甲氧苄胺嘧啶和磺胺甲恶唑在土壤中的吸附

以OECD Guideline 106为基础,开展吸附动力学和批平衡实验,研究了磺胺甲恶唑(SMZ)和甲氧苄胺嘧啶(TMP)在土壤中的吸附过程。结果表明,相较于单室一级动力学模型,双室一级动力学模型更能准确的描述SMZ、TMP在土壤中的动态吸附过程。在3种表征吸附的模型中,Freundlich模型和DA模型较好的拟合了SMZ和TMP的吸附等温线,但Freundlich模型拟合效果更佳。对于同一种抗生素,在2种土壤中的吸附容量存在较为显著的差异性,在底泥中的吸附容量要高于包气带。     

The economic dynamics of antibiotic efficacy under open access

We analyze the exploitation of an antibiotic in a market subject to open access on the part of antibiotic producers to the common pool of antibiotic efficacy. While the market equilibrium depends only on current levels of antibiotic efficacy and infection of the epidemiological system, the social optimum accounts for the dynamic externalities which relate those levels to the intertemporal use being made of the antibiotic. We show that depending on the parameters of the model, in particular the cost of production and the improvement in the recovery rate that results from antibiotic treatment, the positive steady-state level of antibiotic efficacy to which the system tends under open access can be lower or higher than the level which should prevail in the socially optimal steady state. In fact there are parameter configurations for which the steady states can be exactly the same. However, the paths leading to the steady state always differ.     

Effects of hydraulic retention time on net present value and performance in a membrane bioreactor treating antibiotic production wastewater

• The membrane bioreactor cost decreased by 38.2% by decreasing HRT from 72 h to 36 h. • Capital and operation costs contributed 62.1% and 37.9% to decreased costs. • The membrane bioreactor is 32.6% cheaper than the oxidation ditch for treatment. • The effluent COD also improved from 709.93±62.75 mg/L to 280±17.32 mg/L. • Further treatment also benefited from lower pretreatment investment. A cost sensitivity analysis was performed for an industrial membrane bioreactor to quantify the effects of hydraulic retention times and related operational parameters on cost. Different hydraulic retention times (72–24 h) were subjected to a flat-sheet membrane bioreactor updated from an existing 72 h oxidation ditch treating antibiotic production wastewater. Field experimental data from the membrane bioreactor, both full-scale (500 m³/d) and pilot (1.0 m³/d), were used to calculate the net present value (NPV), incorporating both capital expenditure (CAPEX) and operating expenditure. The results showed that the tank cost was estimated above membrane cost in the membrane bioreactor. The decreased hydraulic retention time from 72 to 36 h reduced the NPV by 38.2%, where capital expenditure contributed 24.2% more than operational expenditure. Tank construction cost was decisive in determining the net present value contributed 62.1% to the capital expenditure. The membrane bioreactor has the advantage of a longer lifespan flat-sheet membrane, while flux decline was tolerable. The antibiotics decreased to 1.87±0.33 mg/L in the MBR effluent. The upgrade to the membrane bioreactor also benefited further treatments by 10.1%–44.7% lower direct investment.     

抗生素最小抑制浓度法(MICs)评估环境大肠杆菌抗生素抗性

2015年世界卫生组织将抗生素的滥用列为21世纪最大的挑战之一,全球范围内抗生素抗药性的散播已严重威胁人类的健康。如何检测环境中的细菌抗药性,并有效评估抗药性感染的风险,是环境微生物研究的一项重要课题。本文通过改进的培养基微量稀释(broth micro-dilution)法,确定了2个地区(中国成都和美国夏威夷)不同环境来源(天然水系和市政污水)的大肠杆菌的抗生素最小抑制浓度(minimum inhibitory concentrations,MICs)。计算所得的MIC分位数(MIC50和MIC90)、菌体抗性百分比及多抗药性指数(multiple antibiotic resistance indexes,MARIs)显示两地不同环境区划的抗生素抗性存在明显的差异。天然水系(成都锦江)中的抗生素抗性是随时间可变的,与当地的降雨事件相关。环境菌株的抗药性模式通过聚类和非度量多维测度(non-metric multidimensional scaling,NMDS)进行分析。广谱β-内酰胺酶基因筛查显示出抗性基因与抗性表型之间的正相关性。结合现有的两地抗生素的使用数据讨论了两地环境抗生素抗性与当地人类活动及抗生素的使用实践之间的紧密联系。采集环境菌株抗生素MIC数据的实验及数据分析方法实现了环境抗药性的跨时空对比,为规范抗生素的区域性使用提供了指导作用。     

