Presence of erm genes among macrolide-resistant Gram-positive bacteria isolated from Danish farm soil

The presence of erm genes was investigated among macrolide-resistant Gram-positive bacteria isolated from soil samples collected from four Danish farms that had been treated with animal waste. Soil samples were collected before, a few days after spread and 1 1/2 months and 5 months later. In 33% (9/27) of these isolates, an erm gene was detected using PCR. Eight isolates were positive for erm(B) and one isolate was positive for erm(C). No isolates contained erm(A), erm(D) or erm(F). The positive isolates were identified to genus level. Two erm(B) positive isolates were identified as Enterococcus spp., and the erm(C)-positive isolate as a Streptococcus spp., probably indicating survival from animal waste. The remaining six erm(B) positive isolates all belonged to the Bacillus cereus group. The erm(B) gene has not previously been identified in B. cereus but is frequently found among enterococci. This result could indicate horizontal transfer from bacteria of animal origin to indigenous soil bacteria.     

Bacterial antibiotic resistance levels in Danish farmland as a result of treatment with pig manure slurry

Resistance to tetracycline, macrolides and streptomycin was measured for a period of 8 months in soil bacteria obtained from farmland treated with pig manure slurry. This was done by spread plating bacteria on selective media (Luria Bertani (LB) medium supplemented with antibiotics). To account for seasonal variations in numbers of soil bacteria, ratios of resistant bacteria divided by total count on nonselective plates were calculated. Soil samples were collected from four different farms and from a control soil on a fifth farm. The control soil was not amended with animal manure. The occurrence of tetracycline-resistant bacteria was elevated after spread of pig manure slurry but declined throughout the sampling period to a level corresponding to the control soil. Higher load of pig manure slurry yielded higher occurrence of tetracycline resistance after spreading; however, the tetracycline resistance declined to normal occurrence defined by the tetracycline resistance occurrence in the control soil. Concentrations of tetracycline in soil and in pig manure slurry were measured using HPLC. No tetracycline exceeding the detection limit was found in soil samples. Manure slurry concentrations of tetracycline for three of the farms were 42, 81 and 698 microg/l, respectively. For streptomycin and macrolides, only minor variations in resistance levels were detected. Results obtained in this study thus indicate that tetracycline resistance levels in soil are temporarily influenced by the addition of pig manure slurry. The results indicate also that increased amount of pig manure slurry amendment may result in increased levels of tetracycline resistance in the soil.     

Development of a rapid method for direct detection of tet(M) genes in soil from Danish farmland

A method for direct detection of antibiotic resistance genes in soil samples has been developed. The tetracycline resistance gene, tet(M), was used as a model. The method was validated on Danish farmland soil that had repeatedly been treated with pig manure slurry containing resistant bacteria. The tet(M) gene was directly detected in 10-80% of the samples from the various farmland soils and could be detected in all samples tested after selective enrichment. To validate the obtained results, the method was applied to garden soil samples where lower prevalence of resistance was found. RESULT: A detection limit of 10(2)-10(3) copies of the tet(M) gene per gram of soil (in a Bacillus cereus group bacterium) was achieved. tet(M) gene was detected in soil samples with the highest prevalence on farmland treated with pig manure slurry.     

基于效果-效率-适应性的养殖废弃物资源化利用管理模式评价框架构建及初步应用

由于产业发展正处于转型阶段,我国畜禽养殖污染治理中的管理问题比技术问题更加突出,选择适宜的组织管理模式尤其重要。融合了效果分析、效率评价和适应性分析,尝试构建一个养殖废弃物资源化利用管理模式综合评价框架,并选择太湖流域4个不同类型的典型案例进行方法例证。研究表明,传统的养殖企业主导型管理模式应用于小型、分散养殖废弃物资源化利用时面临着经济效率低、适应性差难题;农村废弃物处理中心、种植企业和有机肥企业的参与可以改善小型、分散养殖废弃物资源化利用的经济效率;综合考虑效果、效率与适应性,种植企业、有机肥企业主导型模式的适宜推广范围更广。应根据不同地区种植-养殖产业关系、污染治理需求、经济发展水平与政府投入能力等,灵活组合应用不同管理模式。     

