Antimicrobial resistance among Pseudomonas spp. and the Bacillus cereus group isolated from Danish agricultural soil

From four Danish pig farms, bacteria of Pseudomonas spp. and the Bacillus cereus group were isolated from soil and susceptibility towards selected antimicrobials was tested. From each farm, soil samples representing soil just before and after spread of animal waste and undisturbed agricultural soil, when possible, were collected. Soil from a well-characterized Danish farm soil (H?jbakkegaard) was collected for comparison. The Pseudomonas spp. and B. cereus were chosen as representative for Gram-negative and Gram-positive indigenous soil bacteria to test the effect of spread of animal waste on selection of resistance among soil bacteria. No variations in resistance levels were observed between farms; but when the four differently treated soils were compared, resistance was seen for carbadox, chloramphenicol, nalidixan (nalidixic acid), nitrofurantoin, streptomycin and tetracycline for Pseudomonas spp., and for bacitracin, erythromycin, penicillin and streptomycin for the B. cereus group. Variations in resistance levels were observed when soil before and after spread of animal waste was compared, indicating an effect from spread of animal waste.     

Effect of tetracycline residues in pig manure slurry on tetracycline-resistant bacteria and resistance gene tet(M) in soil microcosms

Effects of tetracycline residues from pig manure slurry on the prevalence of tetracycline-resistant bacteria and the tetracycline resistance gene, tet(M), were studied in soil microcosms. Four types of soil microcosms were established for a period of 152 days, supplemented with combinations of pig manure slurry and a tetracycline-resistant Enterococcus faecalis, CG110, containing the tetracycline resistance gene tet(M) (on the conjugative transposon, Tn916). The prevalence of both tetracycline-resistant aerobic bacteria and tetracycline-resistant enterococci declined rapidly until day 45 where no significant differences in the levels of tetracycline-resistant bacteria in any of the four types of microcosms could be detected. tet(M) could be detected in microcosms supplemented with either pig manure slurry and/or E. faecalis CG110 (tet(M)) for the whole period (152 days). tet(M) could be detected longer than tetracycline-resistant enterococci could be isolated (limit of detection 100 CFU/g soil) probably due to viable but not culturable (VBNC) bacteria with tet(M), horizontal gene transfer of tet(M) to indigenous soil bacteria or presence of "free" DNA. The concentration of chlortetracycline and oxytetracycline were almost stable through out the experimental period, but the tetracycline concentrations had no effect on prevalence of tetracycline-resistant bacteria. The presented microcosm approach simulated natural farmland conditions well and supported results from previous field studies.     

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.     

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.     

鄱阳湖生态区长期施肥对稻田土壤碳汇效应与固碳潜力的影响

在施肥条件下确定平衡状态时,土壤有机碳含量水平对于正确评价土壤的固碳潜力和制定合理的有机物质分配措施具有重要意义。分析了前人研究的江西省有机碳储量数据并采用Jenny模型对长期不同施肥下有机碳动态数据进行模拟。结果表明,鄱阳湖生态区有机碳储量占全省的46%,以鹰潭地区最高,九江地区最低。施肥明显增强了土壤的碳汇作用,单施有机肥或有机无机肥配施（70F+30M、50F+50M、30F+70M、NPKM、NPK+S、NPK+P和NPK+C）处理的土壤有机碳含量明显高于施化肥处理,以南昌县的30F+70M、进贤县的NPKM和余江县的NPK+P处理最高,其平衡时有机碳含量和固碳潜力分别较施化肥处理提高了3061%和6115%、3017%和5496%、3826%和7479%。因此,提高鄱阳湖生态区农田有机碳密度和固碳潜力最有效方法是有机无机肥配施,其配施方式以猪粪配施化肥相对最好,配施比例以70%有机肥配施30%化肥为宜     

Long-term field application of sewage sludge increases the abundance of antibiotic resistance genes in soil

