Antibacterial effects of Anodonta cygnea fluids on Escherichia coli and enterococci multi-drug-resistant strains: environmental implications

The persistence of bacteria in Anodonta cygnea largely depends on the hemolymph bactericidal activity against aquatic micro-organisms.

The aim of this study was to assess the in vitro bactericidal activity of whole hemolymph against multi-drug-resistant Escherichia coli and enterococci strains. Four mussels were injected with multi-resistant strains of E. coli in order to determine their in vivo bactericidal reactivity. In vitro experiments showed that the hemocytes viability decreased almost 70% in 4 h, the same happened in the control hemolymph. Enterococci tested in in vitro experiments were more susceptible than E. coli to whole hemolymph and hemocytes fractions. None of the enterococci bacteria was detected in the hemolymph fractions from 24 to 72 h, while E. coli was still detectable 72 h after inoculation both in the control and respective plasma fractions. The microbial inhibition on both hemolymph and cell pellets suggest that hemocytes may be the main responsibles for that process.

In vivo experiments showed that hemolymph inhibited the E. coli load injected and it was correlated with a high tendency for the increase in hemocytes counts, after 72 h. High adherence of E. coli and an intense pseudopods manifestation, mainly to the granulocytes, suggest a clear phagocytosis process.     

Enhanced disinfection of <Emphasis Type="Italic">Escherichia coli</Emphasis> and bacteriophage MS2 in water using a copper and silver loaded titanium dioxide nanowire membrane

Titanium dioxide (TiO₂) is a widely used photocatalyst that has been demonstrated for microorganism disinfection in drinking water. In this study, a new material with a novel structure, silver and copper loaded TiO₂ nanowire membrane (Cu-Ag-TiO₂) was prepared and evaluated for its efficiency to inactivate E. coli and bacteriophage MS2. Enhanced photo-activated bactericidal and virucidal activities were obtained by the Cu-Ag-TiO₂ membrane than by the TiO₂, Ag-TiO₂ and Cu-TiO₂ membranes under both dark and UV light illumination. The better performance was attributed to the synergies of enhanced membrane photoactivity by loading silver and copper on the membrane and the synergistic effect between the free silver and copper ions in water. At the end of a 30 min test of deadend filtration under 254 nm UV irradiation, the Cu-Ag-TiO₂ membrane was able to obtain an E. coli removal of 7.68 log and bacteriophage MS2 removal of 4.02 log, which have met the US EPA standard. The free metal ions coming off the membrane have concentrations of less than 10 ppb in the water effluent, far below the US EPA maximum contaminant level for silver and copper ions in drinking water. Therefore, the photo-activated disinfection by the Cu-Ag-TiO₂ membrane is a viable technique for meeting drinking water treatment standards of microbiological water purifiers.

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Photo- and electro-catalysis for solar disinfection of Escherichia coli-contaminated water using Ag–TiO2/graphite

A titanium dioxide film on a graphite substrate was synthesized by chemical bath deposition from TiCl₄ as precursor and with the surfactant cetyl trimethyl ammonium bromide as a linking and assembling agent. Silver was loaded on the TiO₂ film by electrodeposition at 0.025?A. Water contaminated with Escherichia coli was disinfected under sunlight irradiation by photolysis (Lys), photocatalysis (PC), photoelectrocatalysis (PEC), and electrocatalysis (EC). The highest rate constant, k, was achieved with EC; k was 5.1?×?10^?2 colony forming units (CFU) mL^?1?min^?1. However, auto-oxidation of Ag occurred during EC and PEC. Meanwhile, the rate constant of disinfection by means of PC was lower than EC and PEC, and k was 3.82?×?10^?2 CFU?mL^?1?min^?1. Nevertheless, the auto-oxidation of Ag in the Ag–TiO₂/graphite tablet did not occur during the disinfection process.     

Bacterial toxicity testing and antibacterial activity of parabens

Parabens are used because of their antimicrobial effects, yet they have multiple adverse effects. The aim of this work was to evaluate the bactericidal activity and bacterial toxicity of the most common parabens: methylparaben, ethylparaben, propylparaben, isopropylparaben, butylparaben, isobutylparaben and phenylparaben. The bactericidal action was evaluated by means of the dilution-neutralization method against Escherichia coli and Staphylococcus aureus, and the biotest of inhibition of growth of E. coli was applied for the bacterial toxicity assay. Bactericidal concentrations were reached only for propylparaben, butylparaben and isobutylparaben. The toxicity study showed methylparaben to be the least toxic, whereas the most toxic one was phenylparaben. It can be concluded that the disinfectant activity of the parabens studied is insignificant against S. aureus and E. coli. Acute toxicity is very low, and the inhibitory effect is weak. Our results provide information about the risk–benefit balance of parabens use.     