Characterisation, dissemination and persistence of gentamicin resistant Escherichia coli from a Danish university hospital to the waste water environment

The aim of the study was to investigate the potential spread of gentamicin resistant (GEN(R)) Escherichia coli isolates or GEN(R) determinants from a Danish university hospital to the waste water environment. Waste water samples were collected monthly from the outlets of the hospital bed wards and the inlet of the related waste water treatment plant (WWTP) from October 2002 to August 2003. Waste water samples were also collected monthly from a residential area in the same period to be able to compare the prevalence of GEN(R)E. coli isolates from hospital related and residential waste water. The waste water isolates were compared to GEN(R)E. coli isolates obtained consecutively from September 2002 to September 2003 from patients mainly with urinary tract infections at the hospital with respect to Pulsed Field Gel Electrophoresis (PFGE) profiles. All isolates were investigated for GEN(R) mechanisms (aac(3)-II, aac(3)-IV, ant(2')-I, armA), phenotypic resistance pattern, and virulence genes (hlyA, chuA, sfaS, fogG, malX, traT, iutA, fyuA, iroN, cnf1) to investigate if the hospital and waste water could be reservoirs of antimicrobial resistance and virulence. The ability for GEN(R) determinants to transfer horizontally was investigated by mating experiments. A total of 38, 15, 21, and two GEN(R)E. coli were isolated from patients, the hospital outlets, the inlet of the WWTP, and the residential area, respectively. GEN(R)E. coli were more prevalent in waste water from the hospital and the WWTP than in waste water from the residential area. PFGE profiling revealed no spread of specific patient isolates to the waste water. The aac(3)-II gene was detected both in patient and waste water isolates. Furthermore horizontal transfer of the aac(3)-II gene of patient origin to a recipient was shown in vitro, indicating a potential spread of the gene from patient isolates to waste water isolates. Regardless of origin, most isolates exhibited multi-resistance and contained several virulence genes. In conclusion, our study showed a possible spread of aac(3)-II from the hospital to the waste water. Most of the GEN(R)E. coli isolates from both patients and waste water had a multi-resistant phenotype and contained virulence genes and should therefore be considered reservoirs of antimicrobial resistance and virulence genes.     

Discharge of swine wastes risks water quality and food safety: Antibiotics and antibiotic resistance genes from swine sources to the receiving environments

Swine feedlots are widely considered as a potential hotspot for promoting the dissemination of antibiotic resistance genes (ARGs) in the environment. ARGs could enter the environment via discharge of animal wastes, thus resulting in contamination of soil, water, and food. We investigated the dissemination and diversification of 22 ARGs conferring resistance to sulfonamides, tetracyclines, chloramphenicols, and macrolides as well as the occurrence of 18 corresponding antibiotics from three swine feedlots to the receiving water, soil environments and vegetables. Most ARGs and antibiotics survived the on-farm waste treatment processes in the three swine farms. Elevated diversity of ARGs was observed in the receiving environments including river water and vegetable field soils when compared with respective controls. The variation of ARGs along the vertical soil profiles of vegetable fields indicated enrichment and migration of ARGs. Detection of various ARGs and antibiotic residues in vegetables fertilized by swine wastes could be of great concern to the general public. This research demonstrated the contribution of swine wastes to the occurrence and development of antibiotic resistance determinants in the receiving environments and potential risks to food safety and human health.     

How do soil and water conservation practices influence climate change impacts on potato production? Evidence from eastern Canada

We used a stochastic production function method together with a farm-level dataset covering 18 farms over a 23-year period to assess the role that soil and water conservation practices play in affecting the climate change impacts on potato yield in northwestern New Brunswick, Canada. Our analysis accounted for the yield effects of farm inputs, farm technologies, farm-specific factors, seasonal climatic variables, soil and water conservation practices, and a series of interaction terms between soil and water conservation practices and climatic variables. Regression results were used in combination with three climate change scenarios developed by the Intergovernmental Panel on Climate Change (A2, A1B, B1) and four general circulation model predictions over three 30-year time periods (2011–2040, 2041–2070, and 2071–2100) to estimate a range of potato yield projections over these time periods. Results show that accounting for soil and water conservation practices in climate–yield relationships increased the impacts of climate change on potato yield, with yield increases of up to 38 % by the 2071–2100 period. These findings provide evidence that adoption of soil and water conservation practices can help boost potato production in a changing Canadian climate.     

