Use of a filtering process to remove solid waste and antibiotic resistance genes from effluent of a flow-through fish farm

Biosecurity and water, sanitation, and hygiene (WASH) interventions in animal agricultural settings for reducing infection burden, antibiotic use, and antibiotic resistance: a One Health systematic review

Prevention and control of infections across the One Health spectrum is essential for improving antibiotic use and addressing the emergence and spread of antibiotic resistance. Evidence for how best to manage these risks in agricultural communities-45% of households globally-has not been systematically assembled. This systematic review identifies and summarises evidence from on-farm biosecurity and water, sanitation, and hygiene (WASH) interventions with the potential to directly or indirectly reduce infections and antibiotic resistance in animal agricultural settings. We searched 17 scientific databases (including Web of Science, PubMed, and regional databases) and grey literature from database inception to Dec 31, 2019 for articles that assessed biosecurity or WASH interventions measuring our outcomes of interest; namely, infection burden, microbial loads, antibiotic use, and antibiotic resistance in animals, humans, or the environment. Risk of bias was assessed with the Systematic Review Centre for Laboratory Animal Experimentation tool, Risk of Bias in Non-Randomized Studies of Interventions, and the Appraisal tool for Cross-Sectional Studies, although no studies were excluded as a result. Due to the heterogeneity of interventions found, we conducted a narrative synthesis. The protocol was pre-registered with PROSPERO (CRD42020162345). Of the 20 672 publications screened, 104 were included in this systematic review. 64 studies were conducted in high-income countries, 24 studies in upper-middle-income countries, 13 studies in lower-middle-income countries, two in low-income countries, and one included both upper-middle-income countries and lower-middle-income countries. 48 interventions focused on livestock (mainly pigs), 43 poultry (mainly chickens), one on livestock and poultry, and 12 on aquaculture farms. 68 of 104 interventions took place on intensive farms, 22 in experimental settings, and ten in smallholder or subsistence farms. Positive outcomes were reported for ten of 23 water studies, 17 of 35 hygiene studies, 15 of 24 sanitation studies, all three air-quality studies, and 11 of 17 other biosecurity-related interventions. In total, 18 of 26 studies reported reduced infection or diseases, 37 of 71 studies reported reduced microbial loads, four of five studies reported reduced antibiotic use, and seven of 20 studies reported reduced antibiotic resistance. Overall, risk of bias was high in 28 of 57 studies with positive interventions and 17 of 30 studies with negative or neutral interventions. Farm-management interventions successfully reduced antibiotic use by up to 57%. Manure-oriented interventions reduced antibiotic resistance genes or antibiotic-resistant bacteria in animal waste by up to 99%. This systematic review highlights the challenges of preventing and controlling infections and antimicrobial resistance, even in well resourced agricultural settings. Most of the evidence emerges from studies that focus on the farm itself, rather than targeting agricultural communities or the broader social, economic, and policy environment that could affect their outcomes. WASH and biosecurity interventions could complement each other when addressing antimicrobial resistance in the human, animal, and environmental interface.

Temporal variations, distribution, and dissemination of antibiotic resistance genes and changes of bacterial communities in a biofloc-based zero-water-exchange mariculture system

Antibiotic resistance genes (ARGs) have obtained an increasing number of global concerns for the severe risks they pose to food safety and public health. Studies have investigated the concentrations and distribution of ARGs in the environment. However, the distribution and dissemination of ARGs, the bacterial communities, and the key influencing factors during the entire rearing period in the biofloc-based zero-water-exchange mariculture system (BBZWEMS) remain unclear. The current study investigated the concentrations, temporal variations, distribution, and dissemination of ARGs, the changes in the bacterial communities, as well as the key influencing factors during the rearing period in the BBZWEMS. Sul1 and sul2 were dominant ARGs. Total concentrations of ARGs followed a trend of decrease in pond water, while they followed a trend of increase in source water, biofloc, and shrimp gut. Total concentrations of targeted ARGs in the water source were higher than those in the pond water and biofloc samples for each corresponding rearing stage by 2.25-122.97-fold (p < 0.05). The bacterial communities in biofloc and pond water did not change much, while they changed considerably in the shrimp gut samples during the rearing period. Pearson correlation, redundancy analysis, and multivariable linear regression analysis showed that suspended substances and Planctomycetes were positively correlated with the concentrations of ARGs (p < 0.05). The current study indicates that the water source may be a critical source of ARGs, and that suspended substances is a key factor influencing the distribution and dissemination of ARGs in the BBZWEMS. Early intervention measures on ARGs in water sources should be implemented to aid in the prevention and control of resistance genes in aquaculture industry, and reduce the potential risks of ARGs to public health and food safety.