Removal of arsenic (V) from aqueous medium using manganese oxide coated lignocellulose/silica adsorbents

Arsenic (V) adsorption on manganese oxide coated rice wastes was investigated in this study. The modified adsorbents were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, and pH measurements to determine the point of zero charge. Batch adsorption equilibrium experiments were conducted to study the effects of pH, contact time, and initial concentration on arsenic removal efficiency. The adsorption capacity of rice waste was significantly improved after modification with permanganate. The Langmuir isotherm model fitted the equilibrium data better than the Freundlich model which confirms surface homogeneity of the adsorbent. Maxima adsorption capacities are determined as 10 and 12 mg/g at pH 3 for manganese oxide coated rice husk and straw, respectively. The adsorption energy indicates that the adsorption process may be dominated by chemisorption. Pseudo-second-order rate equation described the kinetics sorption of arsenic with good correlation coefficients, better than a pseudo-first-order equation. Manganese oxide coated rice husk and straw appear to be promising low cost adsorbents for removing arsenic from water.     

Removal of chromium(VI) by ZnCl2 activated coir pith carbon

The adsorption of chromium(VI) onto ZnCl₂ activated carbon developed from coir pith was investigated to assess the possible use of this adsorbent. The influence of contact time, adsorbent dose, Cr(VI) concentration, pH and temperature were investigated. The two theoretical adsorption isotherms, namely, Langmuir and Freundlich were used to describe the experimental results. The Langmuir adsorption capacity (Q ₀) was found to be 120.5?mg Cr(VI) per g of the adsorbent. The adsorption followed the second-order kinetics and was found to be maximum at pH 2.0. The pH effect and the desorption studies showed that ion exchange mechanism might be involved in the adsorption process. The effects of foreign ions such as chloride, sulphate, phosphate, selenite, molybdate, nitrate and perchlorate on the removal of Cr(VI) have been investigated. The removal of Cr(VI) from synthetic ground water was also tested. The results show that ZnCl₂ activated coir pith carbon is effective for the removal of Cr(VI) from water.     

Effect of boundary layer transport on the fixation of carbon by the giant kelp Macrocystis pyrifera

The uptake of inorganic carbon into the thallus of Macrocystis pyrifera (L.) C. Ag. requires first that the inorganic carbon pass through the water medium to the plant surface. This transfer of inorganic carbon to the thallus must take place through a boundary layer. Experiments in water tunnels indicate that the boundary layer adjacent to the M. pyrifera blade may be turbulent in water speeds as low as 1 cm sec^-1. Photosynthetic output of the blade can be increased by a factor of 300% by increasing water speeds over the blade surface from 0 to 4 cm sec^-1. This is consistent with a decrease in the thickness of the boundary layer. Above 4 cm sec^-1, the assimilation of carbon was limiting. The assimilation of carbon is generally known to follow Michaelis-Menten-like kinetics. Combining the two uptake steps into an overall model of carbon uptake agrees well with photosynthetic data obtained from M. pyrifera under varying conditions of water speed and bicarbonate concentrations in the laboratory. The ecological and morphological consequences of these findings are discussed.     

The influence of storage on antibacterial activity of sea water. I. Experiments with sea water stored at 18°C

Three sea-water samples of about 25 l each, stored at 18°C in the dark, were examined for antibacterial activity and bacterial content. Serratia marinorubra mainly was used as test bacterium. During storage for 197 to 454 days, bactericidal capacity varied considerably. In raw sea water, extreme log (N ₃–N ₀) values (N: number of colony-forming test bacteria/ml after 0 and 3 days of any test) were higher than-1 and lower than-4. Antibacterial activity of filtersterilized and autoclaved, stored, sea water likewise varied, but to a lesser degree. The number of colony-forming marine bacteria fluctuated about 3 orders of magnitude. Variations in bacterial content and in bactericidal action of stored sea water were positively correlated during the first months of storage; later, this correlation became negative. From these results it is concluded that variations in nutrient concentration — due to successive periods of growth and autolysis of marine bacteria — were the primary reason for the changes observed in antibacterial activity of stored sea-water samples.     

