997Longitudinal screening of antibiotic residues, antibiotic resistance genes and zoonotic bacteria in soils fertilized with pig manure. Fertilization with animal manure is one of the main routes responsible for the introduction of antibiotic residues, antibiotic resistance genes, and zoonotic bacteria into the environment. The aim of this study was to assess the effect of the use of pig (swine) manure as a fertilizer on the presence and fate of six antibiotic residues, nine antibiotic resistance genes, and bacteria (zoonotic bacteria Salmonella spp. and Campylobacter spp. and E. coli as indicator for Gram-negative bacterial species of the microbiota of livestock) on five fields. To the best of our knowledge, the present study is the first to assess a multitude of antibiotic residues and resistance to several classes of antibiotics in pig manure and in fertilized soil over time in a region with an intensive pig industry (Flanders, Belgium). The fields were sampled at five consecutive time points, starting before fertilization up to harvest. Low concentrations of antibiotic residues could be observed in the soils until harvest. The antibiotic resistance genes studied were already present at background levels in the soil environment prior to fertilization, but after fertilization with pig manure, an increase in relative abundance was observed for most of them, followed by a decline back to background levels by harvest-time on all of the fields studied. No apparent differences regarding the presence of antibiotic resistance genes in soils were observed between those fertilized with manure that either contained antibiotic residues or not. With regard to dissemination of resistance, the results presented in this study confirm that fertilization with animal manure directly adds resistance genes to the soil. In addition, it shows that this direct mechanism may be more important than possible selective pressure in soil-dwelling bacteria exerted by antibiotic residues present in the manure. These results also indicate that zoonotic bacteria detected in the manure could be detected in the soil environment directly after fertilization, but not after 1 month. In conclusion, although some antibiotic residues may be present in both manure and soil at concentrations to exert selective pressure, it seems that antibiotic resistance is mostly introduced directly to soil through fertilization with animal manure.202032410188
7396160.9997Antibiotic resistant bacteria and resistance genes in the bottom sediment of a small stream and the potential impact of remobilization. River sediments are regarded as hot spots of bacterial density and activity. Moreover, high bacterial densities and biofilm formation are known to promote horizontal gene transfer, the latter playing a vital role in the spread of antimicrobial resistance. It can thus be hypothesized that sediments act as a reservoir of antibiotic resistant bacteria (ARB) and resistance genes (ARGs), particularly in rivers receiving microbes and drug residues from treated sewage. We analyzed the phenotypic susceptibility of 782 Escherichia coli isolates against 24 antimicrobials and we measured the relative abundances of five ARGs in water and sediment extracts of a small stream. We did not find evidence for a general increase in the proportion of resistant E. coli isolated from sediments as compared to those found in stream water. For most antimicrobials, the likelihood of detecting a resistant isolate was similar in water and sediment or it was even lower in the latter compartment. The mean relative abundance of ARGs was moderately increased in sediment-borne samples. Generally, absolute abundances of resistant cells and resistance genes in the sediment exceeded the pelagic level owing to higher bacterial densities. The river bottom thus represents a reservoir of ARB and ARGs that can be mobilized by resuspension.201829982428
3979170.9997Mathematical modelling of antimicrobial resistance in agricultural waste highlights importance of gene transfer rate. Antimicrobial resistance is of global concern. Most antimicrobial use is in agriculture; manures and slurry are especially important because they contain a mix of bacteria, including potential pathogens, antimicrobial resistance genes and antimicrobials. In many countries, manures and slurry are stored, especially over winter, before spreading onto fields as organic fertilizer. Thus, these are a potential location for gene exchange and selection for resistance. We develop and analyse a mathematical model to quantify the spread of antimicrobial resistance in stored agricultural waste. We use parameters from a slurry tank on a UK dairy farm as an exemplar. We show that the spread of resistance depends in a subtle way on the rates of gene transfer and antibiotic inflow. If the gene transfer rate is high, then its reduction controls resistance, while cutting antibiotic inflow has little impact. If the gene transfer rate is low, then reducing antibiotic inflow controls resistance. Reducing length of storage can also control spread of resistance. Bacterial growth rate, fitness costs of carrying antimicrobial resistance and proportion of resistant bacteria in animal faeces have little impact on spread of resistance. Therefore, effective treatment strategies depend critically on knowledge of gene transfer rates.201626906100
7386180.9997Regulation of Antibiotic Resistance Genes on Agricultural Land Is Dependent on Both Choice of Organic Amendment and Prevalence of Predatory Bacteria. Antibiotic resistance genes (ARGs) are widespread in the environment, and soils, specifically, are hotspots for microorganisms with inherent antibiotic resistance. Manure and sludge used as fertilizers in agricultural production have been shown to contain vast amounts of ARGs, and due to continued applications, ARGs accumulate in agricultural soils. Some soils, however, harbor a resilience capacity that could depend on specific soil properties, as well as the presence of predatory bacteria that are able to hydrolyse living bacteria, including bacteria of clinical importance. The objectives of this study were to (i) investigate if the antibiotic resistance profile of the soil microbiota could be differently affected by the addition of cow manure, chicken manure, and sludge, and (ii) investigate if the amendments had an effect on the presence of predatory bacteria. The three organic amendments were mixed separately with a field soil, divided into pots, and incubated in a greenhouse for 28 days. Droplet digital PCR (ddPCR) was used to quantify three ARGs, two predatory bacteria, and total number of bacteria. In this study, we demonstrated that the choice of organic amendment significantly affected the antibiotic resistance profile of soil, and promoted the growth of predatory bacteria, while the total number of bacteria was unaffected.202439200050
3680190.9997Metagenomic Insights Into the Contribution of Phages to Antibiotic Resistance in Water Samples Related to Swine Feedlot Wastewater Treatment. In this study, we examined the types of antibiotic resistance genes (ARGs) possessed by bacteria and bacteriophages in swine feedlot wastewater before and after treatment using a metagenomics approach. We found that the relative abundance of ARGs in bacterial DNA in all water samples was significantly higher than that in phages DNA (>10.6-fold), and wastewater treatment did not significantly change the relative abundance of bacterial- or phage-associated ARGs. We further detected the distribution and diversity of the different types of ARGs according to the class of antibiotics to which they confer resistance, the tetracycline resistance genes were the most abundant resistance genes and phages were more likely to harbor ATP-binding cassette transporter family and ribosomal protection genes. Moreover, the colistin resistance gene mcr-1 was also detected in the phage population. When assessing the contribution of phages in spreading different groups of ARGs, β-lactamase resistance genes had a relatively high spreading ability even though the abundance was low. These findings possibly indicated that phages not only could serve as important reservoir of ARG but also carry particular ARGs in swine feedlot wastewater, and this phenomenon is independent of the environment.201830459724