Spatial and temporal effects of fish feed on antibiotic resistance in coastal aquaculture farms

For the first time, both spatial and temporal effects of fish feed on changes in abundance of antibiotic resistance genes (ARGs) were investigated in South Korea via quantifying ARGs and analyzing physicochemical parameters in the influent (IN) and effluent before (BF) and 30 min after (AF) the fish feeding time of sixteen flow-through fish farms. The absolute abundance of ARGs in AF samples was 5 times higher than in BF and 12 times higher than in IN samples. Values of physicochemical parameters such as ammonia, total nitrogen, suspended solids and turbidity in the effluent significantly increased by 21.6, 4.2, 2.6 and 1.65 times, respectively, after fish feeding. Spatially, the fish farms on Jeju Island exhibited higher relative abundance (3.02 × 10^-4 - 6.1 × 10^-2) of ARGs compared to the farms in nearby Jeollanam-do (3.4 × 10^-5 - 8.3 × 10^-3). Seasonally, samples in summer and autumn showed a higher abundance of ARGs than in winter and spring. To assess risk to the food chain as well as public health, further studies are warranted to explore the pathogenic potential of these ARGs.

Antibiotic Susceptibility of Bacterial Pathogens That Infect Olive Flounder (Paralichthys olivaceus) Cultivated in Korea

Paralichthys olivaceus (olive flounder) is widely cultivated in Korea. However, data on the antibiotic susceptibility of bacterial pathogens that infect olive flounders in Korea are limited. The susceptibility of 84 strains of 3 pathogenic bacteria (Streptococcus spp., Vibrio spp., and Edwardsiella piscicida) to 18 antibiotics was tested using the minimum inhibitory concentration (MIC) panels, and the distribution of the MIC values for each species was confirmed. Among the panel antibiotics, nine commonly used antibiotics were selected, and the multiple antibiotic resistance (MAR) index and antibiotic resistance pattern were indicated using the disk diffusion method. It was confirmed that most of the isolates had a MAR index greater than 0.2, indicating a high-risk source. The distribution patterns of the MIC values and resistance pattern between gram-positive and gram-negative bacteria showed slightly different results. Ampicillin, erythromycin, and clindamycin were more effective against gram-positive bacteria than gram-negative bacteria. However, the MIC values of flumequine for gram-positive bacteria were higher than those of gram-negative bacteria. Through the distribution patterns of the MIC values and resistance patterns presented in this study, the need for monitoring the multidrug-resistant bacteria in aquaculture is emphasised.

Bacterial-algal coupling system for high strength mariculture wastewater treatment: Effect of temperature on nutrient recovery and microalgae cultivation

In the present study, bacterial-algal coupling system, an integration process of acidogenic fermentation and microalgae cultivation was used for high strength mariculture wastewater (HSMW) treatment, resource recovery and low-cost biomass production. The effect of temperature on Chlorella vulgaris (C. vulgaris) cultivation was investigated with culture medium of acidogenic liquid. The results showed that acidogenic liquid could be used as culture medium for C. vulgaris and higher biomass was obtained compared to control. The acidogenic liquid obtained at initial pH of 8 was the most suitable culture medium for C. vulgaris growth due to befitting C/N and considerable volatile fatty acids. Moreover, the optimum temperature for C. vulgaris cultivation was 25 °C and the removal efficiency of chemical oxygen demand (COD) and NH₄⁺-N from acidogenic liquid could reach 94.4% and 68.8%, respectively. The outcome could create an innovative value chain with environmental sustainability and economic feasibility in aquaculture industry.

Antibiotics, Multidrug-Resistant Bacteria, and Antibiotic Resistance Genes: Indicators of Contamination in Mangroves?