Wassertechnische Strategien zur Reduzierung der Trinkwasserbelastung durch Arzneimittelwirkstoffe

Results The available research results concerning the application of innovative methods of wastewater and drinking water purification to eliminate pharmaceuticals are summarized in the present paper. An increase of the activated sludge (aerobic sludge) age to 8–10 days in treatment plants can improve the metabolization of less persistent pharmaceutical agents whereas expansion of the sojourn time beyond 10 days will not result in a remarked increase of degradation for most pharmaceutical substances. First results have shown that wastewater treatment plants with integrated membrane bioreactors (MBR) using micro- and ultrafiltration membranes do not provide significantly better results compared to the conventional wastewater treatment plants with respect to the removal of organic micropollutants (including pharmaceutical residues). The use of powdered carbon in biologically treated wastewater is able to reduce pharmaceutical residues up to 80?% in the run-off water. Pilot studies scrutinize the treatment of highly contaminated effluents via catalytic photooxidation. Regarding the suitability of the method to reduce the contamination of drinking and wastewater with pharmaceuticals yet only few data from laboratory scale testing are available. Activated carbon filtration is preferably used for drinking water treatment. Primarily against the background of disinfection, ozonation is widely used for drinking water treatment, but for wastewater treatment the method is still at the experimental stage and will hardly become of practical importance because of high costs. Sustainable wastewater separation is grounded on decentralized concepts by considering material cycles (recycling) at the place of origin. In the long term, separation measures can significantly contribute to declining drug concentrations in drinking water. Regarding the quarrying of drinking water by bank filtration water, river water or artificially enriched ground water, end-of-pipe techniques are vital. Most commonly, activated carbon or activated carbon combined with ozonization is applied and assures a high drinking water quality. Discussion The advantages and disadvantages of the different water treatment methods mainly concern the varying degrees of effectiveness with respect to the elimination of very persistent pharmaceutical agents, the generation of problematical metabolites and additional waste materials, hygienic problems, energy needs and the necessity to employ appropriate technical staff for operation. Although the biodegradation of very persistent drugs cannot be enhanced by an extension of the activated sludge age, this modification should be considered in sewage plants to reduce the contamination with less persistent medical agents. Compared with conventional wastewater treatment, membrane bioreactors provide the advantage of a better control of biological activities on the plant and a comparably small plant size but high investment and operation costs. Additionally, pharmaceuticals such as carbamazepin are only insufficiently removed from wastewater by membrane bioreactors. The regular use of powdered activated carbon in sewage treatment plants would also increase the costs of wastewater treatment and would additionally exclude the further use of sewage sludge in agriculture. Currently, in Germany the further use of sewage sludge is handled differently by the Federal States and discussed controversially. The implementation of ozonation as an additional treatment method in wastewater treatment plants is not realistic because of cost concerns. Additionally, the method produces analytically as yet not assessed metabolites with unknown (eco-)toxicological impacts. For this reason ozonation should currently not be applied unless the reaction products are removed subsequently by filtration through activated carbon. For industrial sewage photooxidation is in a state of testing but an application for municipal wastewater is, up to now, out of question. When river bank filtration is used for the supply of drinking water the use of activated carbon for purification should be essential. The lifetime of the filters is often defined by the filter capacities to eliminate radiocontrast media (e.?g., iopamidole, amidotrizoic acid). Many water supply companies already apply the ozonization prior to activated carbon filtration which supports the elimination of pharmaceuticals from the sewage. The unique developmental potential of the wastewater separation can be seen in the possibility to link up these methods with sustainable exploitation techniques and concepts (re-use of sanitized water, production of fertilizer, compost and biogas). Wastewater separation will not make ‘middle/end-of-pipe’ techniques dispensable but will make their handling more effective because concentrations of pharmaceutical agents are higher in separated effluents compared to those usually found in municipal wastewater, which in mixing sewage systems is even diluted by surface runoff. Conclusions Following today’s state of knowledge activated carbon filtration (eventually coupled with ozonization) is best suited to remove drug residues and other xenobiotics from raw water. Water works that do not apply the activated carbon filtration technique for cleanup of bank filtration water should consider an upgrade. The ozonization is primarily required for disinfection of the water. As no acute health hazard proceeds from drinking water contamination by pharmaceuticals at the present time, the upgrade of wastewater treatment plants by one of the aforementioned innovative methods is currently not required in view of drinking water quality. This offers the opportunity to develop sustainable approaches that already aim to reduce drug contaminations of wastewater and hence of ground-, surface- and drinking water. Recommendations and perspectives On a short- to mid-term perspective enriched sewage of hospitals, nursing homes and other medical facilities should be collected and treated separately. From a technical point of view the conditioning of separated hospital effluents (yellow- and greywater) via activated carbon or membrane filtration is possible but should be combined with disinfection. On a mid- and long-term scale sustainable sanitary concepts based on wastewater separation (black-, grey- and/or rainwater) associated with the recycling of mineral nutrients (nitrogen, phosphorous and potassium) should be realized for development, industry and trade areas, buildings with public lavatories, airports, motorway service areas, and large office and hotel buildings. Strategies focusing primarily on up-grading of municipal wastewater treatment plants are currently existing but the related technologies are largely in a test phase. This is why a particular technique should not be favored at the moment. The combination of various techniques (i.?e., ozonization combined with activated carbon filtration) is known to be very efficient for the removal of pharmaceutical residues from water, but the combination cannot be expected to become of importance in treatment of domestic wastewater because of high costs. Moreover, improvement of wastewater treatment technologies to remove pharmaceutical residues will not make the employment of end-of-pipe techniques in water works redundant and therefore will not lead to saving of expenses.     