Assessment of antibiotic resistance genes in dialysis water treatment processes

• Quantitative global ARGs profile in dialysis water was investigated. • Totally 35 ARGs were found in the dialysis treatment train. • 29 ARGs (highest) were found in carbon filtration effluent. • erm and mtrD-02 occurred in the final effluent. • The effluent was associated with health risks even after RO treatment. Dialysis water is directly related to the safety of hemodialysis patients, thus its quality is generally ensured by a stepwise water purification cascade. To study the effect of water treatment on the presence of antibiotic resistance genes (ARGs) in dialysis water, this study used propidium monoazide (PMA) in conjunction with high throughput quantitative PCR to analyze the diversity and abundance of ARGs found in viable bacteria from water having undergone various water treatment processes. The results indicated the presence of 35 ARGs in the effluents from the different water treatment steps. Twenty-nine ARGs were found in viable bacteria from the effluent following carbon filtration, the highest among all of the treatment processes, and at 6.96 Log (copies/L) the absolute abundance of the cphA gene was the highest. Two resistance genes, erm (36) and mtrD-02, which belong to the resistance categories macrolides-lincosamides-streptogramin B (MLSB) and other/efflux pump, respectively, were detected in the effluent following reverse osmosis treatment. Both of these genes have demonstrated the potential for horizontal gene transfer. These results indicated that the treated effluent from reverse osmosis, the final treatment step in dialysis-water production, was associated with potential health risks.     

Degradation of metronidazole by dielectric barrier discharge in an aqueous solution

The discharge characteristics during the degradation of MNZ by DBD were investigated. Increasing the discharge frequency can promote the degradation of MNZ. MNZ removal reaches 99.1% at the initial concentration of 40 ppm within 120 min. Coexisting organic matter inhibits the degradation of MNZ. The energy efficiency of DBD for MNZ removal is higher than other technologies. Degradation of metronidazole (MNZ) which is a representative and stable antibiotic by dielectric barrier discharge (DBD) in an aqueous solution has been studied. Effects of initial MNZ concentration, solution pH and coexisting organics on the degradation were investigated. The results illustrated that increasing the input power and the discharge frequency can improve the removal of MNZ. At low initial concentration, the removal of MNZ can reach up to 99.1%. Acidic and neutral conditions are more favorable for MNZ removal than alkaline condition in the early stage of degradation. However, the difference in MNZ removal between those in acidic or neutral media and that in alkaline one could be neglected with prolonging of the treatment time. Therefore, this method can be applied to MNZ degradation with a wide pH range. Coexisting organic matter in water can attenuate the removal to some extent. This study could provide valuable references for the degradation of nitroimidazole antibiotics by DBD.     

Analysis of antibiotic resistance of Escherichia coli isolated from the Yitong River in North-east China