Multidrug-resistant bacteria and antibiotic resistance genes can be monitored as indicators of contamination in several environments. Mangroves are among the most productive ecosystems, and although they can be resilient to the action of climate phenomena, their equilibrium can be affected by anthropogenic activities. Regarding the presence and persistence of multidrug-resistant bacteria in mangroves, it is common to think that this ecosystem can function as a reservoir, which can disperse the antibiotic resistance capacity to human pathogens, or serve as a filter to eliminate drug-resistant genes. The possible impact of anthropogenic activities carried out near mangroves is reviewed, including wastewater treatment, food production systems, leisure, and tourism. Adverse effects of antibiotic resistance genes or multidrug-resistant bacteria, considered as emerging contaminants, have not been reported yet in mangroves. On the contrary, mangrove ecosystems can be a natural way to eliminate antibiotics, antibiotic-resistant bacteria, and even antibiotic-resistant genes from the environment. Although mangroves’ role in decreasing antibiotics and antibiotic resistance genes from the environment is being proposed, the mechanisms by which these plants reduce these emerging contaminants have not been elucidated and need further studies. Additionally, further evaluation is needed on the effects of antibiotics and antibiotic-resistant bacteria in mangroves to generate an analysis of the human contribution to the degradation of this specific ecosystem as well as to define if these contaminants can be used as indicators of contamination in mangrove ecosystems.

Distribution of genetic elements associated with antibiotic resistance in treated and untreated animal husbandry waste and wastewater

Animal breeding for meat production based on swine, cattle, poultry, and aquaculture is an activity that generates several impacts on the environment, among them the spread of antibiotic resistance. There is a worldwide concern related to the massive use of antibiotics, which causes selective pressure on the microbial community, triggering bacteria that contain "antibiotic resistance genes." According to the survey here presented, antibiotic resistance-related genes such as tetracyclines (tet), erythromycin (erm), and sulfonamides (sul), as well as the genetic mobile element interferon (int), are the most reported genetic elements in qualitative and quantitative studies of swine, cattle, poultry, and aquaculture manure/wastewater. It has been observed that biological treatments based on waste composting and anaerobic digestion are effective in ARG removal, particularly for tet, bla, erm, and qnr (quinolone) genes. On the other hand, sul and intI genes were more persistent in such treatments. Tertiary treatments, such advanced oxidative processes, are suitable strategies to improve ARG reduction. In general temperature, hydraulic retention time, and penetration of sunlight are the main operational parameters for ARG reduction in treatments applied to animal waste, and therefore attention should be addressed to optimize their efficacy regarding ARG removal. Despite being reduced, the presence of ARG in treated effluents and in biosolids indicates that there is a potential risk of antibiotic resistance spread in nature, especially through the release of treated livestock waste into the environment.

Designing a marine outfall to reduce microbial risk on a recreational beach: Field experiment and modeling

A marine outfall can be a wastewater management system that discharges sewage and stormwater into the sea; hence, it is a source of microbial pollution on recreational beaches, including antibiotic resistant genes (ARGs), which lead to an increase in untreatable diseases. In this regard, a marine outfall must be efficiently located to mitigate these risks. This study aimed to 1) investigate the spatiotemporal variability of Escherichia coli (E. coli) and ARGs on a recreational beach and 2) design marine outfalls to reduce microbial risks. For this purpose, E. coli and ARGs with influential environmental variables were intensively monitored on Gwangalli beach, South Korea in this study. Environmental fluid dynamic code (EFDC) was used and calibrated using the monitoring data, and 12 outfall extension scenarios were explored (6 locations at 2 depths). The results revealed that repositioning the marine outfall can significantly reduce the concentrations of E. coli and ARGs on the beach by 46-99%. Offshore extended outfalls at the bottom of the sea reduced concentrations of E. coli and ARGs on the beach more effectively than onshore outfalls at the sea surface. These findings could be helpful in establishing microbial pollution management plans at recreational beaches in the future.

Fish farm effluents as a source of antibiotic resistance gene dissemination on Jeju Island, South Korea

The abuse or misuse of antibiotics is directly linked to the emergence of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) in the environment. Most fish farms located on Jeju Island operate a flow-through system that pumps in seawater for fish farming and discharges it back to the ocean. To investigate the amount of ARGs that these fish farm effluents discharge into the marine environment, we conducted a metagenomic-based resistome analysis. We observed higher levels of ARGs in fish farm effluents than in seawater at beach and residential areas. A greater proportion of ARGs was found on plasmid rather than on chromosomal DNA, especially for sulfonamide and phenicol classes. The distribution of ARGs did not differ between summer and winter, but the microbial community did. In addition, fish farm samples contained significantly more opportunistic pathogens (i.e., Vibrio, Photobacterium, Aliivibrio, and Tenacibaculum) and virulence factors than non-fish farm samples. Vibrio was the most frequently identified host of ARGs and virulence factors. The presence of Vibrio in the coastal area has been increasing owing to the recent rise in the temperature of seawater. This study suggests the need for actions to treat or monitor ARGs in the coastal areas where fish farms operating a flow-through system are located.

