The two faces of antibiotics: an overview of the effects of antibiotic residues in foodstuffs.

Antibiotics, which have been used for many years to treat infections, also play an important role in food contamination with antibiotic residues. There is also unnecessary use of antibiotics, particularly to increase production efficiency. Non-compliance with withdrawal periods and maximum residue limits (MRLs) for antibiotics used in food-producing animals results in undesirable events, such as allergic reactions, teratogenicity, carcinogenicity, changes in the microbiota and, in particular, antibiotic resistance. Therefore, it may be useful to avoid unnecessary use of antibiotics, to limit the use of antibiotics and to turn to alternatives that can be used instead of antibiotics. The aim of this review is to provide information on the undesirable effects of antibiotic residues in food-producing organisms and in the environment, their determination, and the precautions that can be taken.

Genotoxicity of selected pharmaceuticals, their binary mixtures, and varying environmental conditions - study with human adenocarcinoma cancer HT29 cell line.

Pharmaceutical residues are present in the environment in mixtures and their adverse effects may also result from interactions that occur between compounds. Studies presented in this work focus on genotoxicity of pharmaceuticals from different therapeutic groups in mixtures and in individual solutions impacted with different environmental conditions assessed using comet assay (alkaline approach). Binary mixtures of pharmaceuticals (in different concentration ratios) and in individual solutions impacted with pH change (range from 5.5 to 8.5) or addition of inorganic ions, were incubated with HT29 cells and after 24 h time period cells were tested for the presence of DNA damage. To estimate whether mixtures act more (synergistic) or less (antagonistic) efficiently Concentrations Addition (CA) and Independent Action (IA) approaches were applied followed by a calculation of the Model Deviation Ratio (MDR) to determine deviation from the predicted values. Addition of inorganic ions mainly reduced their genotoxicity. Diclofenac s. was the most susceptible to potassium, fluoride, and bromide ions. Change of the pH of pharmaceutical solutions had significant impact on genotoxicity of diclofenac s. and fluoxetine h. Among mixtures, more commonly observed interactions were synergistic ones, exactly twenty-five cases (ten pairs containing chloramphenicol or oxytetracycline h.) and ten cases of antagonism (four for pairs containing chloramphenicol or fluoxetine h.). The results obtained indicate that interactions between tested compounds occur frequently and can lead to DNA damage. This topic especially concerning in vitro tests using cells is still rare, however, it should not be neglected.

Occurrence and potential human health risk of pharmaceutical residues in drinking water from Putrajaya (Malaysia).

Occurrence of pharmaceutical residues in drinking water has been widely reported in countries that have registered steady economic growth. This can exert concerns among the general consumers, prompting them to explore the potential human health risks associated with continuous exposure to pharmaceuticals. However, such an occurrence is rarely reported in developing or under-developed countries. To give more contexts, this study looked at the presence of nine pharmaceutical residues in drinking water (amoxicillin, caffeine, chloramphenicol, ciprofloxacin, dexamethasone, diclofenac, nitrofurazone, sulfamethoxazole, and triclosan) at Putrajaya residential area in Malaysia. Additionally, the potential health risks associated with contaminated drinking water were investigated. This study has found the presence of pharmaceutical residue concentrations up to 0.38 ng/L, with the highest concentration of caffeine (0.38 ng/L) and the lowest concentration of diclofenac (0.14 ng/L). In comparison, all the nine pharmaceutical residues were substantially lower than previously reported studies. In general, Hazard Quotient (HQ) values indicated that low potential health hazards were present for all age groups. Nevertheless, quantitative occurrences of pharmaceutical residues in drinking water will help guide future toxicological studies to examine other chronic effects, while canvassing for proper framework to look into the water risk management and regulation in Malaysia.

Nonmedical Uses of Antibiotics: Time to Restrict Their Use?

The global crisis of antibiotic resistance has reached a point where, if action is not taken, human medicine will enter a postantibiotic world and simple injuries could once again be life threatening. New antibiotics are needed urgently, but better use of existing agents is just as important. More appropriate use of antibiotics in medicine is vital, but the extensive use of antibiotics outside medical settings is often overlooked. Antibiotics are commonly used in animal husbandry, bee-keeping, fish farming and other forms of aquaculture, ethanol production, horticulture, antifouling paints, food preservation, and domestically. This provides multiple opportunities for the selection and spread of antibiotic-resistant bacteria. Given the current crisis, it is vital that the nonmedical use of antibiotics is critically examined and that any nonessential use halted.