Sewage sludge and manure are common soil amendments in crop production; however, their impact on the abundance and diversity of the antibiotic resistome in soil remains elusive. In this study, by using high-throughput sequencing and high-throughput quantitative PCR, the patterns of bacterial community and antibiotic resistance genes (ARGs) in a long-term field experiment were investigated to gain insights into these impacts. A total of 130 unique ARGs and 5 mobile genetic elements (MGEs) were detected and the long-term application of sewage sludge and chicken manure significantly increased the abundance and diversity of ARGs in the soil. Genes conferring resistance to beta-lactams, tetracyclines, and multiple drugs were dominant in the samples. Sewage sludge or chicken manure applications caused significant enrichment of 108 unique ARGs and MGEs with a maximum enrichment of up to 3845 folds for mexF. The enrichment of MGEs suggested that the application of sewage sludge or manure may accelerate the dissemination of ARGs in soil through horizontal gene transfer (HGT). Based on the co-occurrence pattern of ARGs subtypes revealed by network analysis, aacC, oprD and mphA-02, were proposed to be potential indicators for quantitative estimation of the co-occurring ARGs subtypes abundance by power functions. The application of sewage sludge and manure resulted in significant increase of bacterial diversity in soil, Proteobacteria, Acidobacteria, Actinobacteria and Chloroflexi were the dominant phyla (> 10% in each sample). Five bacterial phyla (Chloroflexi, Planctomycetes, Firmicutes, Gemmatimonadetes and Bacteroidetes) were found to be significantly correlated with the ARGs in soil. Mantel test and variation partitioning analysis (VPA) suggested that bacterial community shifts, rather than MGEs, is the major driver shaping the antibiotic resistome. Additionally, the co-occurrence pattern between ARGs and microbial taxa revealed by network analysis indicated that four bacterial families might be potential hosts of ARGs. These results may shed light on the mechanism underlining the effects of amendments of sewage sludge or manure on the occurrence and dissemination of ARGs in soil.     

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.     

Costs of the Wastewater Standard in Pig Production in Mexico

The objective of this article is to address the environmental costs of pig farms in the La Piedad region Mexico, through an analysis of the standard on wastewater discharges to national water bodies. Field work was carried out from April to September 1999; a survey was conducted on 23 farms and samples of wastewater were taken on 11 farms. Pig production is the third most important system in Mexican livestock production. Heterogeneity in production systems, dependence on imported inputs (genetics and feed grains), and weak internalization of environmental costs are the main characteristics of pig production in Mexico. With no specific environmental regulations on intensive livestock activities at the municipal or state levels, Mexican Official Standard 001 on wastewater discharges is the only environmental obligation that pig farms must meet. Standard 001 on wastewater contains the maximum permissible limits for 20 contaminant parameters, and is based on a cost-benefit analysis that points to secondary treatment for the regulation’s economic viability. Investment in treatment systems and the fees that pig producers must pay when they fail to comply with the limits stipulated in the regulation, are estimated assessed as an approach to environmental costs. In order to remain within the limits in the standard, pig farms must invest in tertiary treatment, and that makes meeting the standard unaffordable for this sector.     

长期施肥对小麦—玉米轮作红壤抗蚀性的影响

为探讨不同施肥处理对红壤旱地土壤理化性状和抗蚀性影响,以长期定位施肥试验小区为研究对象,研究了CK（荒草地）、T1（不施肥）、T2（施有机肥）、T3（施氮磷钾肥）和T4（氮磷钾肥与秸秆配施）5种处理的土壤理化性状及土壤抗蚀性。结果表明：（1）荒草地开垦后,土壤容重降低,土壤孔隙度和含水量升高;相较于不施肥,施肥提高土壤有机质含量、改善土壤物理性质作用更为明显;（2）衡量不同施肥处理土壤抗蚀性的2个最佳指标为>0.25 mm水稳性团聚体含量和结构破坏率;（3）使用主成分分析综合指数表示不同处理土壤抗蚀性依次为：T2>CK>T3>T4>T1,荒草地开垦后,耕种会降低土壤抗蚀性,但施肥能略微提升土壤抗蚀性,而施有机肥提升最为明显。研究结果可为区域内农业生态系统持续发展及农田水土保持工作提供依据。     

Influence of copper status on the accumulation of toxic and essential metals in cattle

The aim of the present study was to assess whether the use of pig slurry and associated copper accumulation in calves grazing pastures fertilized with pig slurry from the Deza region in NW Spain has a significant influence on toxic metal and essential metal levels, and to investigate whether copper accumulation is correlated with the levels of these other metals. Correlations between copper, toxic metals (cadmium, lead) and essential metals (molybdenum, iron, zinc, selenium, manganese and cobalt) concentrations were evaluated in liver and kidney of 195 calves from the region of Deza. Metal concentrations were determined by ICP-OES and correlations between pairs of elements by Pearson correlation analysis. There was a strongly significant positive association between copper and lead in the liver. Considering the trace metals, copper in the liver showed significant positive correlations with cobalt in both liver and kidney, and with molybdenum in the liver. In addition, significant correlations were observed between copper and most essential metals in kidney. These associations are similar to those found in different animal species experimentally dosed with copper and other metals, as well as in cattle exposed to normal copper concentrations.     

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.     