Antibiotics in coastal aquaculture waters: Occurrence and elimination efficiency in oxidative water treatment processes

The influents and effluents of coastal flow-through aquacultures in Korea were monitored for four selected antibiotics (amoxicillin-AMX, florfenicol-FLO, oxolinic acid-OXO, and oxytetracycline-OTC). A number of 177 samples were obtained from 16 aquaculture facilities for a monitoring period of two years. OTC was detected in 93 samples with a median concentration of 116 ng/L. OXO, FLO, and AMX were also detected in 36, 34, and 22 samples with median concentrations of 90, 44, and 63 ng/L, respectively. After antibiotics were applied to fish tanks, the aquaculture effluents were found to contain antibiotics up to several hundred μg/L, indicating that some control measures are required. Bench-scale experiments showed that chlorine and ozone fully eliminated AMX and OTC but not FLO at ≤2 mg/L of oxidant dosage. Reactive halogen species formed in the marine water matrix enhanced the antibiotic degradation. UV₂₅₄ most effectively eliminated FLO, achieving 60-70 % elimination at 1000 mJ/cm² of UV fluence. Sequential use of chlorine followed by UV₂₅₄ demonstrated significant elimination of all four selected antibiotics. The obtained kinetic information for the reactions of these oxidants and UV with the antibiotics and marine aquaculture water constituents could be useful for designing and optimizing the aquaculture water treatment processes.

Identification of Selected Antibiotic Resistance Genes in Two Different Wastewater Treatment Plant Systems in Poland: A Preliminary Study

Antibiotic resistance is a growing problem worldwide. The emergence and rapid spread of antibiotic resistance determinants have led to an increasing concern about the potential environmental and public health endangering. Wastewater treatment plants (WWTPs) play an important role in this phenomenon since antibacterial drugs introduced into wastewater can exert a selection pressure on antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Therefore, WWTPs are perceived as the main sources of antibiotics, ARB and ARG spread in various environmental components. Furthermore, technological processes used in WWTPs and its exploitation conditions may influence the effectiveness of antibiotic resistance determinants’ elimination. The main aim of the present study was to compare the occurrence of selected tetracycline and sulfonamide resistance genes in raw influent and final effluent samples from two WWTPs different in terms of size and applied biological wastewater treatment processes (conventional activated sludge (AS)-based and combining a conventional AS-based method with constructed wetlands (CWs)). All 13 selected ARGs were detected in raw influent and final effluent samples from both WWTPs. Significant ARG enrichment, especially for tet(B, K, L, O) and sulIII genes, was observed in conventional WWTP. The obtained data did not show a clear trend in seasonal fluctuations in the abundance of selected resistance genes in wastewaters.

Contamination of antibiotic resistance genes (ARGs) in a typical marine aquaculture farm: source tracking of ARGs in reared aquatic organisms

Although the prevalence and concentrations of antibiotic resistance genes (ARGs) in aquaculture is receiving increasing scientific interest, there is little understanding of the direct sources and dissemination pathways of ARGs in marine aquaculture-reared organisms. This study investigated the dynamics of ARGs and the bacterial community throughout the rearing period in a typical marine aquaculture farm in South China. The results demonstrated that sul1 and qnrD were predominant in the sediment, and qnrD and qnrA were predominant in the intestinal tracts of shrimps. Network analysis showed that the chemical oxygen demand, total organic carbon, dissolved organic carbon, suspended solids, and total phosphorus were positively correlated with the predominant ARGs. The results of the network and source tracking analyses indicate that environmental factors and the bacterial community may drive the dissemination of ARGs dissemination in the environment and in shrimp reared by marine aquaculture, and sediment is the most direct and important medium in this dissemination. These results aid in improving our understanding of the sources, level, and dissemination of ARGs in marine aquaculture.