Sublethal chronic effects of oral dietary exposure to deltamethrin in Swiss albino mice.

The hazards of dietary exposure to environmentally relevant levels of deltamethrin are poorly understood though studies enunciate the acute toxicity hazards. In this study, prolonged exposure to low levels of deltamethrin in mice was investigated. The mice were exposed daily via gavage method for 60 days. Four doses (0.1, 0.05, 0.01, and 0.005 mg/kg bwt/d) were selected, which are equal to or less than the maximum residue limits for deltamethrin permitted in animal food/feed. Liver, kidney, lungs, spleen, and testes were collected on day 61 for histology, residue, and biochemical analysis (aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALKP), total bilirubin (TBIL), total proteins (TPs), cholesterol (CHOL), urea, and creatinine). No significant changes were observed in body weight gain in all treatment groups ( p > 0.05). The gas chromatography analysis indicated that none of the tissue samples contained deltamethrin residues above the limits of quantification. The significant differences in biochemical profile (AST, ALT, TBIL, and creatinine) reported in animals exposed to 0.1 and 0.05 mg/kg bwt/d deltamethrin ( p < 0.05) suggest respective tissue injury and lipid peroxidation; however, few significant changes in urea and CHOL were also reported in doses 0.01 and 0.005 mg/kg bwt. No significant differences in TP and ALKP were observed ( p > 0.05). The target organs for deltamethrin toxicity showed prominent histopathological changes in concentrations of 0.1 and 0.05 mg/kg bwt. Other two doses showed no or sporadic changes. Our findings suggest that chronic exposure to environmentally relevant levels of deltamethrin can have detrimental effects on vital organs in the circumstances allowing daily exposure, in congruence with available literature.

Residual ethylene glycol and dimethyl sulphoxide concentration in human ovarian tissue during warming/thawing steps following cryopreservation.

There have been 60 births after transplantation of cryopreserved ovarian tissue: 58 using the slow freezing method, and two using the vitrification method. DMSO and EG are widely used as cryoprotectants. However DMSO is a known epimutagen, and EG has been reported to be toxic in high concentrations. In this study, we measured residual DMSO and EG in ovarian tissue after vitrification and slow freezing. Cryoprotectants remained at a high concentration in the vitrified/warmed ovarian tissue just before transplantation (DMSO: 9.8 mg/g, EG: 9.8 mg/g). We must consider the impact of the cryoprotectants on the mother and the baby.

Exploring Post-Treatment Reversion of Antimicrobial Resistance in Enteric Bacteria of Food Animals as a Resistance Mitigation Strategy.

Antimicrobial drug use in food animals is associated with an elevation in relative abundance of bacteria resistant to the drug among the animal enteric bacteria. Some of these bacteria are potential foodborne pathogens. Evidence suggests that at least in the enteric nontype-specific Escherichia coli, after treatment the resistance abundance reverts to the background pre-treatment levels, without further interventions. We hypothesize that it is possible to define the distribution of the time period after treatment within which resistance to the administered drug, and possibly other drugs in case of coselection, in fecal bacteria of the treated animals returns to the background pre-treatment levels. Furthermore, it is possible that a novel resistance mitigation strategy for microbiological food safety could be developed based on this resistance reversion phenomenon. The strategy would be conceptually similar to existing antimicrobial drug withdrawal periods, which is a well-established and accepted mitigation strategy for avoiding violative drug residues in the edible products from the treated animals. For developing resistance-relevant withdrawals, a mathematical framework can be used to join the necessary pharmacological, microbiological, and animal production components to project the distributions of the post-treatment resistance reversion periods in the production animal populations for major antimicrobial drug classes in use. The framework can also help guide design of empirical studies into the resistance-relevant withdrawal periods and development of mitigation approaches to reduce the treatment-associated elevation of resistance in animal enteric bacteria. We outline this framework, schematically and through exemplar equations, and how its components could be formulated.

Evaluation of certain veterinary drug residues in food. Eighty-first report of the Joint FAO/WHO Expert Committee on Food Additives.

