Metal-containing landfills as a source of antibiotic tolerance.

To unveil the potential effect of metal presence to antibiotic tolerance proliferation, four sites of surface landfills containing tailings from metal processing in Slovakia (Hnústa, Hodrusa, Kosice) and Poland (Tarnowskie Góry) were investigated. Tolerance and multitolerance to selected metals (Cu, Ni, Pb, Fe, Zn, Cd) and antibiotics (ampicillin, tetracycline, chloramphenicol, and kanamycin) and interrelationships between them were evaluated. A low bacterial diversity (Shannon-Wiener index from 0.83 to 2.263) was detected in all sampling sites. Gram-positive bacteria, mostly belonging to the phylum Actinobacteria, dominated in three of the four sampling sites. The recorded percentages of tolerant bacterial isolates varied considerably for antibiotics and metals from 0 to 57% and 0.8 to 47%, respectively, among the sampling sites. Tolerances to chloramphenicol (45-57%) and kanamycin (32-45%) were found in three sites. Multitolerance to several metals and antibiotics in the range of 24 to 48% was recorded for three sites. A significant positive correlation (p < 0.05) for the co-occurrence of tolerance to each studied metal and at least one of the antibiotics was observed. Exposure time to the metal (landfill duration) was an important factor for the development of metal- as well as antibiotic-tolerant isolates. The results show that metal-contaminated sites represent a significant threat for human health not only for their toxic effects but also for their pressure to antibiotic tolerance spread in the environment.

Effect of chloramphenicol on the life table demography of Brachionus calyciflorus (Rotifera): A multigenerational study.

During the last two decades, there has been increasing concerns about the presence of antibiotics in aquatic environments. Phenicol antibiotics, such as chloramphenicol (CMP), commonly used in the veterinary and aquaculture fields to treat infections, have been often detected in aquatic environments, but scarce ecotoxicity information regarding the effects of CMP on non-target aquatic organisms is available, and multigenerational studies are seldom studied. Here we quantified the demographic responses of Brachionus calyciflorus exposed to sublethal concentrations (0, 5, 10, 30, 50, 70 and 90 mg L-1) of CMP for three successive generations (P0, F1, and F2). Our results showed that compared to the control, higher concentrations of CMP significantly decreased the life expectancy at hatching, generation time, net reproductive rate and intrinsic rate of population increase in all three generations, and the proportion of mictic offspring in the F1 generation of B. calyciflorus. With increasing generations, higher concentrations of CMP showed increased toxic effects on life expectancy at hatching and net reproductive rate, but irregular negative effects on generation time, intrinsic rate of population increase, and proportion of mictic offspring of the rotifers. These results indicate that multigenerational studies are necessary to prevent insufficient assessments of the impact of antibiotics in aquatic ecosystems.

How to disinfect anuran eggs? Sensitivity of anuran embryos to chemicals widely used for the disinfection of larval and post-metamorphic amphibians.

Emerging infectious diseases are major drivers of global and local amphibian biodiversity loss. Therefore, developing effective disinfection methods to manage the impact of diseases in wild and captive "ark" populations are an important goal in amphibian conservation. While chemical disinfectants have been used safely and effectively in larval and adult amphibians infected with pathogenic microbes, their applicability to amphibian egg masses has remained untested. To bridge this gap, we exposed embryos of the common toad (Bufo bufo) and agile frog (Rana dalmatina) experimentally to three widely used disinfectants: voriconazole, chloramphenicol and chlorogen-sesquihydrate. For 3 days we exposed portions of egg masses to these disinfectants at 1×, 2×, 5× and 10× the concentration recommended for the disinfection of tadpoles and adults. Subsequently, we recorded embryonic and larval survival, as well as larval body mass and the incidence of abnormalities 12 days after hatching. Application of voriconazole had species- and concentration-dependent negative impacts on survival and body mass, and caused marked malformations in the viscerocranial structure of B. bufo tadpoles. Exposure to chlorogen-sesquihydrate also resulted in significant mortality in B. bufo embryos and negatively affected body mass of R. dalmatina larvae. Chloramphenicol had little negative effects on embryos or larvae in either species. Based on these results, the application of voriconazole and chlorogen-sesquihydrate cannot be recommended for the disinfection of amphibian eggs, whereas treatment with chloramphenicol appears to be a safe method for eliminating potential pathogens from anuran egg masses and their immediate aquatic environment.

Mixture toxicity effects of chloramphenicol, thiamphenicol, florfenicol in Daphnia magna under different temperatures.