Occurrence and reduction of antibiotic resistance genes in conventional and advanced drinking water treatment processes

Antibiotic resistance is extensively detected in drinking water sources, threatening its safety and human health, which deserves further attention to the removal of antibiotic resistance genes (ARGs) in the drinking water system. In this study, the occurrence and reduction of integrase gene intI1 and forty-one ARG subtypes, which confers resistance to six antibiotic classes (β-lactam, aminoglycoside, macrolide, tetracycline, sulfonamide, and quinolone), were investigated in a drinking water treatment plant (DWTP). Seventeen ARG subtypes with absolute concentrations ranging from 1.4 × 10⁰ to 7.3 × 10⁵ and 3.9 × 10⁴ genes/mL (intI1) were detected in the raw water; and sul1 and sul2 were the two dominant ARG subtypes. Overall, the whole DWTPs achieved 0.03-2.4 log reduction of ARGs compared with those presented in raw water. The reduction efficiencies of sul1, strA, and intI1 were the highest (1.0-2.4 log) in both conventional and advanced processes. However, the levels of sul1, sul2, and ermC still remained high (1.3 × 10⁰-1.9 × 10⁴ genes/mL) in finished water. The treatment units, including pre-flocculation/sedimentation/sand filtration, and ozonation units, were beneficial for the reduction of ARGs, which was mostly ascribed to the decline in biomass and the strong oxidizing properties of ozone. However, the reduction effect was subsequently counteracted by the granular activated carbon and chlorination units. This study provides basic data for ARG pollution in the drinking water system, and suggests that ARGs persist in drinking water, even after conventional chlorination or advanced treatment processes, highlighting the need for new and efficient water purification technologies.

Estimation of the Amount of Disposed Antibiotics

The impact of the antibiotics in the environment is not well understood yet. Moreover, the total amount of antibiotics that are ending up in the environment as solid waste is not known and cannot be rigorously determined as many variables are influencing the determination of their concentration. The present article is focused on the estimation of the amount of non-prescribed antibiotics that are used in different European countries. Particular attention is paid to the class of beta-lactams, as they are responsible for a considerate share of the antimicrobial resistance. The primary purpose was the estimation of the quantity of non-prescribed antibiotics that might reach the environment as solid waste. For the present study, we used the ECDC and EUROSTAT reported data.

Abundance and removal of antibiotic resistance genes (ARGs) in the rearing environments of intensive shrimp aquaculture in South China

Although research regarding antibiotic resistance genes (ARGs) in aquaculture environments has gained increasing scientific interest, further studies are required to understand the abundances and removal mechanisms of ARGs during the entire rearing period of shrimp aquaculture. Thus, in this study, abundances, distributions and removal rates of ARGs in different environmental compartments of intensive shrimp farms in South China were investigated during the entire rearing period. The results indicated that sul1 and cmlA were the predominant ARGs in the water and sediment samples. Additionally, the total abundance of ARGs was higher in shrimp pond water than in the source water and farm effluent. Moreover, sediment samples indicated significantly higher ARG abundances than water samples from the shrimp ponds (P < 0.05). Environmental factors were found to significantly affect the distribution of ARGs in shrimp rearing environments. Furthermore, stable ponds aided the removal of ARGs from shrimp pond water. This study accounted for temporal variations in ARG abundances as well as removal of ARGs in different environmental compartments during the entire shrimp rearing period. However, additional research is required to optimize the water treatment process for removal of ARGs from the aquaculture.

Seasonal Changes in Antibiotic Resistance Genes in Rivers and Reservoirs in South Korea

The fate of antibiotic resistance genes (ARGs) in aquatic environments, especially in rivers and reservoirs, is receiving growing attention in South Korea because reservoirs are an important source of drinking water in this country. Seasonal changes in the abundance of 11 ARGs and a mobile genetic element () in two reservoirs in South Korea, located near drinking water treatment plants in Cheonan and Cheongju cities, were monitored for 6 mo. In these drinking water sources, total ARG concentrations reached 2.5 × 10 copies mL, which is one order of magnitude higher than in influents of some wastewater treatment plants in South Korea. During the sampling periods in August, October, and November 2016 and January 2017, sulfonamides (), β-lactam antibiotics (), and tetracycline () resistance genes were the most abundant genes at the two sites. The ARG abundance consistently increased in January relative to 16S ribosomal ribonucleic acid (rRNA) counts. General stress responses to oxidative stress and other environmental factors associated with the cold season could be significant drivers of ARG horizontal gene transfer in the environment. Accordingly, removal of ARGs as a key step in water treatment warrants more attention.