Health Impact Evaluation of Boron in Drinking Water: A Geographical Risk Assessment in Northern France

Objective: To evaluate health impact of boron in drinking water. Methods: A regional scale geographical study in Northern France was conducted. Assessment of boron blood levels in a group of 180 healthy individuals and correlation with boron content in drinking water were followed by an assessment of health indicators such as birth rates, mortality rates, and sex ratios in zones of different boron content in drinking water. Results: After necessary adjustments, men living in municipalities with more than 0.30 mg/L of boron in drinking water had elevated but not significant boron blood levels compared with those living in municipalities with boron water levels of less than 0.30 mg/L (159.1 versus 123.0 ng/g; p > 0.05). The standardized birth ratio adjusted for the reference geographic zone and calendar time period was 1.07 and 1.28 in the low and high (>0.3 mg/L) boron content municipalities, respectively. The birth rate in municipalities with high boron content in drinking water was higher than that of the reference geographic zone and of the French general population (p < 10^-4). The standardized mortality ratio adjusted for the reference geographic zone and calendar time period was 0.94 and 0.92 in the low and high boron content municipalities, respectively. The mortality rate in municipalities with high boron content in drinking water was less than that of the reference geographic zone and of the French general population (p < 10^-3). No statistical difference was noted in the male–female sex ratios between the different municipality zones (p = 0.45). Conclusions: The results of this study do not support the idea of a deleterious effect of boron on human health, at the boron water level contents found in this specific region. In fact, there is a tendency toward a beneficial effect with low-dose environmental exposure (less than 1 mg/L of boron) in drinking water.     

Presence,dissemination and removal of antibiotic resistant bacteria and antibiotic resistance genes in urban drinking water system: A review

Reviewed the change of ARGs and ARB in full-scale urban drinking water systems. Conventional processes are more promising than BAC process in ARGs removal. Mechanisms of ARGs enrichment and spread in BAC filter and DWDSs are discussed. Raise the need of future research on ARGs and ARB change in building plumbing systems. Antibiotic resistance in aquatic environment has become an important pollution problem worldwide. In recent years, much attention was paid to antibiotic resistance in urban drinking water systems due to its close relationship with the biosafety of drinking water. This review was focused on the mechanisms of antibiotic resistance, as well as the presence, dissemination and removal of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the urban drinking water system. First, the presence of ARB and ARGs in the drinking water source was discussed. The variation of concentration of ARGs and ARB during coagulation, sedimentation and filtration process were provided subsequently, in which filtration was proved to be a promising technology to remove ARGs. However, biological activated carbon (BAC) process and drinking water distribution systems (DWDSs) could be incubators which promote the antibiotic resistance, due to the enrichment of ARGs and ARB in the biofilms attached to the active carbon and pipe wall. Besides, as for disinfection process, mechanisms of the inactivation of ARB and the promotion of conjugative transfer of ARGs under chlorine, ozone and UV disinfection were described in detail. Here we provide some theoretical support for future researches which aim at antibiotic resistance controlling in drinking water.     