Naphthalene biodegradation kinetics in an aerobic slurry-phase bioreactor

The research was focused on the slurry-phase biodegradation of naphthalene in soil. Among ex situ techniques, the slurry phase offers the advantage of increased availability of contaminants to bacteria. From naphthalene contaminated soil, a Pseudomonas putida M8 strain capable to degrade naphthalene was selected. Experiments were performed in a stirred and oxygenated reactor. In this study, the influence of air flow rate and agitation rate on volatilisation and biodegradation of naphthalene was investigated. The hydrocarbon disappearance, the carbon dioxide production, and the ratio of total heterotrophic and naphthalene-degrading bacteria was monitored. The results obtained confirm that the selected bioremediation technology is successful in the treatment of contaminated soils.     

A simplified method for the design and sizing of anaerobic digestion systems for smaller farms

Anaerobic digestion (AD) as a waste treatment practice has existed for nearly 200 years and has become an accepted option for many farming and small-scale residential operations. Many developing countries now encourage the use of AD in order to meet new environmental regulations and/or to provide small amounts of energy resulting from methane generated during the process. This development has been met with some difficulty due to the lack of resources and knowledge of the systems in many of the rural communities in which these digesters are placed. A properly designed AD system can help prevent soil and water pollution as well as help mitigate methane emissions by capturing them for use as a potential energy source. This paper focuses on providing guidance to the proper design and sizing of an AD system for typical small farms, which account for the majority of dairy farms worldwide. A focus was on the implementation of such systems as they might be applied in Central America, although the aspects studied here can be applied for AD systems handling animal waste streams practically anywhere. We provide a method for sizing of anaerobic digester systems based on design standards from the US National Resource Conservation Service and using field sampled data of holding pen wash water runoff. An overview of the decision process for alternative designs is given, and simple-to-use nomographs are presented for use in sizing of an anaerobic digester system for smaller (non-industrial)-scale farms.     

Extractable soil nutrient effects on feed quality traits of crop residues in the semiarid rainfed mixed crop–livestock farming systems of Southern India

In the mixed crop–livestock systems, while general relation among feed quality, productivity and soil nutrient management have been reported, information on the effects of extractable soil nutrients on crop residue (CR) feed quality traits is scarce (e.g. in semiarid regions of Karnataka, India). In view of the increasingly important role of CR as feed components, in these farming systems, generating such information is a relevant research issue for sustainable development. Here, we report the occurrence and strength of relationships among extractable nutrients in soils and CR feed quality traits, and the effects of improved nutrients input on feed availability and feed quality of CR. Soil samples were collected from farmers’ fields in the semiarid zone of Karnataka and analyzed for available phosphorus (P), potassium (K), sulphur (S), zinc (Zn) and boron (B) using standard laboratory methods. Soil test results were clustered as low, medium or high based on the level of nutrient concentration. Four major farming systems involving nine crops and 419 farms were selected for on-farm trials. Under every sample farm, a plot with farmer’s practice (control) and improved fertilizer inputs (combined application of nutrients found deficient by soil testing) were laid. Performance of crops was recorded. Samples were collected for CR feed quality trait analysis using Near Infrared Reflectance Spectroscopy. The result showed that for cereal and oil crops, extractable soil S was significantly negatively associated with anti-feed quality traits such as neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) (P < 0.01), but significantly positively related to metabolizable energy (ME) and in vitro digestibility (P < 0.01). Extractable B and K levels were associated positively and significantly with NDF, ADF and ADL for oil crops and cereals. Crop level associations, for most crops, showed similar trend. Improved fertilizer inputs affected CR yield much more than it did the quality. It increased ME productivity (ME ha^?1) and thereof the potential milk yield ha^?1 by as high as 40 % over the control. Therefore, balanced nutrient inputs on crop land positively impact productivity of the livestock compartment of mixed crop–livestock farming system, and this knowledge can build on the currently perceived need and benefits of balanced nutrient replenishment in crop–livestock system.     