Acute toxicities of chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FLO) and their mixtures on Daphnia magna under two representative temperatures of the aquatic environment (20 and 25 °C) have been examined. Their toxicities depicted with an order of 72-h EC50 values were as follows: CAP > FLO > TAP and CAP ≈ FLO > TAP under 20 and 25 °C, separately. Furthermore, the acute toxicity significantly increased with the rise of temperature from 20 to 25 °C in nearly all separate and mixture phenicol antibiotics. Meanwhile, the most toxic combination under two different temperatures was diverse. The nature of toxicological interactions of phenicol antibiotic mixtures was analyzed by Combination Index (CI) equation. In general, a dual synergism-antagonism effect was dominant in nearly all mixtures at both temperatures. The prediction suitability of Concentration Addition (CA), Independent Action (IA) models, and CI method was compared, suggesting that the CI equation seems to be more appropriate for predicting the toxicity values of phenicol drugs than CA and IA models. In brief, phenicol antibiotic mixtures with temperature variation may pose more significant hazards and risks to aquatic organisms; hence, the environment.

The Influence of Metabolic Inhibitors, Antibiotics, and Microgravity on Intact Cell MALDI-TOF Mass Spectra of the Cyanobacterium Synechococcus Sp. UPOC S4.

The aim and novelty of this paper are found in assessing the influence of inhibitors and antibiotics on intact cell MALDI-TOF mass spectra of the cyanobacterium Synechococcus sp. UPOC S4 and to check the impact on reliability of identification. Defining the limits of this method is important for its use in biology and applied science. The compounds included inhibitors of respiration, glycolysis, citrate cycle, and proteosynthesis. They were used at 1-10 µM concentrations and different periods of up to 3 weeks. Cells were also grown without inhibitors in a microgravity because of expected strong effects. Mass spectra were evaluated using controls and interpreted in terms of differential peaks and their assignment to protein sequences by mass. Antibiotics, azide, and bromopyruvate had the greatest impact. The spectral patterns were markedly altered after a prolonged incubation at higher concentrations, which precluded identification in the database of reference spectra. The incubation in microgravity showed a similar effect. These differences were evident in dendrograms constructed from the spectral data. Enzyme inhibitors affected the spectra to a smaller extent. This study shows that only a long-term presence of antibiotics and strong metabolic inhibitors in the medium at 10-5 M concentrations hinders the correct identification of cyanobacteria by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF).

Growth and Cellular Responses of Toxigenic Microcystis to Chloramphenicol-Stress at Various Environmentally-Relevant Nitrogen Levels.

This study explored nitrogen (N)-dependent interaction between Microcystis and chloramphenicol (CAP) along 20 day-test. Results showed that 5 mg/L N largely alleviated inhibitory effects of CAP on Microcystis growth, while 50 and 0.5 mg/L N exacerbated growth-inhibition by CAP especially in early (before day 8) and mid-late stage, respectively. At each N level, CAP-induced antioxidant defense and cell damage extents were negatively correlated to growth state in each stage, and CAP-biodegradation coincided with Microcystis growth and glutathione synthesis dynamics, implying that antioxidant defense, cell damage and CAP-removal closely linked to N-dependent Microcystis growth under CAP-stress. Microcystin (MC)-production and -release under CAP-stress were also N-dependent. Although Microcystis growth was greatly-inhibited by prolonged CAP-stress at 0.5 mg/L N, delayed CAP-loss and high MC-release at 0.5 mg/L N should be emphasized during Microcystis-dominated cyanobacterial blooms (MCBs) and CAP co-occurrence. This study had great implication in risk assessment for MCBs-CAP co-occurrence in different waters.

Phosphorus Influences the Interaction Between Toxigenic Microcystis and Chloramphenicol.

Microcystis growth and physiological responses to chloramphenicol (CAP)-stress were explored at different phosphorus (P) concentrations during 20-day exposure. Under CAP-stress, Microcystis exhibited (i) stronger total protein synthesis and antioxidant defenses at 5 mg/L P than 0.05-0.5 mg/L P in early test period (before day 8), and (ii) greater CAP-removal via biodegradation at 5 mg/L P in mid-late period. Due to above mechanisms, 5 mg/L P largely alleviated the inhibitory effect of CAP on Microcystis growth until test end, thus minimizing CAP toxicity to Microcystis, compared with 0.05-0.5 mg/L P. Moreover, microcystin-production and -release by Microcystis under CAP-stress were also P-dependent. These results suggested that under CAP-stress, although Microcystis growth was more inhibited at 0.05-0.5 mg/L P, higher microcystin-release and CAP residual at 0.05-0.5 mg/L P than at 5 mg/L P still caused eco-risks, which had important implication for risk assessment during Microcystis-dominated blooms and CAP pollution co-occurrence in different waters.

