Exposure pathways and ecological risk assessment of common veterinary antibiotics in the environment through poultry litter in Bangladesh

Tetracycline and fluoroquinolone antibiotics contamination in agricultural soils fertilized long-term with chicken litter: Trends and ravages

We investigated the potential accumulation of tetracyclines (TCs) such as chlortetracycline (CTC), oxytetracycline (OTC) and doxycycline (DC), and fluoroquinolones (FQs) like enrofloxacin (ENR) and ciprofloxacin (CIP) in chicken litter and agricultural soils fertilized over short-term to long-term (<1-30 yrs) with chicken litter in a poultry hub for the first time from Tamil Nadu, India. CTC, OTC, DC, CIP, and ENR were detected in 46-92 % of the selected chicken litter samples, with mean levels ranging from 2.90 to 23.30 μg kg-1. Higher concentrations of TCs and FQs were observed in freshly collected chicken litter from poultry sheds than in those stockpiled in cultivated lands. CTC was the prevalent antibiotic in chicken litter. The overall occurrence, as well as the ecological risks of TCs and FQs, changed over a 30-yr period. The accumulation of veterinary antibiotics (VAs) (in μg kg-1) in short-term (>1 yr) to medium-term (1-3 yrs) chicken litter-fertilized soils reached a maximum of 11.60 for CTC, 6.50 for OTC, 0.80 for DC, 3.70 for CIP, and 3.60 for ENR, but decreased in long-term (10-30 yrs) fertilized soils. Ecological risk assessment revealed a Risk Quotient (RQ) of ≤0.10 for CTC, OTC, and DC in all soils, while an average risk (RQ >0.10-<1.0) was evident with CIP and ENR in short-term and medium-term fertilized soils. Antibiotic resistance genes (ARGs), including tetA, tetB, qnrA, qnrB and qnrS were detected in most of the chicken litter samples and litter-fertilized soils. Thus, it is critical to develop and adopt effective mitigation strategies before applying chicken litter in farmlands to decrease VAs and ARGs, reducing their associated risks to public health and ecosystems in India considering 'One Health' approach. Future investigations on the occurrence of other VAs and ARGs in soils fertilized with poultry litter at regional scale are required for effective risk mitigation of the widely used VAs.

Is the Use of Monensin Another Trojan Horse for the Spread of Antimicrobial Resistance?

Antimicrobial resistance (AMR) is a complex and somewhat unpredictable phenomenon. Historically, the utilization of avoparcin in intensive farming during the latter part of the previous century led to the development of resistance to vancomycin, a crucial antibiotic in human medicine with life-saving properties. Currently, in the European Union, there is a growing reliance on the ionophore antibiotic monensin (MON), which acts both as a coccidiostat in poultry farming and as a preventative measure against ketosis in lactating cows. Although many researchers claim that MON does not induce cross-resistance to antibiotics of clinical relevance in human medicine, some conflicting reports exist. The numerous applications of MON in livestock farming and the consequent dissemination of the compound and its metabolites in the environment require further investigation to definitively ascertain whether MON represents a potential vector for the propagation of AMR. It is imperative to emphasize that antibiotics cannot substitute sound animal husbandry practices or tailored dietary regimens in line with the different production cycles of livestock. Consequently, a rigorous evaluation is indispensable to assess whether the economic benefits associated with MON usage justify its employment, also considering its local and global environmental ramifications and the potential risk of instigating AMR with increased costs for its control.

Review of antibiotic use and resistance in food animal production in WHO South-East Asia Region

Antimicrobial resistance is an emerging global threat to public health. The resistant bacteria in food animals can be transferred to humans through the food chain. Limited information on antimicrobial usage and resistance in food animals is available in Southeast Asia due to inadequate monitoring or surveillance systems. A literature review was conducted on antimicrobial use and resistance in food animal production in Southeast Asia for the period 2011-2020, to assess the scope and extent of antibiotic use and resistance. The countries included in the study were Bangladesh, Bhutan, Democratic People's Republic of Korea, India, Indonesia, Maldives, Myanmar, Nepal, Sri Lanka, Thailand and Timor-Leste. The information was categorised by country, production type and findings regarding antibiotic use and resistance. A total of 108 publications were included in the review. Results showed widespread use of critically and highly important antibiotics in livestock, poultry and aquacultured fish and their products. To curb the growing threat of antibiotic resistance, Southeast Asian countries need to strengthen surveillance and regulatory controls of antimicrobial use in food animal production through "One Health" approach.