Longer-duration uses of tetracyclines and penicillins in U.S. food-producing animals: Indications and microbiologic effects

We review and analyze regulatory categories for longer duration of use (defined as ≥ 7 day) tetracyclines (TCs) and penicillins (PNs) approved for U.S. livestock and poultry, together with scientific studies, surveillance programs and risk assessments pertaining to antimicrobial resistance. Indications listed on a government database were grouped into three broad categories according to the terminology used to describe their use: disease control (C), treatment (T) and growth improvement (G). Consistent with mostly therapeutic uses, the majority (86%) of listed indications had C and/or T terms. Several studies showed interruption of early disease stages in animals and modulation of intestinal microflora. Longer-duration exposures are consistent with bacteriostatic modes of action, where adequate exposure time as well as concentration is needed for sufficient antimicrobial activity. Other effects identified included reduced animal pathogen prevalence, toxin formation, inflammation, environmental impacts, improved animal health, reproductive measures, nutrient utilization, and others. Several animal studies have shown a limited, dose-proportionate, selective increase in resistance prevalence among commensal animal bacteria following longer-duration exposures. Pathogen surveillance programs showed overall stable or declining resistance trends among sentinel bacteria. Quantitative, microbiologically detailed resistance risk assessments indicate small probabilities of human treatment failure due to resistance under current conditions. Evaluations of longer-duration uses of TCs, PNs, and other antimicrobial classes used in food-producing animals should consider mechanisms of activity, known individual- and population-level health and waste reduction effects in addition to resistance risks.     

湘南红壤丘陵区农户经济行为对土地退化的影响分析——以祁东县紫云村为例

通过在湖南省祁东县紫云材进行的土地利用及农户经济行为调查,从土地状况、从业选择、农具、农田设施、耕作方式和效益等方面,分析了湘南红壤丘陵区农户社会经济行为对土地质量的影响。结果表明：紫云村农户重“品种”轻“土壤”,水田土壤有机质含量减少,理化性状变差,土壤自然肥力降低,旱地、林地粗放经营,质量退化。改变农户只重“品种”而忽视“土壤”的观念、提高耕地复种指数、建立合理的轮作体系和水土保持型高效集约持续的耕作制度、加强林业管理和经营、加大农业投入、搞好农田水利建设是防止本区土地退化和保证本区农业可持续发展的对策。     

Does human activity impact the natural antibiotic resistance background? Abundance of antibiotic resistance genes in 21 Swiss lakes

Antibiotic resistance genes (ARGs) are emerging environmental contaminants, known to be continuously discharged into the aquatic environment via human and animal waste. Freshwater aquatic environments represent potential reservoirs for ARG and potentially allow sewage-derived ARG to persist and spread in the environment. This may create increased opportunities for an eventual contact with, and gene transfer to, human and animal pathogens via the food chain or drinking water. However, assessment of this risk requires a better understanding of the level and variability of the natural resistance background and the extent of the human impact. We have analyzed water samples from 21 Swiss lakes, taken at sampling points that were not under the direct influence of local contamination sources and analyzed the relative abundance of ARG using quantitative real-time PCR. Copy numbers of genes mediating resistance to three different broad-spectrum antibiotic classes (sulfonamides: sul1, sul2, tetracyclines: tet(B), tet(M), tet(W) and fluoroquinolones: qnrA) were normalized to copy numbers of bacterial 16S rRNA genes. We used multiple linear regression to assess if ARG abundance is related to human activities in the catchment, microbial community composition and the eutrophication status of the lakes. Sul genes were detected in all sampled lakes, whereas only four lakes contained quantifiable numbers of tet genes, and qnrA remained below detection in all lakes. Our data indicate higher abundance of sul1 in lakes with increasing number and capacity of wastewater treatment plants (WWTPs) in the catchment. sul2 abundance was rather related to long water residence times and eutrophication status. Our study demonstrates the potential of freshwater lakes to preserve antibiotic resistance genes, and provides a reference for ARG abundance from lake systems with low human impact as a baseline for assessing ARG contamination in lake water.     