Classification of Cholestatic and Necrotic Hepatotoxicants Using Transcriptomics on Human Precision-Cut Liver Slices.

Human toxicity screening is an important stage in the development of safe drug candidates. Hepatotoxicity is one of the major reasons for the withdrawal of drugs from the market because the liver is the major organ involved in drug metabolism, and it can generate toxic metabolites. There is a need to screen molecules for drug-induced hepatotoxicity in humans at an earlier stage. Transcriptomics is a technique widely used to screen molecules for toxicity and to unravel toxicity mechanisms. To date, the majority of such studies were performed using animals or animal cells, with concomitant difficulty in interpretation due to species differences, or in human hepatoma cell lines or cultured hepatocytes, suffering from the lack of physiological expression of enzymes and transporters and lack of nonparenchymal cells. The aim of this study was to classify known hepatotoxicants on their phenotype of toxicity in humans using gene expression profiles ex vivo in human precision-cut liver slices (PCLS). Hepatotoxicants known to induce either necrosis (n = 5) or cholestasis (n = 5) were used at concentrations inducing low (<30%) and medium (30-50%) cytotoxicity, based on ATP content. Random forest and support vector machine algorithms were used to classify hepatotoxicants using a leave-one-compound-out cross-validation method. Optimized biomarker sets were compared to derive a consensus list of markers. Classification correctly predicted the toxicity phenotype with an accuracy of 70-80%. The classification is slightly better for the low than for the medium cytotoxicity. The consensus list of markers includes endoplasmic reticulum stress genes, such as C2ORF30, DNAJB9, DNAJC12, SRP72, TMED7, and UBA5, and a sodium/bile acid cotransporter (SLC10A7). This study shows that human PCLS are a useful model to predict the phenotype of drug-induced hepatotoxicity. Additional compounds should be included to confirm the consensus list of markers, which could then be used to develop a biomarker PCR-array for hepatotoxicity screening.

Conjugation with polyamines enhances the antibacterial and anticancer activity of chloramphenicol.

Chloramphenicol (CAM) is a broad-spectrum antibiotic, limited to occasional only use in developed countries because of its potential toxicity. To explore the influence of polyamines on the uptake and activity of CAM into cells, a series of polyamine-CAM conjugates were synthesized. Both polyamine architecture and the position of CAM-scaffold substitution were crucial in augmenting the antibacterial and anticancer potency of the synthesized conjugates. Compounds 4 and 5, prepared by replacement of dichloro-acetyl group of CAM with succinic acid attached to N4 and N1 positions of N(8),N(8)-dibenzylspermidine, respectively, exhibited higher activity than CAM in inhibiting the puromycin reaction in a bacterial cell-free system. Kinetic and footprinting analysis revealed that whereas the CAM-scaffold preserved its role in competing with the binding of aminoacyl-tRNA 3'-terminus to ribosomal A-site, the polyamine-tail could interfere with the rotatory motion of aminoacyl-tRNA 3'-terminus toward the P-site. Compared to CAM, compounds 4 and 5 exhibited comparable or improved antibacterial activity, particularly against CAM-resistant strains. Compound 4 also possessed enhanced toxicity against human cancer cells, and lower toxicity against healthy human cells. Thus, the designed conjugates proved to be suitable tools in investigating the ribosomal catalytic center plasticity and some of them exhibited greater efficacy than CAM itself.

Photocatalytic degradation of the antibiotic chloramphenicol and effluent toxicity effects.

Chloramphenicol sodium succinate (CAP, C15H15Cl2N2 Na2O8) is a broad-spectrum antibiotic exhibiting activity against both Gram-positive and Gram-negative bacteria as well as other groups of microorganisms only partially removed by conventional activated sludge wastewater treatment plants. Thus, CAP and its metabolites can be found in effluents. The present work deals with the photocatalytic degradation of CAP using TiO2 as photocatalyst. We investigated the optimization of reaction contact time and concentration of TiO2 considering CAP and its by-products removal as well as effluent ecotoxicity elimination. Considering a CAP real concentration of 25mgL(-1), kinetic degradation curves were determined at 0.1, 0.2, 0.4, 0.8, 1.6 and 3.2gL(-1) TiO2 after 5, 10, 30, 60 and 120min reaction time. Treated samples were checked for the presence of by-products and residual toxicity (V. fischeri, P. subcapitata, L. sativum and D. magna). Results evidenced that the best combination for CAP and its by-products removal could be set at 1.6gL(-1) of TiO2 for 120min with an average residual toxicity of approximately 10%, that is the threshold set for negative controls in most toxicity tests for blank and general toxicity test acceptability.