This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of residues of certain veterinary drugs in food and to recommend maximum levels for such residues in food. The first part of the report considers general principles regarding the evaluation of residues of veterinary drugs within the terms of reference of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), including MRLs for generic fish species, acute reference doses (ARfDs) for veterinary drugs, an approach for dietary exposure assessment of compounds used for multiple purposes (i.e veterinary drugs and pesticides), dietary exposure assessment for less-than-lifetime exposure, and the assessment of short-term (90-day and 12-month) studies in dogs. Summaries follow of the Committee's evaluations of toxicological and residue data on a variety of veterinary drugs: two insecticides (diflubenzuron and teflubenzuron), an antiparasitic agent (ivermectin), an ectoparasiticide (sisapronil) and a ß2-adrenoceptor agonist (zilpaterol hydrochloride). In addition, the Committee considered issues raised in concern forms from the Codex Committee on Residues of Veterinary Drugs in Foods on lasalocid sodium, an antiparasitic agent. Annexed to the report is a summary of the Committee's recommendations on these drugs, including acceptable daily intakes (ADIs), ARfDs and proposed MRLs.

Fish Oil Contaminated with Persistent Organic Pollutants Reduces Antioxidant Capacity and Induces Oxidative Stress without Affecting Its Capacity to Lower Lipid Concentrations and Systemic Inflammation in Rats.

BACKGROUND: Numerous studies have investigated the benefits of fish, fish oil, and ω-3 (n-3) polyunsaturated fatty acids against cardiovascular diseases. However, concern surrounding contamination with persistent organic pollutants (POPs) prompts caution in the recommendation to consume fish and fish oil. OBJECTIVE: The present study compared the effects of fish oil contaminated with polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCs) on serum lipid profiles, inflammation, and oxidative stress. METHODS: Twenty eight-day-old male Sprague-Dawley rats (n = 30) consumed diets of unmodified fish oil (FO) consisting of 15% fat by weight, persistent organic pollutant-contaminated fish oil (POP FO) (PCBs at 2.40 µg/g; OCs at 3.80 µg/g FO), or corn oil (control; CO) for 9 wk. Lipid profiles and C-reactive protein concentrations were assessed. Hepatic gene expression related to lipid metabolism was determined by real time quantitative polymerase chain reaction analysis. RESULTS: After 9 wk of feeding, accumulation of PCBs and OCs in the fat tissue of the POP FO group compared with the other 2 groups was confirmed (P < 0.01). Both fish oil groups showed greater HDL cholesterol (FO 53 ± 5.3 and POP FO 55 ± 7.7 vs. CO 34 ± 2.3 mg/dL), but lower triglycerides (24 ± 2.8 and 22 ± 3.0 vs. 43 ± 5.6 mg/dL), LDL cholesterol (38 ± 14 and 34 ± 9.2 vs. 67 ± 4.4 mg/dL), and C-reactive protein (113 ± 20 and 120 ± 26 vs. 189 ± 22 µg/dL) compared with the CO group (P < 0.05). Gene expression of fatty acid synthase in both fish oil groups was also less than in the CO group (P < 0.05). However, the POP FO group showed greater lipid peroxidation (5.1 ± 0.7 vs. 2.9 ± 0.9 and 2.6 ± 0.6 µM) and less antioxidant capacity (0.08 ± 0.06 vs. 0.5 ± 0.1 and 0.4 ± 0.1 mM) than the CO and FO groups (P < 0.05). CONCLUSIONS: These findings indicate that, despite exhibiting benefits on serum lipid concentrations and inflammation, contamination with PCBs and OCs showed significant negative effects on oxidative stress and antioxidant capacity in rats. Future studies should investigate the effects of different contaminant doses and the possibility of a dose-dependent response, a lengthened feeding time, and interactions between contaminant mixtures and oils of varying composition to advise on dietary consumption of fish and fish oil.

Diagnostic opportunities for evaluation of the exposure of dairy cows to the mycotoxins deoxynivalenol (DON) and zearalenone (ZEN): reliability of blood plasma, bile and follicular fluid as indicators.