Large-scale disinfection of real swimming pool water by electro-oxidation

Swimming pool users are a source of various contaminants and microorganisms. Conventional chlorine-based reagents treatment is commonly used to disinfect water. However, this disinfection treatment has serious serious health issues such as formation of carcinogenic by-products, i.e., trihalomethanes. In order to prevent this problem, an electrochemical disinfection process was carried out using synthetic and real swimming pool waters. The performance of the electrochemical system was evaluated by studying the effect of current intensity (0.5–3.0 A), treatment time, type of anode (Nb/BDD and Ti/Pt) and the initial concentration of pathogens Escherichia coli and P. aeruginosa. Results show that real swimming pool water, initially containing 10⁶ CFU/100 mL of pathogens, was disinfected at current intensities of 1.5 and 3.0 A using, respectively, Nb/BDD and Ti/Pt as anode materials (CFU: colony-forming units, BDD: boron-doped diamond). This work is also one of the few showing the up-scaling of electrochemical disinfection of real swimming pool water at large volumes of 100 L.     

莱州湾近岸海域中典型抗生素与抗性细菌分布特征及其内在相关性

为了揭示海陆衔接区环境中抗生素与抗性细菌分布特征及其内在相关性,以莱州湾及其主要入海河流为研究区域,利用HPLC-MS/MS分析样品中15种磺胺类抗生素(SAs)和6种喹诺酮类抗生素(QNs)的浓度,并通过改良的Method 1604(US EPA)评估海水与沉积物中2种典型水传病原微生物大肠杆菌(E.coli)与金黄色葡萄球菌(S.aureus)的抗生素抗性水平,进而探讨该区域水体中抗性菌株的分布特点以及微生物抗性率与相应抗生素浓度的相关性。结果显示,莱州湾水体与沉积物中普遍存在磺胺与喹诺酮类抗生素残留及抗性污染问题。两大类抗生素在水体中平均残留浓度分别为3.89 ng·L~(-1)(SAs)和234.68ng·L~(-1)(QNs),在沉积物中分别为0.91 ng·g~(-1)(SAs)和49.37 ng·g~(-1)(QNs),且分布特征基本呈现自河流向海洋逐渐递减的趋势,说明河流输入是莱州湾抗生素污染的主要来源。在水体中,具有磺胺类抗性的E.coli和S.aureus平均检出量分别达到2 018和4 683 CFU·L~(-1),抗性率范围分别在0%~37.3%和10.6%~45.8%之间;而2种喹诺酮类抗性病原微生物的平均检出量则相对较低,分别为1 315 CFU·L~(-1)(E.coli)和1 461 CFU·L~(-1)(S.aureus),抗性率分别为0%~50.0%和0%~20.8%;此外,相比于E.coli,S.aureus为沉积物中的主要抗性病原微生物,磺胺与喹诺酮类抗性S.aureus检出率均高于80%,平均检出量分别为24CFU·g~(-1)和18 CFU·g~(-1)。相关性分析表明,莱州湾近岸海域水体中磺胺类抗生素浓度与磺胺类抗性微生物总量之间具有良好的线性关系,然而其与微生物抗性率之间并未表现出相似的规律,说明近岸海洋环境中抗生素的残留量不是影响抗性菌株丰度的唯一因素。     

Role of carbonic anhydrase in the supply of inorganic carbon to the giant clam—zooxanthellate symbiosis

The mechanism whereby inorganic carbon (C_i) is acquired by the symbiotic association between the giant clam (Tridacna derasa) and zooxanthellae (Symbiodinium sp.) has been investigated. C_i in the haemolymph of the clam is in equilibrium with the surrounding sea water. The photosynthesis rate exhibited by the intact clam varies as a function of the C_i concentration in the clam haemolymph. The gill tissue contains high carbonic anhydrase activity which may be important in adjusting the C_i equilibrium between haemolymph and sea water. Zooxanthellae (Symbiodinium sp.) isolated from the clam mantle prefer CO₂ to HCO ₃ ^- as a source of inorganic carbon. The zooxanthellae have low levels of carbonic anhydrase on the external surface of the cell; however, mantle extracts display high carbonic anhydrase activity. Carbonic anhydrase is absent from the mantle of aposymbiotic clams (T. gigas), indicating that this enzyme may be essential to the symbiosis. The enzyme is probably associated with the zooxanthellae tubes in the mantle. The results indicate that carbonic anhydrase plays an important role in the supply of carbon dioxide within the clam symbiosis.     