Phytotoxicity of veterinary antibiotics to seed germination and root elongation of crops.

Large quantities of veterinary antibiotics (VAs) are being used worldwide in agricultural fields through wastewater irrigation and manure application. They cause damages to the ecosystem when discharged into the environment, but there is a lack of information on their toxicity to plants and animals. This study evaluated the phytotoxic effects of five major VAs, namely tetracycline (TC), sulfamethazine (SMZ), norfloxacin (NOR), erythromycin (ERY) and chloramphenicol (CAP), on seed germination and root elongation in lettuce, tomato, carrot and cucumber, and investigated the relationship between their physicochemical properties and phytotoxicities. Results show that these compounds significantly inhibited root elongation (p<0.05), the most sensitive endpoint for the phytotoxicity test. TC was associated with the highest level of toxicity, followed by NOR, ERY, SMZ and CAP. Regarding crop species, lettuce was found to be sensitive to most of the VAs. The median effect concentration (EC50) of TC, SMZ, NOR, ERY and CAP to lettuce was 14.4, 157, 49.4, 68.8 and 204 mg/L, respectively. A quantitative structure-activity relationship (QSAR) model has been established based on the measured data. It is evident that hydrophobicity was the most important factor governing the phytotoxicity of these compounds to seeds, which could be explained by the polar narcosis mechanism. Lettuce is considered a good biomarker for VAs in the environment. According to the derived equation, phytotoxicities of selected VA compounds on different crops can be calculated, which could be applicable to other VAs. Environmental risks of VAs were summarized based on the phytotoxicity results and other persistent factors.

Assessment of health risks resulting from early-life exposures: Are current chemical toxicity testing protocols and risk assessment methods adequate?

Abstract Over the last couple of decades, the awareness of the potential health impacts associated with early-life exposures has increased. Global regulatory approaches to chemical risk assessment are intended to be protective for the diverse human population including all life stages. However, questions persist as to whether the current testing approaches and risk assessment methodologies are adequately protective for infants and children. Here, we review physiological and developmental differences that may result in differential sensitivity associated with early-life exposures. It is clear that sensitivity to chemical exposures during early-life can be similar, higher, or lower than that of adults, and can change quickly within a short developmental timeframe. Moreover, age-related exposure differences provide an important consideration for overall susceptibility. Differential sensitivity associated with a life stage can reflect the toxicokinetic handling of a xenobiotic exposure, the toxicodynamic response, or both. Each of these is illustrated with chemical-specific examples. The adequacy of current testing protocols, proposed new tools, and risk assessment methods for systemic noncancer endpoints are reviewed in light of the potential for differential risk to infants and young children.

Effect of organic toxicants on the activity of denitrifying granular sludge.

Denitrification plays a key role in the biological nitrogen removal from the wastewater using granular sludge as the integral part of a high-rate denitrification technology. It is helpful to evaluate the effect of typical organic toxicants on the activity of denitrifying granular sludge for the application of denitrification technology. In this study, four typical organic toxicants, namely, penicillin, chloramphenicol, 2,4-dinitrophenol and polymyxin B sulphate were used to assess the effect of organic toxicants on the activity of denitrifying granular sludge. The results of individual toxicity indicated that penicillin, chloramphenicol and 2,4-dinitrophenol had significant inhibition, whose half-inhibitory concentrations were 0.534, 0.162 and 0.474 g/L with respective inhibitory magnitudes of 90.79%/(g/L), 282.5%/(g/L) and 138.83%/(g/L). Polymyxin B sulphate showed no significant inhibition. The results of combined toxicity indicated that the binary mixture of penicillin and chloramphenicol had an antagonistic effect, both the binary mixture of penicillin and 2,4-dinitrophenol and the binary mixture of chloramphenicol and 2,4-dinitrophenol had additive effects. The ternary mixture of penicillin, chloramphenicol and 2,4-dinitrophenol had a partial additive effect.

Predicting the long-term toxicity of five-antibiotic mixtures to Vibrio qinghaiensis sp. Q67.