Residues of veterinary antibiotics in manures from pig and chicken farms in a context of antimicrobial use reduction by implementation of health and welfare plans

The use of antibiotics in food-producing animals can induce the presence of residual substances in manure, which are then released into the environment and may contribute to soil and groundwater contamination. During the on-farm implementation of strategies to improve animal health and welfare in chicken and pig farms, the consequences of antibiotic use were evaluated in terms of the occurrence and levels of antibiotic residues in manure. A set of 35 broiler farms from Cyprus, Greece, the Netherlands and 40 pig farms from France and Italy provided a total of 350 manure samples. The primary objective was to develop a specific LC/MS/MS method capable of quantifying antibiotic residues in both types of manure. The method was able to detect fifteen antibiotics belonging to nine classes, with validated limits of quantification of 10-20 μg/kg, and accuracies ranging from 81% to 138%. With the exception of amoxicillin, which was never detected in any manure, all antibiotics used were detected in manure from treated animals with typical concentrations ranging from 10 to 99198 μg/kg for both chickens and pigs. The occurrence of residual antibiotics was higher in chicken than in pig manure, especially for fluoroquinolones and doxycycline which were detected in 89% and 100% of the chicken manure, respectively, and in 28% of the pig manure. The impact of the health plans on the antibiotic load manure was assessed by measuring for each farm the ratio of the sum of all antibiotic concentrations measured after and before the implementation of the plan. The results showed that, in addition to the frequency of treatments, the class of antibiotic used is an important factor to consider as it strongly influences the stability/instability of the compounds, i.e. their ability to persist in the manure of food-producing animals.

Investigation of manganese-iron oxide nanocomposite immobilized on powdered activated carbon as an efficient activator of peroxymonosulfate for antibiotics degradation: Conjunction of adsorption, radical and nonradical processes

Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) have gained considerable attention for their efficient oxidation of persistent pollutants. A two-step chemical co-precipitation method was used to prepare a bimetallic nanocomposite (MnOx@Fe3O4) consisting of manganese oxides and ferroferric oxides, supported by powdered activated carbon (PAC). The synthesis of MnOx@Fe3O4-PAC (MFP) was aimed to enhance the degradation efficiency of oxytetracycline (OTC) via the simultaneous adsorption and oxidation processes on the solid-liquid interface. The OTC degradation process in the MFP/PMS system could be well described by pseudo-first-order kinetics. A wide pH range (3-6) was acceptable for MFP to degrade OTC via PMS activation with the highest removal efficiency reaching up to 85.6% (OTC0 = 150 mg/L), while a 60.8% removal efficiency of total organic carbon (TOC) was also attained simultaneously. SO4•- and 1O2, which were bound to the surface, played a crucial role as reactive oxygen species in the degradation of OTC. The combination of PAC, Fe3O4, and MnOx of MFP could enhance the degradation efficiency of OTC and fetch up their defects of separate application. The deduced OTC degradation pathway relied on the findings from UPLC-MS analysis and density functional theory (DFT) calculations. Noteworthy, MFP maintained efficient catalysis performance in the five cycles of stability experiment with neglectable loss of manganese and iron. These results provide valuable understanding of the conjunction of adsorption, radical, and nonradical processes driven by MFP for OTC degradation.

Screening and quantification of antibiotic residues in poultry products and feed in selected areas of Bangladesh

Background and Aim

Antibiotic residues in livestock farming have been identified as a potential cause of antimicrobial resistance in humans and animals. This study aimed to determine whether antibiotic residues were present in the chicken meat, eggs, feces, and feed collected from all four districts in the Mymensingh division of Bangladesh.

Materials and Methods

To detect antibiotic residues in the collected samples, qualitative thin-layer chromatography (TLC) and quantitative high-performance liquid chromatography (HPLC) were used. A total of 230 samples were analyzed for antibiotic residues of commonly used 11 antibiotics. Out of these, 40 meat and 40 feces samples were collected from broilers and layers, 30 egg samples from ducks and layers, and 120 feed samples from broilers and layers from the study area. Thin-layer chromatography was used to screen the presence of antibiotic residues; TLC-positive samples were then subjected to further HPLC analysis to determine the residue concentrations.