To investigate the usefulness of follicular fluid (FF) in relation to blood plasma and bile as indicators of exposure of dairy cows to ZEN, DON and their metabolites, a dose-response study was performed with 30 dairy cows. The cows, 10 in each group (named CON; FUS-50, FUS-100), received a diet with three different concentrations of Fusarium toxin-contaminated maize. Thereby, the following dietary concentration were reached: CON (0.02 mg ZEN and 0.07 mg DON, per kg dry matter, DM), FUS-50 (0.33 mg ZEN and 2.62 mg DON, per kg DM) and FUS-100 (0.66 mg ZEN and 5.24 mg DON, per kg DM). ZEN, DON and de-epoxy-DON (de-DON) were detected in FF. Based on the linear regression between toxin concentration in plasma and FF, it seems that about 50% (m = 0.5) of ZEN present in plasma is present in FF while an increase of 1 ng/ml DON or de-DON in plasma is paralleled by an increase of 1.5 ng/ml DON or 1.1 ng/ml de-DON in FF. ZEN, DON and their metabolites, except zearalenone (ZAN), were also detected in bile. Contrary to DON and de-DON, ZEN and its metabolites were accumulated in bile so that the concentration of ZEN and metabolites was much higher than for DON and de-DON. The main compound was ß-zearalenol (ß-ZEL). The biliary ZEN, α-zearalenol (α-ZEL) and ß-ZEL concentration correlated linearly with each other with an uncertainty of <15% (r(2) ≥ 0.86), whereas the ratio between ZEN: α-ZEL: ß-ZEL was about 1.5:1:11. With the help of established linear relationship between toxin intake and toxin concentration, bile could be used as diagnostic indicator to assess the exposure of cows.

In vitro selection of RNA aptamers that selectively bind danofloxacin.

Danofloxacin is a synthetic fluoroquinolone with broad spectrum antibacterial activity that is used for the treatment of respiratory diseases in animal husbandry. However, danofloxacin has many adverse reactions and is toxic to humans. Especially, it detrimentally affects muscle, central nerve system, peripheral nerve system, liver, and skin in those who ingest foods in which danofloxacin has accumulated. Prescreening and determination of the level of danofloxacin in foods or food products is necessary for human health. Aptamers are composing of oligonucleotides that specifically interact with target molecules. They are emerging as detection/diagnostic ligands. Here, we used the SELEX in vitro selection technology to identify specific and high-affinity RNA aptamers with 2'-fluoro-2'-deoxyribonucleotide modified pyrimidine nucleotides against danofloxacin. Selected RNA aptamers bound specifically to danofloxacin, but not to tetracycline. Truncation of RNA aptamer up to 36 mer did not comprise specificity and affinity. The truncated RNA aptamer specifically bound to target chemical, allowing the discrimination of danofloxacin from other fluoroquinolones. The isolated specific aptamer could be a potential agent used for the rapid and cost-effective detection and sensing of danofloxacin, replacing instrumental methods including the more expensive and time-consuming methods of high performance liquid chromatography and liquid chromatography/mass spectrometry.

Enantioselective acute toxicity effects and bioaccumulation of furalaxyl in the earthworm (Eisenia foetida).

The enantioselectivities of individual enantiomers of furalaxyl in acute toxicity and bioaccumulation in the earthworm (Eisenia foetida) were studied. The acute toxicity was tested by filter paper contact test. After 48 h of exposure, the calculated LC50 values of the R-form, rac-form, and S-form were 2.27, 2.08, and 1.22 µg cm(-2), respectively. After 72 h of exposure, the calculated LC50 values were 1.90, 1.54, and 1.00 µg cm(-2), respectively. Therefore, the acute toxicity of furalaxyl enantiomers was enantioselective. During the bioaccumulation experiment, the enantiomer fraction of furalaxyl in earthworm tissue was observed to deviate from 0.50 and maintained a range of 0.55-0.60; in other words, the bioaccumulation of furalaxyl was enantioselective in earthworm tissue with a preferential accumulation of S-furalaxyl. The uptake kinetic of furalaxyl enantiomers fitted the first-order kinetics well and the calculated kinetic parameters were consistent with the low accumulation efficiency.

Adsorbents Reduce Aflatoxin M1 Residue in Milk of Healthy Dairy Cow Exposed to Moderate Level Aflatoxin B1 in Diet and Its Exposure Risk for Humans.