Concentration addition (CA) is commonly used as a standard additive reference model to predict the short-term toxicity for most chemical mixtures. Whether CA can predict the long-term toxicity of antibiotic mixtures was investigated. The long-term toxicity of five antibiotics including apramycin sulfate, paromomycin sulfate, tetracycline hydrochloride, chloramphenicol and streptomycin sulfate and their mixtures to a photo bacterium Q67 were detected by the long-term toxicity microplate analysis procedure. Seven five-antibiotic mixtures with various concentration ratios and concentration levels were designed by employing uniform design ray method. The long-term mixture toxicity was predicted by CA based on the toxicity data of single antibiotics. The results showed that Weibull or Logit function fit well with the long-term toxicity data of all the components and their mixtures (R>0.98 and RMSE<0.07). According the toxicity index, the negative logarithm of mean effect concentration, the long-term toxicity of the five antibiotics differs greatly and is higher than their short-term toxicity. The predicted values by CA model conformed to the experimental values of mixtures, which implies CA can predict reliable results for the long-term toxicity of antibiotic mixtures.

Integrative chemical-biological read-across approach for chemical hazard classification.

Traditional read-across approaches typically rely on the chemical similarity principle to predict chemical toxicity; however, the accuracy of such predictions is often inadequate due to the underlying complex mechanisms of toxicity. Here, we report on the development of a hazard classification and visualization method that draws upon both chemical structural similarity and comparisons of biological responses to chemicals measured in multiple short-term assays ("biological" similarity). The Chemical-Biological Read-Across (CBRA) approach infers each compound's toxicity from both chemical and biological analogues whose similarities are determined by the Tanimoto coefficient. Classification accuracy of CBRA was compared to that of classical RA and other methods using chemical descriptors alone or in combination with biological data. Different types of adverse effects (hepatotoxicity, hepatocarcinogenicity, mutagenicity, and acute lethality) were classified using several biological data types (gene expression profiling and cytotoxicity screening). CBRA-based hazard classification exhibited consistently high external classification accuracy and applicability to diverse chemicals. Transparency of the CBRA approach is aided by the use of radial plots that show the relative contribution of analogous chemical and biological neighbors. Identification of both chemical and biological features that give rise to the high accuracy of CBRA-based toxicity prediction facilitates mechanistic interpretation of the models.

Response of bacterial isolates from Antarctic shallow sediments towards heavy metals, antibiotics and polychlorinated biphenyls.

The response of bacterial isolates from Antarctic sediments to polychlorinated biphenyls (Aroclor 1242 mixture), heavy metal salts (cadmium, copper, mercury and zinc) and antibiotics (ampicillin, chloramphenicol, kanamycin and streptomycin) was investigated. Overall, the ability to growth in the presence of Aroclor 1242 as a sole carbon source was observed for 22 isolates that mainly belonged to Psychrobacter spp. Tolerance to the heavy metals assayed in this study was in the order of Cd > Cu > Zn > Hg and appeared to be strictly related to the metal concentrations, as determined during previous chemical surveys in the same area. With regards to antibiotic assays, the response of the isolates to the tested antibiotics ranged from complete resistance to total susceptibility. In particular, resistances to ampicillin and chloramphenicol were very pronounced in the majority of isolates. Our isolates differently responded to the presence of toxic compounds primarily based on their phylogenetic affiliation and secondarily at strain level. Moreover, the high incidence of resistance either to metal or antibiotics, in addition to the capability to grow on PCBs, confirm that bacteria are able to cope and/or adapt to the occurrence pollutants even in low human-impacted environments.

Acute and chronic toxic effects of chloramphenicol on Scenedesmus obliquus and Chlorella pyrenoidosa.

The acute and chronic toxicological effects of Chloramphenicol (CAP) on Scenedesmus obliquus and Chlorella pyrenoidosa are not well understood. The indoor experiments were carried to observe and analyze the CAP induced changes. Results of the observations have showed that CAP exposure could significantly inhibit the growth of Scenedesmus obliquus in almost all the treated groups, while Chlorella pyrenoidosa exhibited less sensitivity. Chlorophyll-a syntheses of Scenedesmus obliquus were all inhibited by CAP exposure, while Chlorella pyrenoidosa displayed obvious stimulation effect. Catalase (CAT) and Superoxide dismutase (SOD) activities of both algae were promoted in all the treatments. The experimental results indicated that the growth and Chlorophyll-a syntheses of Scenedesmus obliquus were more sensitive in response to CAP exposure than that of Chlorella pyrenoidosa. While for CAT and SOD activities, Chlorella pyrenoidosa showed more susceptible. This research provides a basic understanding of CAP toxicity to aquatic organisms.