Contaminants in drinking water and its mitigation using suitable adsorbents: an overview

Various options are applicable for the removal of water pollutants included reverse osmosis, ion exchange, coagulation, co-precipitation, catalytic reduction, herbal filtration, electrodialysis and adsorption. This paper deals with the sorption phenomena for the removal of pollutants from drinking water. Attempts have been made to use low cost sorbents developed by pretreatment/activation/impregnation with alkalis, acids, iron oxide, manganese dioxide, ferric chloride, alum, lime, aluminum salts with natural products/indigenous minerals viz. activated alumina, activated carbon, groundnut husk, saw dust, chemically coated sand, fly ash, zeolites, clay minerals and other plant products. Application of Freundich and Langmuir isotherms were used to assess the adsorption capacity. Equilibrium isotherms were determined at optimum temperature and pH to characterize the sorption process. Statistical parameters such as mass transfer coefficients, multiple regression analysis were applied to establish the mechanism. It is suggested that the characterization of suitable, and exhausted sorbent through the application of fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF) is essential to establish its surface bonding. Scope for safety evaluation and risk assessment to human and biosphere may provide the guideline and predication to the regulatory agencies for its sustainable use and safe disposal The ecotoxicological assessment of the leachates and low cost removal technology are discussed in this paper.     

Bactericidal properties of natural and synthetic sea water as influenced by addition of low amounts of organic matter

The influence of added organic nutrients on the bactericidal capacity of natural and synthetic sea water was investigated, with special reference to levels below the normal concentration of orgnnic matter in natural sea water. Resting cells of Escherichia coli, Staphylococcus aureus and Serratia marinorubra were used as test organisms. The inactivation of test bacteria in synthetic and filter-sterilized natural sea water could be increased by addition of ZoBell's 2216E-broth (containing peptone and yeast extract), peptone or glucose. This effect of the nutrients depended on chemical nature and concentration as well as on specific properties of the test strains. In regard to peptone, less than 10^-4 mg/ml must be added to induce bacterial kill exceeding that observed with unsupplemented controls. With raw sea water, no fundamentally different results were obtained; however, the influence of marine bacteria was clearly discernible. All findings support a previously offered hypothesis of nutrient-dependent antibacterial activity of sea water which is discussed in detail.     

Magnetic particles precipitated onto wheat husk for removal of methyl blue from aqueous solution

Magnetic particles prepared via co-precipitation and impregnated onto wheat husk (MN-WH) were used for the removal of methyl blue (MB) from aqueous solution. Experiments were conducted in a batch mode for optimization regarding pH, contact time, adsorbent dose, initial dye concentrations, and temperature. Maximum adsorption (98%) was achieved at pH 5. The adsorption data were fitted into pseudo-first, pseudo-second, intraparticle diffusion, and Elovich equation revealing that adsorption followed pseudo-second-order kinetics. The four most common isotherm models, i.e. the Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich (D–R), were used to evaluate the data, with the best fit to a Langmuir isotherm (R² = 0.996), followed by a Freundlich isotherm (R² = 0.995), indicating monolayer adsorption of MB on the surface of MN-WH. Thermodynamic parameters calculated from the Van't Hoff equation revealed that the adsorption is exothermic (ΔHº = ?19.7 kJ mol^?1).     