This study investigated the effect of moderate risk level (8 µg/kg) AFB1 in diet supplemented with or without adsorbents on lactation performance, serum parameters, milk AFM1 content of healthy lactating cows and the AFM1 residue exposure risk in different human age groups. Forty late healthy lactating Holstein cows (270 ± 22 d in milk; daily milk yield 21 ± 3.1 kg/d) were randomly assigned to four treatments: control diet without AFB1 and adsorbents (CON), CON with 8 µg/kg AFB1 (dry matter basis, AF), AF + 15 g/d adsorbent 1 (AD1), AF + 15 g/d adsorbent 2 (AD2). The experiment lasted for 19 days, including an AFB1-challenge phase (day 1 to 14) and an AFB1-withdraw phase (day 15 to 19). Results showed that both AFB1 and adsorbents treatments had no significant effects on the DMI, milk yield, 3.5% FCM yield, milk components and serum parameters. Compared with the AF, AD1 and AD2 had significantly lower milk AFM1 concentrations (93 ng/L vs. 46 ng/L vs. 51 ng/L) and transfer rates of dietary AFB1 into milk AFM1 (1.16% vs. 0.57% vs. 0.63%) (p < 0.05). Children aged 2-4 years old had the highest exposure risk to AFM1 in milk in AF, with an EDI of 1.02 ng/kg bw/day and a HI of 5.11 (HI > 1 indicates a potential risk for liver cancer). Both AD1 and AD2 had obviously reductions in EDI and HI for all population groups, whereas, the EDI (≥0.25 ng/kg bw/day) and HI (≥1.23) of children aged 2-11 years old were still higher than the suggested tolerable daily intake (TDI) of 0.20 ng/kg bw/day and 1.00 (HI). In conclusion, moderate risk level AFB1 in the diet of healthy lactating cows could cause a public health hazard and adding adsorbents in the dairy diet is an effective measure to remit AFM1 residue in milk and its exposure risk for humans.

Predicted critical environmental concentrations for 500 pharmaceuticals.

A growing number of pharmaceuticals are found in surface waters worldwide, raising concerns about their effects on aquatic organisms and it is a major challenge to develop a rational strategy for prioritizing drugs on which to focus the most extensive environmental research efforts. However, in contrast to most other chemicals, very good understanding of the human potency of pharmaceuticals has been obtained through efficacy and safety testing. Assuming that a drug acts primarily through the same target(s) also in a non-target species, it would be possible to predict the likelihood for pharmacological interactions in wildlife. Among aquatic organisms, fish most often share drug targets with humans. In this study, we have calculated the predicted critical environmental concentration (CECs), i.e. the surface water concentration expected to cause a pharmacological effect in fish, for 500 pharmaceuticals, assuming equivalent pharmacological activity. The CECs are based on literature data on human potencies together with a predicted bioconcentration factor in fish for each drug based on lipophilicity. We propose that CECs could be used as preliminary indicators of specific drugs' potential to cause adverse pharmacological effects at specific water concentrations, used when selecting pharmaceuticals to include in screening campaigns and for assessing relevant detection limits.

Evaluation of zebrafish DNA integrity after exposure to pharmacological agents present in aquatic environments.

Over the past few years, the increasing and uncontrolled use of pharmaceutical substances in agriculture, fish farming, human health and in veterinary medicine, together with an improper use of out-of-date medicines, has led to a consequent increase in the environmental problems linked to their disposal. In some Italian waste water treatment plants were found furosemide, a diuretic; ranitidine, an antiulcer drug; bezafibrate, a lipid regulator and ibuprofen, a painkiller. The present paper shows, by means of the synergic application of three tests (the Comet Test, the Diffusion Assay and the RAPD-PCR technique), how the DNA of zebrafish can be damaged after exposure to the above mentioned drugs. The data from the Comet Test, the Diffusion Assay and the RAPD-PCR technique were generally in agreement; these results show that all four drugs are genotoxic.

Characterization of additional sewage treatment technologies: ecotoxicological effects and levels of selected pharmaceuticals, hormones and endocrine disruptors.

In the present study, two conventional (with and without sand filter) and four additional (moving bed biofilm reactor, ozone, moving bed biofilm reactor combined with ozone and a membrane bio reactor) treatment technologies were operated in small-scale at Hammarby Sjöstad sewage treatment plant, Stockholm, Sweden. The effluents were tested with five short-term (≤ 7 days exposure) ecotoxicological tests, and analyzed for a number of target analytes, comprising pharmaceuticals, natural hormones and industrial chemicals. Overall, the tested effluents generated few adverse effects at lower concentrations (< 50% sewage effluent), and no major differences were observed between any of the treatments. The effluent treated with the moving bed biofilm reactor resulted in the lowest effects in the ecotoxicological tests. The most efficient treatment technology with regard to the pharmaceutical residues was the ozone treatment, which however caused negative effects in some of the ecotoxicological tests.

Lasalocid awareness and sampling in Scotland.