Three-dimensional graphene aerogel mitigated the toxic impact of chloramphenicol wastewater on microorganisms in an EGSB reactor.

Anaerobic treatment of chloramphenicol wastewater holds significant promise due to its potential for bioenergy generation. However, the high concentration of organic matter and residual toxic substances in the wastewater severely inhibit the activity of microorganisms. In this study, a three-dimensional graphene aerogel (GA), as a conductive material with high specific surface area (114.942 m2 g-1) and pore volume (0.352 cm3 g-1), was synthesized and its role in the efficiency and related mechanism for EGSB reactor to treat chloramphenicol wastewater was verified. The results indicated that synergy effects of GA for Chemical Oxygen Demand (COD) removal (increased by 8.17 %), chloramphenicol (CAP) removal (increased by 4.43 %) and methane production (increased by 70.29 %). Furthermore, GA increased the average particle size of anaerobic granular sludge (AGS) and promoted AGS to secrete more redox active substances. Microbial community analysis revealed that GA increased the relative abundance of functional bacteria and archaea, specifically Syntrophomonas, Geobacter, Methanothrix, and Methanolinea. These microbial species can participate in direct interspecific electron transfer (DIET). This research serves as a theoretical foundation for the application of GA in mitigating the toxic impact of refractory organic substances, such as antibiotics, on microorganisms during anaerobic treatment processes.

Effects of natural nanoparticles on the acute toxicity, chronic effect, and oxidative stress response of phenicol antibiotics in Daphnia magna.

Natural nanoparticles (NNP) are ubiquitous in natural water and can interact with other contaminants, causing ecotoxic effects on aquatic nontarget organisms. However, the impact of NNPs on the ecotoxicity of antibiotics remains largely unknown. This work investigated the acute toxicity, chronic effect, and oxidative response and damage in Daphnia magna co-exposed to phenicol antibiotics (chloramphenicol, thiamphenicol) and different concentrations of NNPs (10 mg/L: environmentally relevant concentration; 100 mg/L: a high concentration that caused no apparent immobilization in D. magna). The results showed that the acute toxicity of chloramphenicol was increased by 10 mg/L NNPs but decreased by 100 mg/L NNPs; both concentrations of NNPs increased and decreased acute toxicities of thiamphenicol and chloramphenicol + thiamphenicol treatments, respectively. After long-term exposure, phenicol antibiotics (1 µg/L) and NNP (10 mg/L) mixtures in environmentally relevant concentrations significantly affected the reproduction of D. magna but did not influence their growth. The catalase activity, reduced glutathione level, and malonaldehyde content in D. magna also varied with the NNPs concentrations. Notably, the lowest concentration of thiamphenicol and chloramphenicol + thiamphenicol combined with NNPs significantly increased the malondialdehyde content in D. magna compared with the control, indicating membrane lipid peroxidation occurred in daphnids. This study suggests that the toxic effects of contaminants and NNPs on aquatic organisms should be considered thoroughly to avoid underestimating the hazard of these pollutants in the actual aquatic environment.

Simultaneous removal of norfloxacin and chloramphenicol using cold atmospheric plasma jet (CAPJ): Enhanced performance, synergistic effect, plasma-activated water (PAW) contribution, mechanism and toxicity evaluation.

The extensive abuse and inadvertent discharge of various antibiotics into the environment has become a serious problem for posing a big threat to human health. In order to deal with this problem, we utilized cold atmospheric plasma jet (CAPJ) to treat two different antibiotics, namely, norfloxacin and chloramphenicol, and investigated the efficiencies and corresponding mechanisms for removing the mixed antibiotics. In the application of the CAPJ technique, we made use of not only the direct plasma processing, but also the indirect plasma-activated water (PAW) treatment. The efficiency for mixed antibiotics treatment was considerably enhanced as compared to the efficiency for treatment of single antibiotics. The contributions from the CAPJ-induced reactive oxygen/nitrogen species (RONS) were examined, showing that ·OH and 1O2 played a major role in the degradation of norfloxacin and chloramphenicol in the direct plasma treatment, while 1O2 played a major role in the PAW treatment. The bio-toxicity evaluation was also provided to verify the ecological safety of the CAPJ treatment. As such, this work has not only showed the effectiveness of CAPJ treatment of mixed antibiotics, but also elucidated the mechanisms for the enhanced treatment efficiency, which may provide a new solution for treatment of antibiotics in the environment.