The concentrations of four types of antibiotics in the Yitong River were detected. The concentration of total coliforms in summer was higher than that in spring. There was a seasonal difference in antibiotic resistance of E. coli. The E. coli in the Yitong River was found to have multiple antibiotic resistance. The Yitong River is one of the largest secondary tributaries of the Songhua River. The area where the Yitong River flows is densely populated and contains the livestock and poultry breeding areas of north-east China. These areas introduce a high risk of antibiotic contamination. In this study, the concentrations of four types of typical antibiotics including quinolones, tetracyclines, sulfonamides, and trimethoprim were determined by solid phase extraction-high performance liquid chromatography. The antibiotic resistance of Escherichia coli caused by antibiotic pollution was investigated. The concentration of total coliforms in the Yitong River was detected by the plate counting method. The antibiotic resistance of E. coli to quinolones, tetracyclines, sulfonamides, and trimethoprim was analyzed by the Kirby-Bauer method. The results showed that the concentration of total coliforms in the summer was higher than that in the spring. There was a seasonal difference in the resistance rate of E. coli to antibiotics except trimethoprim. The antibiotic resistance to fluoroquinolones was relatively low. The resistance rate to tetracyclines was higher during the summer. Moreover, resistance to several antibiotics was observed in all sections. This study provides basic data for research on pollution characteristics and prevention of antibiotic exposure in rivers.     

Detection of presumed genes encoding beta-lactamases by sequence based screening of metagenomes derived from Antarctic microbial mats

• Beta-lactamase genes were found in all samples from distant places in Antarctica. • Class C beta-lactamase coding genes were the most frequently found. • Diversity of sequences exceeds that of the beta-lactamases from clinical environment. Analysis of environmental samples for bacterial antibiotic resistance genes may have different objectives and analysis strategies. In some cases, the purpose was to study diversity and evolution of genes that could be grouped within a mechanism of antibiotic resistance. Different protocols have been designed for detection and confirmation that a functional gene was found. In this study, we present a sequence-based screening of candidate genes encoding beta-lactamases in 14 metagenomes of Antarctic microbial mats. The samples were obtained from different sites, representing diverse biogeographic regions of maritime and continental Antarctica. A protocol was designed based on generation of Hidden Markov Models from the four beta-lactamase classes by Ambler classification, using sequences from the Comprehensive Antibiotic Resistance Database (CARD). The models were used as queries for metagenome analysis and recovered contigs were subsequently annotated using RAST. According to our analysis, 14 metagenomes analyzed contain A, B and C beta-lactamase genes. Class D genes, however, were identified in 11 metagenomes. The most abundant was class C (46.8%), followed by classes B (35.5%), A (14.2%) and D (3.5%). A considerable number of sequences formed clusters which included, in some cases, contigs from different metagenomes. These assemblies are clearly separated from reference clusters, previously identified using CARD beta-lactamase sequences. While bacterial antibiotic resistance is a major challenge of public health worldwide, our results suggest that environmental diversity of beta-lactamase genes is higher than that currently reported, although this should be complemented with gene function analysis.     

Use of an activated carbon from antibiotic waste for the removal of Hg(II) from aqueous solution

Porous carbon has been prepared from waste antibiotic material by a chemical activation method using K(2)CO(3) as an activating reagent. Carbon was studied systematically by the adsorption of nitrogen and iodine. It was found that the process parameters such as activation temperature and activation time are crucial for preparing high-quality activated carbon. The proper choice of the preparation conditions allows to produce microporous activated carbon with a micropore volume up to 0.492 cm(3)/g and a BET surface area of 1260 m(2)/g. Adsorption of mercury(II) from an aqueous solution on antibiotic carbon was investigated under the varying conditions of agitation time, metal ion concentration and pH. The adsorption capacity of the carbon is 129 mg/g.     

Environmental pollution by antibiotics and by antibiotic resistance determinants

Antibiotics are among the most successful drugs used for human therapy. However, since they can challenge microbial populations, they must be considered as important pollutants as well. Besides being used for human therapy, antibiotics are extensively used for animal farming and for agricultural purposes. Residues from human environments and from farms may contain antibiotics and antibiotic resistance genes that can contaminate natural environments. The clearest consequence of antibiotic release in natural environments is the selection of resistant bacteria. The same resistance genes found at clinical settings are currently disseminated among pristine ecosystems without any record of antibiotic contamination. Nevertheless, the effect of antibiotics on the biosphere is wider than this and can impact the structure and activity of environmental microbiota. Along the article, we review the impact that pollution by antibiotics or by antibiotic resistance genes may have for both human health and for the evolution of environmental microbial populations.