Results

Thin-layer chromatography analysis revealed that 23.5% of the tested samples contained residues from six different antibiotic classes (tetracyclines, quinolones, beta-lactams, sulfonamides, aminoglycosides, and macrolides). Thin-layer chromatography analysis showed that 35% and 25% of the meat samples were positive for residues from the broiler and layer, respectively. About 15% and 30% of layer and duck egg samples had positive residues, respectively. Out of 120 feed samples analyzed, about 15.8% had various antibiotic residues. In addition, feces samples from broilers and layers had 50% and 35% antibiotic residues, respectively. A total of 2.5% meat and 3.3% egg samples had antibiotic residues above the maximum residue limit (MRL). Based on the findings of this study, the highest percentage of oxytetracycline, followed by doxycycline and ciprofloxacin, were detected in feed samples, and oxytetracycline was detected in meat and egg samples.

Conclusion

This study clearly showed the misuse of antibiotics in the poultry sector in Bangladesh. Although antibiotic residues below the MRL level are suitable for human consumption, they may result in antimicrobial drug resistance to pathogens.

Modelling approaches for linking the residual concentrations of antibiotics in soil with antibiotic properties and land-use types in the largest urban agglomerations in China: A review

Persistently high concentrations of antibiotics have been reported in soils worldwide due to the intensive use of veterinary antibiotics, and continuous adsorption and transport of various antibiotics in soils occur, posing a significant threat to the environment and human health. This study systematically reviews the spatial distribution and ecological risk of four commonly detected antibiotic residues in soil in China, including sulphonamides (SAs), fluoroquinolones (FQs), tetracyclines (TCs) and macrolides (MLs), using various models, such as redundancy analysis (RDA), principal coordinate analysis (PCoA) and structural equation modelling (SEM). Antibiotic residual concentration data were obtained from relevant repositories and the literature. The results suggest a high level of antibiotic pollution and ecological risk in the largest urban agglomerations (LUAs), including Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD) and Guangdong-Hong Kong-Macao Greater Bay Area (GBA), with a 100% detection rate. SAs, FQs, TCs and MLs were the dominant antibiotic residues in soils, mainly attributed to manure fertilization and wastewater reuse in agriculture. These antibiotic concentrations ranged from 10^-3 to 10³ μg kg^-1, and their ecological risk varied significantly across different regions of China, with SAs posing the most serious ecological risk to the soil environment (p < 0.05). These models established a significant association (p < 0.05) between the physicochemical properties of antibiotics and land-use type (LUT) with antibiotic residues in soil. The structure of the antibiotic exerted the greatest influence on antibiotic residues, followed by the LUT, while regional differences had the weakest effect.

Effects of litter from antimicrobial-fed broiler chickens on soil bacterial community structure and diversity

This study examined changes in soil bacterial community composition and diversity in response to fertilization with litter from chickens fed diet with no antibiotics, bambermycin, penicillin, bacitracin, salinomycin, and mix of salinomycin and bacitracin. Litter was applied to 24 agricultural-plots. Non-fertilized plots were used as a negative control. Soil samples collected from the studied plots were used to quantify Escherichia coli by plate counts, and Clostridium perfringens by qPCR. The 16S-rRNA gene sequencing was performed for microbiota analysis. Following litter application in December, the population size of E.coli was 5.4 log CFU/g, however, regardless of treatments the result revealed 5.2 and 1.4 log CFU/g of E.coli in soil sampled in January and March, respectively. Fertilization with antibiotic treated litter increased (P < 0.05) the relative abundance of Proteobacteria, Actinobacteria and Firmicutes in soil, but decreased Acidobacteria and Verrucomicrobia groups. The alpha-diversity parameters were higher (P < 0.05) in non-fertilized soil compared to the fertilized ones, suggesting that litter application was a major factor in shaping the soil bacterial communities. These results may help develop efficient litter management strategies like composting, autoclaving, or anaerobic digestion of poultry litter before application to land for preservation of soil health and crop productivity.