Lasalocid is an ionophore antibiotic extensively used as a coccidiostat in poultry production. Lasalocid should not be fed to egg-laying hens as it accumulates in the eggs, and residues have often been found in eggs. Other ionophores are toxic to humans, but the exact level of lasalocid toxicity to humans has not been established. Approximately 250 egg samples were analysed for lasalocid each year from the 10 billion eggs consumed annually in the UK. A census of the 32 Scottish Local Authority Environmental Health Departments assessed awareness of lasalocid residues in eggs, and the results indicated that awareness of lasalocid was very low and no local authorities tested for lasalocid. The example of lasalocid revealed weaknesses in the current sampling regime surrounding foods of animal origin. Conclusions are drawn that central government should raise awareness within local authorities and provide financial support on local authority sampling to achieve proper representation.

Health risk assessment of toxicologically relevant residues in emerging countries: A pilot study on Malachite Green residues in farmed freshwater fish of Armenia.

Malachite Green (MG) has a worldwide application in aquaculture as a therapeutic agent; however, its use in food producing animals is illegal, due to potential carcinogenicity and persistence of residues. This pilot study, the first conducted in Armenia, aimed to determine the concentration of MG residues in flesh of fish grown in artificial ponds of Armenia and conduct dietary exposure assessment to characterize possible health risks to consumers. Detection of MG residues, including the major metabolite leucomalachite, was carried out in 29 fish composite samples by ELISA. The results were confirmed by LC-MS/MS. To determine fish consumption values, a food frequency questionnaire was used. Possible health risks were evaluated by calculating the Margin of Exposure (MOE) based on BMDL of 13 (neoplastic effects) and 6 (non-neoplastic effects) mg/kg bw. In 34.5% of the investigated fish samples MG residues exceeded the minimum required performance limit. For BMDL10 and BMDL0.5, the MOEs ranged 3.36E+06-3.37E+07 and 1.55E+06-1.55E+07, respectively. The MOE for neoplastic effects was more than 10,000 and for non-neoplastic effects was more than 100. The results do not indicate public health concerns. However, the results highlight issues concerning the illegal use of MG in Armenian aquaculture, which deserves further attention.

Implications of Endectocide Residues on the Survival of Aphodiine Dung Beetles: A Meta-Analysis.

It is often difficult to compare studies examining the effects of endectocides on dung fauna because of different experimental approaches, for example, active ingredients (eprinomectin, doramectin, ivermectin, moxidectin) and formulations (injectable, pour-on, spiked). To gain a better understanding, we performed a quantitative meta-analysis using 22 studies to assess the overall effect of endectocide residues on the occurrence (presence or absence) and abundance of aphodiine dung beetles. Our results document a positive effect on the occurrence of adult beetles, indicating that adults tend to be attracted to dung with residues. Conversely, larvae are less likely to occur in the presence of residues. Thus, either adults that colonize dung with residues do not lay eggs or, more likely, the larvae that hatch from these eggs die early in development. Abundance of adult and larval stages was shown to be significantly reduced in dung containing residues. When individual endectocides were compared, only ivermectin demonstrated a significantly negative effect on the abundance of both adults and larvae, possibly owing to a small sample size for other agents. In laboratory studies, only dung "spiked" with endectocides reduced the abundance of larvae, whereas during field research, only pour-on applications were shown to reduce the abundance of larvae. The present study further documents the nontarget effects of endectocide residues on dung-dwelling organisms, provides robust evidence on the consequences of different application methods, and emphasizes the need for standardized methodological techniques in future studies. Environ Toxicol Chem 2020;39:863-872. © 2020 SETAC.

The effects of residual tetracycline on soil enzymatic activities and plant growth.

A pot trial was carried out to investigate the adverse effects of tetracycline (TC) on soil microbial communities, microbial activities, and the growth of ryegrass (Lolium perenne L). The results showed that the presence of TC significantly disturbed the structure of microbial communities and inhibited soil microbial activities in terms of urease, acid phosphatase and dehydrogenase (p < 0.05). Plant biomass was adversely influenced by TC, especially the roots with a reduction of 40% when compared with the control. Furthermore, TC decreased the assimilation of phosphorus by the plant although the concentration of phosphorus was increased by 20% due to decreased plant biomass. TC seemed to increase the concentration of dissolved organic carbon (by 20%) in soil. The findings implied that the agricultural use of animal manure or fishpond sediment containing considerable amounts of antibiotics may give rise to ecological risks.