不同农地整治措施对土壤细菌多样性的影响

为了研究不同农地整治措施对土壤细菌的影响,通过高通量测序技术,对不同农地整治措施下土壤细菌多样性与种群结构进行对比分析。结果表明:(1)从细菌多样性来看,实施农地整治的样点土壤细菌多样性显著提高;(2)从细菌种群结构来看,实施田块归并、平整土地、筑造沟渠以及土壤培肥等措施有效提高了甲基暖菌属(Methylocaldum)、亚硝化单胞菌(Nitrosomonas)、脱硫线菌属(Desulfonema)等有益菌属的丰度;(3)通过与土壤环境因子的相关性分析,酸碱度、铜和铅含量是影响农地整治区土壤细菌多样性与结构的重要因素。该研究证实了农地整治对提高土壤细菌多样性和改善土壤质量的重要作用,也为农地整治工作的开展提供了科学依据。     

Evaluation of food industry by-products as feed in semi-arid dairy farming systems: the case of Jordan

Dairy feeding systems in many semi-arid countries are based on imported concentrates and forages. This has economic and ecological implications given the increase in global feed prices and greenhouse gas (GHG) emissions from land use change. This paper aims to explore alternative dairy feeding systems under semi-arid conditions, using Jordan as an example. The feedings systems under investigation vary in their share of food industry by-products (replacing concentrates in the diet) and are compared against the current concentrate-based feeding systems. The systems are evaluated against three criteria: their nutritional value, their impact on the cost of milk production, and their GHG mitigation potential. Feed samples from eleven food industry by-products and ten conventional feeds were collected from food factories and from three typical dairy farms, representing the typical large-, medium- and small-scale farm types, respectively. Feed samples were analysed for their chemical composition and metabolisable energy contents. In addition, economic and production farm data were collected and entered into a model for GHGs calculation and economic evaluation. The results suggest that inclusion of locally available food industry by-products in the rations of milk cows in semi-arid production systems can be instrumental in reducing production costs and mitigating GHG emissions. Cost of milk production in the model farms can be lowered by up to 14 %; mitigation of CO₂ eq. emission ranged between 70 and 290 g CO₂ eq./kg milk. The degree to which these benefits can be reaped is positively related to the level of inclusion of by-product feeds in lactating cows’ diets.     

Farm-level assessment of CO2 and N2O emissions in Lower Saxony and comparison of implementation potentials for mitigation measures in Germany and England

Greenhouse gases (GHG) emissions from agricultural farming practice contribute significantly to European GHG inventories. For example, CO₂ is emitted when grassland is converted to cropland or when peatlands are drained and cultivated. N₂O emissions result from fertilization. Enabling farmers to reduce their GHG emissions requires sufficient information about its pressure–impact relations as well as incentives, such as regulations and funding, that support climate-friendly agricultural management. This paper discusses potentials to improve the supply of information on: farm-specific climate services or impacts, present policy incentives in Germany and England that support climate-friendly farm management and related adaptation requirements. Tools which have been developed for a farm environmental management software (to be added after review because of potential identification) are presented. These tools assess CO₂ emissions from grassland conversion to cropland and peatland cultivation, as well as N₂O emissions from nitrogen fertilization. As input data, the CO₂ tool requires a classification of soil types according to soil organic carbon storage. The input data based on soil profile samples was compared with reference data from the literature. The N₂O tool relies on farm data concerning fertilization. These tools were tested on three farms in order to determine their viability with respect to the availability of required data and the differentiation of results, which determines how well site-specific conservation measures can be identified. Assessing CO₂ retention function of grassland conservation to cropland on the test farms leads to spatially differentiated results (~100 to ~900 potentially mitigated t CO₂ ha^?1). Assessed N₂O emissions varied from 0.41 to 1.1 t CO₂eq. ha^?1 a^?1. The proposed methods support policies that promote a more differentiated funding of climate conservation measures. Conservation measures and areas can be selected so that they will have the greatest mitigation effects. However, even though present policy instruments in Germany and England, such as Cross Compliance and agri-environmental measures, have the potential to reduce agricultural GHG, they do not appear to guide measures effectively or site-specifically. In order to close this gap, agri-environmental measures with the potential to support climate protection should be spatially optimized. Additionally, the wetland restoration measures which are most effective in reducing GHG emissions should be included in funding schemes.     