Uptake of Pharmaceutical Pollutants and Their Metabolites from Soil Fertilized with Manure to Parsley Tissues

Manure is a major source of soil and plant contamination with veterinary drugs residues. The aim of this study was to evaluate the uptake of 14 veterinary pharmaceuticals by parsley from soil fertilized with manure. Pharmaceutical content was determined in roots and leaves. Liquid chromatography coupled with tandem mass spectrometry was used for targeted analysis. Screening analysis was performed to identify transformation products in the parsley tissues. A solid-liquid extraction procedure was developed combined with solid-phase extraction, providing recoveries of 61.9–97.1% for leaves and 51.7–95.6% for roots. Four analytes were detected in parsley: enrofloxacin, tylosin, sulfamethoxazole, and doxycycline. Enrofloxacin was detected at the highest concentrations (13.4–26.3 ng g⁻¹). Doxycycline accumulated mainly in the roots, tylosin in the leaves, and sulfamethoxazole was found in both tissues. 14 transformation products were identified and their distribution were determined. This study provides important data on the uptake and transformation of pharmaceuticals in plant tissues.

Assessment of phytotoxicity and impact on the enzymatic activity of soil microorganisms caused by veterinary antibiotics used in Brazilian farms

This work aimed to evaluate the impact of veterinary antibiotics on biomass phytoproductivity and soil enzyme activity. The soil was sampled in the city of Camboriú (state of SC, Brazil). The soil enzyme activity was assessed through hydrolysis of fluorescein diacetate (FDA), while phytotoxicity was tested using Lactuca sativa (lettuce). Results showed that the most appropriate exposure time to assess the impact of antibiotics on soil microbiology was 24 h, while the incubation time of 3 h was the most appropriate for FDA hydrolysis. Ampicillin and Amoxicillin at the tested concentrations did not interfere with the enzyme activity of the soil microbiota, while Oxytetracycline and Neomycin showed a significant reduction in soil enzyme activity. For the dry and wet biomass of lettuce, 2% Colistin and 1% Ampicillin were the treatments that reduced lettuce biomass. Hence, the use of excessive antibiotics in animal production may lead to environmental impacts and, in the future, to public health problems.

Evaluation of Antibiotic Dissemination into the Environment and Untreated Animals, by Analysis of Oxytetracycline in Poultry Droppings and Litter

Simple Summary

Oxytetracycline (OTC) is an antibiotic used mainly in feed and drinking water. OTC is poorly absorbed in the gastrointestinal tract of poultry; making droppings a potential route of dissemination of this antibiotic. The aim of this study was to evaluate the dissemination of oxytetracycline excreted from treated birds to the environment and other untreated animals (sentinels), through the analysis of their droppings and litter by HPLC-MS/MS following the end of treatment. In treated bird droppings, the average concentration of OTC+4-epi-OTC ranged from 347.63 to 2244.66 µg kg⁻¹. OTC+4-epi-OTC in litter reached concentrations of 22,741.68 µg kg⁻¹. Traces of OTC+4-epi-OTC were detected in the droppings and litter from sentinels. Therefore, OTC+4-epi-OTC can persist in the litter of treated animals at high concentrations and can be transferred to untreated birds that share the same environment. This exposure has the potential to increase the likelihood of selection of resistant bacteria in the environment.

Abstract

Oxytetracycline (OTC) is widely used in broiler chickens. During and after treatment a fraction of OTC is excreted in its original form and as its epimer, 4-epi-OTC in droppings. To address the transfer of OTC into the environment, we evaluated the dissemination of OTC and 4-epi-OTC from treated birds to the environment and sentinels, through the simultaneous analysis of broiler droppings and litter. Male broiler chickens were bred in controlled conditions. One group was treated by orogastric tube with 80 mg kg⁻¹ of OTC and two groups received no treatment (sentinels). OTC+4-epi-OTC were analyzed and detected by a HPLC-MS/MS post the end of treatment. The highest concentrations of OTC+4-epi-OTC were detected in the droppings of treated birds 14-days following the end of treatment (2244.66 µg kg⁻¹), and one day following the end of treatment in the litter (22,741.68 µg kg⁻¹). Traces of OTC+4-epi-OTC were detected in the sentinels’ droppings and litter (<12.2 µg kg⁻¹). OTC+4-epi-OTC can be transferred from treated birds to the environment and to other untreated birds. The presence and persistence of OTC+4-epi-OTC in litter could contribute to the selection of resistant bacteria in the environment, increasing the potential hazard to public and animal health.