快速评估近岸海洋水体与沉积物中E.coli与S.aureus抗生素抗性水平的新方法

随着抗生素抗性污染日益严重,快速评估环境中典型病原菌与条件性致病菌的抗生素抗性水平,对掌握区域环境抗生素抗性污染状况、揭示抗性污染传播规律至关重要。通过以最低抑菌浓度浸入抗生素改进MI、VJ培养基,并结合滤膜法,建立了针对近岸海洋环境中指示性病原微生物大肠杆菌(Escherichia coli,E.coli)与金黄色葡萄球菌(Staphylococcus aureus,S.aureus)的抗生素抗性监测方法。水体和沉积物样品抗生素抗性水平评估实验结果显示,该方法具有较好重现性(水体和沉积物中E.coli和S.aureus抗生素抗性水平的相对标准偏差分别为11%、8%)与准确度(水体和沉积物中E.coli和S.aureus的平均回收率分别为83.5%、68.4%;相对于CLSI药敏试验的偏离度为±0.1)。且与CLSI药敏实验相比,该方法过程简便、耗时短(36 h/84 h),能最大限度节约经济和人员成本提高抗性评价效率。应用该方法评估辽河口与莱州湾环境中2种病原微生物磺胺类抗生素抗性水平,结果显示辽河口水体中E.coli和S.aureus磺胺二甲嘧啶的平均抗性率分别为27.0%、28.4%,沉积物中分别为35.5%、34.6%;莱州湾水体中E.coli和S.aureus磺胺二甲嘧啶的平均抗性率分别为26.0%、14.5%,沉积物中分别为12.0%、32.9%。该方法适用于河口、近岸海洋及入海排污口水体与沉积物样品中E.coli与S.aureus的快速分析及抗生素抗性水平评估。     

Effect of ultraviolet irradiation and chlorination on ampicillin-resistant <Emphasis Type="Italic">Escherichia coli</Emphasis> and its ampicillin resistance gene

Antibiotic resistance is a serious public health risk that may spread via potable and reclaimed water. Effective disinfection is important for inactivation of antibiotic-resistant bacteria and disruption of antibiotic resistance genes. Ampicillin is a widely prescribed antibiotic but its effectiveness is increasingly undermined by resistance. In this study, changes in ampicillin resistance for Escherichia coli (E. coli) CGMCC 1.1595 were analyzed after exposure to different doses of ultraviolet (UV) or chlorine, and damage incurred by the plasmid encoding ampicillin resistance gene bla _TEM-1 was assessed. We reported a greater stability in ampicillinresistant E. coli CGMCC 1.1595 after UV irradiation or chlorination when compared with previously published data for other E. coli strains. UV irradiation and chlorination led to a shift in the mortality frequency distributions of ampicillin-resistant E. coli when subsequently exposed to ampicillin. The ampicillin hemiinhibitory concentration (IC₅₀) without disinfection was 3800 mg·L^–1, and an increment was observed after UV irradiation or chlorination. The IC₅₀ of ampicillin-resistant E. coli was 1.5-fold higher at a UV dose of 40 mJ·cm^–2, and was 1.4-fold higher when exposed to 2.0 mg·L^–1 chlorine. These results indicate that UV irradiation and chlorination can potentially increase the risk of selection for E. coli strains with high ampicillin resistance. There was no evident damage to bla _TEM-1 after 1–10 mg Cl₂·L^–1 chlorination, while a UV dose of 80 mJ·cm^–2 yielded a damage ratio for bla _TEM-1 of approximately 1.2-log. Therefore, high UV doses are required for effective disruption of antibiotic resistance genes in bacteria.     

Human risk assessment of As,Cd, Cu and Zn in the abandoned metal mine site

The cancer risk and the non-cancer hazard index for inhabitants exposed to As, Cd, Cu and Zn in the soils and stream waters of the abandoned Songcheon Au–Ag mine area were evaluated. Mean concentrations of As, Cd, Cu, Pb and Zn in agricultural soils were 230, 2.5, 120, 160, and 164 mg kg⁻¹, respectively. Mean concentrations of As, Cd and Zn of the water in the stream where drinking water was drawn was 246 μg L⁻¹, 161 μg L⁻¹ and 3899 μg L⁻¹, respectively. These levels are significantly higher than the permissible levels for drinking water quality recommended by Korea and WHO. The resulting human health risks to farmers who inhabited the surrounding areas due to drinking water were summarized as follows: (1) the non-cancer health hazard indices showed that the toxic risk due to As and Cd in drinking water were 10 and 4 times, respectively, greater than those induced by the safe average daily dosages of the respective chemicals. (2) the cancer risk of As for exposed individuals through the drinking water pathway was 5 in 1000, exceeded the acceptable risk of 1 in 10,000 set for regulatory purposes.