水培芹菜净化不同浓度沼液的试验研究

沼液是畜禽粪尿经厌氧发酵产生的发酵液,随意排放将对环境产生一定危害,有效利用将带来一定的经济效益。用沼液水培芹菜,不仅可以为芹菜提供丰富的营养物质,还能达到废物资源化利用的目的。通过生物浮床工艺,将芹菜水培于不同浓度沼液中,研究其生长特性及其对污染物的去除能力,得出用沼液水培芹菜的最佳稀释倍数。结果表明:经过80 d的种植,稀释30倍的沼液水培的芹菜生物增长量最大;随着沼液稀释倍数的增加,芹菜的茎叶部分与根部中N的质量分数越小。芹菜对稀释100倍沼液中TN的去除率最高,为94.6%;对稀释10倍沼液中TP的去除率最高,为90.6%。沼液经稀释20~50倍之后水培芹菜的TN、TP去除率都较高;稀释30~40倍沼液水培芹菜所取得的环境效益和经济效益较高。     

不同种植方式对稻茬紫云英的生长及土壤养分的影响

研究绿肥作物种植方式对其生长状况及土壤特性的影响，可为长江下游农区“水稻(Oryza sativa L.)—绿肥作物”轮作模式下如何以草增粮提供科学依据。于2018~2019年在江苏省昆山市采用套播留茬、浅旋直播、板茬直播3种种植方式，研究不同绿肥种植方式对自身群体基础、越冬稳定性、生育进程、主要形态指标、产草量及还田后土壤养分动态的影响。结果表明，相同播种量水平下，浅旋直播的群体起点最高，为58.29万基本苗/hm ²；越冬稳定性以套播留茬方式最高，越冬率为94.3%。不同种植方式下生育进程递进规律总体一致，主要影响绿肥作物的营养生长期，套播留茬方式的营养生长期最长（122 d），比最短的浅旋直播方式高出20 d。套播留茬方式下的株高、茎粗及其他主要形态指标明显高出其他两种方式。套播留茬方式的鲜草产量最高，浅旋直播方式居中，板茬直播方式最低，且均超过30 000 kg·hm^-2。翻压还田后，3种方式下土壤有机质、全氮、铵态氮、硝态氮、速效磷、速效钾等土壤养分含量均有一定的增加，其中套播留茬方式增加幅度最高。     

四川省畜禽粪便排放时空分布及污染防控

掌握畜禽粪便的时空分布,有利于高效防控其污染环境的可能。采用排污系数法,估算出2000～2015年间四川省畜禽粪便、COD及氮磷产生量,在此基础上,分析了2015年四川省畜禽粪便的排放时空分布特征与畜禽粪便、氮、磷污染情况。结果表明：（1）2000～2015年,四川省畜禽粪便平均产生量约2.10亿t猪粪当量,其中猪、牛、家禽是当地环境威胁的主要畜禽种类;（2）2015年四川省产沼气潜力可观,但大部分地区受到畜禽粪便污染,其中德阳市、雅安市两地预警级别达Ⅵ级,对环境影响严重;（3）2015年四川省氮、磷耕地负荷的平均值分别为78.45 kg/hm2和13.57 kg/hm2,均低于欧盟的限量标准（氮170 kg/hm2、磷35 kg/hm2）,但大部分地区面临氮、磷污染风险。其中成都市、德阳市、雅安市氮、磷污染风险均较高,自贡市、泸州市等氮、磷污染风险整体不高,但畜禽养殖量近50%环境容量,这些地区应做好畜禽养殖总量控制及污染物消减措施。 关键词： 畜禽养殖;粪便污染;时空分布;污染防控;四川     

Are the parasiticidal avermectins resistant to dissipation in the environment? The case of eprinomectin

Eprinomectin (EPM) is a veterinary drug currently licensed in many countries for the treatment of endo- and ecto-parasites in cattle. Despite the notable evidence for its high toxicity to the terrestrial and aquatic environment ecosystems, its environmental behavior and fate are currently unknown. In the present research, the dissipation of EPM was studied in three soils and in cattle manure by using the OECD 307 guideline and the recently developed European Medicines Agency (EMA/CVMP/ERA/430327) guideline, respectively. The procedure presented by the FOrum for Co-ordination of pesticide models and their USe (FOCUS) was adopted for estimating the EPM degradation kinetics in soil and cattle manure. The EPM dissipation in soil was best described by the SFO (Simple First Order) and the HS (Hockey Stick) models, under aerobic and anaerobic conditions, respectively. The EPM dissipation in cattle manure was best described by the FOMC (First Order Multi Compartment) model. The Dissipation Time for the 50% of the initial EPM mass (DT₅₀) range was 38–53 days under aerobic and 691–1491 days under anaerobic conditions. In addition, the DT₅₀ for EPM in cattle manure was 333 days. Therefore, EPM could be characterized as moderately to highly persistent to dissipation in soil, which depends on soil type, its oxygen content (aerobic or anaerobic conditions in soil) and the microbial activity. Moreover, the EPM resists dissipation in cattle manure, resulting to a high load in soil after manure application in agricultural land (or direct defecation in grassland). Consequently, the high possibility for EPM accumulation in soil and cattle manure should be considered when assessing the environmental risk of the drug.     