Characteristics of microorganisms isolated from technogenic soils of the Kama region

Microorganisms capable of degrading monocyclic and polycyclic aromatic hydrocarbons and several chlorinated aromatic compounds were isolated from soils polluted with industrial waste from chemical plants. They were identified as representatives of the genera Pseudomonas, Flavobacterium, Alcaligenes, Rhodococcus, Microbacterium, Cellulomonas, Arthrobacter, and Brevibacterium. Among them, bacteria capable of utilizing xenobiotics in a wide range of ambient temperatures and pH and in the presence of high sodium chloride concentrations were revealed.     

Delivering on the Promise of Agroforestry

Agroforestry – the traditional practice of growing trees on farms for the benefit of the farm family and for the environment – was brought from the realm of indigenous knowledge into the forefront of agricultural research less than two decades ago. It was promoted widely as a sustainability-enhancing practice that combines the best attributes of forestry and agriculture. Based on principles of natural resource management and process-oriented research, agroforestry is now recognized as an applied science, that is instrumental in assuring food security, reducing poverty and enhancing ecosystem resilience at the scale of thousands of smallholder farmers in the tropics.Trees on farms provide both products and services: they yield food, fuelwood, fodder, timber and medicines, which farm families can use at home or take to market to bring in much-needed cash; they replenish organic matter and nutrient levels in soils and they help control erosion and conserve water. The International Centre for Research in Agroforestry, and its partners, are working to integrate the functions of trees with policy and institutional improvements that aim at facilitating wide-scale adoption by farmers.Two examples described in this paper are replenishing soil fertility in sub-Saharan Africa using short-term improved tree and shrub fallows and the results of agroforestry research to support significant land tenure policy in southeast Asia.Although just one option in sustainable land-use, science-based agroforestry has the potential to produce economically, socially and environmentally sound results for the billions of people who depend on this ancient practice and modern science.     

Factors contributing to radiocaesium variability in upland sheep flocks in west Cumbria (United Kingdom)

Following the Chernobyl accident in 1986, restrictions were placed on the movement and slaughter of sheep within upland areas of the UK because radiocaesium activity concentrations in their meat exceeded 1000 Bq kg(-1) fresh weight. Some farms remain under restriction in 2007. From 1991 to 1993 detailed studies were conducted on three sheep farms within the restricted area of west Cumbria to systematically assess the various parameters which may contribute to the observed variability in radiocaesium activity concentrations within sheep flocks. This paper reports the spatial variation in soil and vegetation activity concentrations across the grazed areas at these farms and determines the influence of grazing behaviour on variability in (137)Cs activity concentrations between individual sheep within the flocks. Together with previously reported results, these new data are used to draw conclusions on the factors determining variability within the three flocks. However, the factors are too site specific to be able to generalise the findings to other farms within the restricted areas of the UK.     

基于污染控制的畜禽养殖场适度规模的理论分析

当前,规模化逐渐成为我国畜禽养殖业发展的主要思路,而现实中大规模养殖在带来经济效益的同时也带来了严重的环境污染。从污染控制的角度看是否存在最优养殖规模成为一个需要研究的问题。基于耕地对氮磷的承载能力、运输成本、排污费等变量构建了数理模型,探讨追求利润最大化的畜禽养殖场的最优规模问题。结果表明：在养殖场自由选择养殖规模时,出售一个养殖单位获得的经济收益越高、耕地对处理剩余物的承载能力越大,则最优养殖规模越大;而一个养殖单位的直接生产成本和粪便处理成本越高、畜禽粪便经处理后的剩余物越多、运输成本越高、排污费越高,则最优规模越小。在养殖规模既定的情况下,提高排污收费时畜禽养殖场将提高其处理剩余物的还田处置比例。最后,指出在畜禽粪便处理技术难以有效去除氮磷、对养殖场是否合理处置最终剩余物难以监管的条件下,对养殖场进行规模控制将是畜禽养殖污染控制的一个政策方向