水葫芦资源化处置与综合利用研究评述

水葫芦（凤眼莲）是一种源自南美的浮水植物。由于人为引入,水葫芦已经遍布整个热带、亚热带地区,带来了诸如鱼类减产、影响捕鱼、堵塞航道等问题。水葫芦木质素、纤维素含量高,含水率大,因此处置处理困难;同时由于水葫芦种子存活时间长、繁殖速度快,所以水葫芦的控制至今仍是个难题。简要阐述了水葫芦的生物学特性及现有的控制方法;对水葫芦的化学组成研究进行了总结;将其资源化处置方式归纳为制备燃料（固体燃料、液体燃料及气体燃料）、饲料（干饲料、青贮饲料）和肥料（有机肥、绿肥）３种方式,在对各项技术分别评述的基础上进行了比较。提出制备沼气燃料和有机肥是水葫芦目前较有前景的利用方式。但对于农村地区的水葫芦处置来说,简易的堆肥和绿肥还田是更为合适的处置方式。     

Poverty and the Deterioration of Natural Soil Capital in the Peruvian Altiplano

The Peruvian altiplano is a marginal agricultural region with limited infrastructure, climate constraints, and high levels of poverty. Data were collected from 265 farms in four different agricultural regions, and data from three of those regions are analyzed here. Regressions were run with soil nutrient loss, soil depth loss, and yield loss over the past 20 years, as perceived by farmers. Location, topographical and management factors were considered. Additional regressions were run to examine the determinants of two agricultural management practices which were found to affect soil quality, namely fallowing and ploughing vertical furrows. Use of traditional fallowing (aynoca) was associated with helping to preserve soil quality, and was practiced by households with more education, with higher non-farm income, and in villages which had benefitted from natural resource development projects. Vertical furrowing similarly was associated with helping preserve soil quality, and was practiced by households with fewer unmet basic needs. These results have implications for the agricultural and development strategies to be followed in the region.     

A new concept of carbon dioxide accelerated ammonia release from liquid manure in pig house

Indoor air quality in animal buildings is very important to the health of agricultural workers and animals. Carbon dioxide (CO2) and ammonia (NH3) are two of the most important pollutants in pig houses. Four tests were conduced in a mechanically ventilated pig house to study release behaviors of CO2 and NH3 from liquid manure using impulse, pulse and step ventilation inputs. The CO2 and NH3 concentrations were sampled in the exhaust chimney and measured with a CO2 monitor and a NOx analyzer, respectively. The ventilation rate was measured with a ventilation rate sensor in the chimney. A new phenomenon, characterized by a delayed dynamic response of NH3 release to the high ventilation inputs as compared with the response of CO2 release, was encountered. A new CO2 factor was identified as the cause of the delayed NH3 response. An original concept of Carbon-dioxide Accelerated Ammonia Release (CAAR) was developed. It explained that, at the initial stage of gas release induced by the high ventilation, the high release of CO2 gradually raised the pH in the surface manure. The increased pH accelerated the release of NH3. The higher release of NH3 had a negative feedback to the pH. The effects of CO2 and NH3 releases on the pH finally reached a dynamic equilibrium. The NH3 release under the dynamic equilibrium was greatly accelerated compared to that under initial conditions.     

Yield and arsenate uptake of arbuscular mycorrhizal tomato colonized by Glomus mosseae BEG167 in As spiked soil under glasshouse conditions

A glasshouse pot experiment was conducted to study the effect of arbuscular mycorrhizal (AM) colonization by Glomus mosseae BEG167 on the yield and arsenate uptake of tomato plants in soil experimentally contaminated with five As levels (0, 25, 50, 75 and 150 mg kg(-1)). Mycorrhizal colonization (50-70% of root length) was little affected by As application and declined only in soil amended with 150 mg As kg(-1). Mycorrhizal colonization increased plant biomass at As application rates of 25, 50 and 75 mg kg(-1). Shoot As concentration increased with increasing As addition up to 50 mg kg(-1) but decreased with mycorrhizal colonization at As addition rates of 75 and 150 mg kg(-1). Shoot As uptake increased with mycorrhizal colonization at most As addition levels studied, but tended to decrease with addition of 150 mg As kg(-1). Total P uptake by mycorrhizal plants was elevated at As rates of 25, 50 and 75 mg kg(-1), and more P was allocated to the roots of mycorrhizal plants. Mycorrhizal plants had higher shoot and root P/As ratios at higher As application rates than did non-mycorrhizal controls. The soil of inoculated treatments had higher available As than uninoculated controls, and higher pH values at As addition levels of 25, 50 and 75 mg kg(-1). Mycorrhizal colonization may have increased plant resistance to potential As toxicity at the highest level of As contamination studied. Mycorrhizal tomato plants may have potential for phytoextraction of As from moderately contaminated soils or phytostabilization of more highly polluted sites.