Tetracycline Antibiotic Resistance Genes Research Articles

Characteristics of Microorganisms and Antibiotic Resistance Genes of the Riparian Soil in the Lanzhou Section of the Yellow River

Riparian soil is a critical area of watersheds. The characteristics of biological contaminants in riparian soil affect the pollution control of the watershed water environment. Thus, the microbial community structure, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) in the riparian soil of the Lanzhou section of the Yellow River were investigated by analyzing the characteristics of soil samples collected from farmland, mountains, and industrial land. The results showed that the Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant phyla in the riparian soil of Lanzhou section of the Yellow River. The microbial structure in the riparian soil was significantly correlated with the land use type (P < 0.05). The α diversity index of bacterial communities in land types was in the order of farmland > mountain > industry. Sulfonamide-typed ARGs were the most dominant genes in the soil of the Lanzhou section of the Yellow River Basin, among which the sul1 gene had the highest abundance, 20-36 000 times that of other detected ARGs. Moreover, the total absolute abundance of ARGs in industrial soil was the highest. Principal coordinate analysis (PCoA) displayed that the ARGs characteristics had a significant correlation with land types (P < 0.05), and intl1 and tnpA-04 drove the diffuseness of sulfonamide and tetracycline ARGs, respectively. Redundancy analysis (RDA) demonstrated that the content of inorganic salt ions and total phosphorus in the soil of the riparian zone of the Yellow River Lanzhou section were the main environmental factors, modifying the distribution of the microbial structure. Halobacterota and Acidobacteriota were the main microflora that drove the structural change in ARGs.

An Insight into the Exploration of Antibiotic Resistance Genes in Calorie Restricted Diet Fed Mice.

Antibiotic resistance genes (ARGs) threaten the success of modern drugs against multidrug resistant infections. ARGs can be transferred to opportunistic pathogens by horizontal gene transfer (HGT). Many studies have investigated the characteristics of ARGs in various chemical stressors. Studies on the effects of dietary nutrition and dietary patterns on ARGs are rare. The study first demonstrated the effect of calorie restricted (CR) diet on the ARGs and mobile genetic elements (MGEs) in mouse feces and explored their relationship with gut microbiota and their functions. The results showed that the abundance of the total ARGs in mouse feces of the CR group increased, especially tetracycline ARGs (tetW-01). The abundance of the MLSB ARGs (ermB) decreased evidently in mouse feces of the CR group. In addition, the total abundance of MGEs decreased evidently in the CR group, especially tnpA-03. In the meantime, the abundance of Lactobacillus and Bifidobacterium in mouse feces of the CR group increased remarkably. The Spearman correlation analysis between gut microbiota and ARGs showed that several probiotics were significantly positively correlated with ARGs (tetW-01), which might be the main contribution to the increase in ARGs of the CR group.

Combined effects of microplastics and chlortetracycline on the intestinal barrier, gut microbiota, and antibiotic resistome of Muscovy ducks (Cairina moschata)

Antibiotics and microplastics (MPs) have become critical concerns worldwide because of their increasing amount and ecological risks to ecosystems. However, how MPs exposure affects the bioaccumulation and risks of antibiotics in waterfowls remains poorly understood. In this study, Muscovy ducks were exposed to single and combined contamination with polystyrene MPs and chlortetracycline (CTC) for 56 days, and the effects of MPs on CTC bioaccumulation and their risks in duck intestines were investigated. MPs exposure reduced the bioaccumulation of CTC in the intestine and liver of ducks and increased their fecal CTC excretion. MPs exposure caused severe oxidative stress, inflammatory response, and intestinal barrier damages. Microbiome analysis showed that MPs exposure induced microbiota dysbiosis by increasing the abundance of Streptococcus and Helicobacter, the increase of which may exacerbate intestinal damages. Co-exposure to MPs and CTC alleviated the intestinal damage by regulating the gut microbiome. Metagenomic sequencing revealed that the combined exposure to MPs and CTC increased the abundance of Prevotella, Faecalibacterium, and Megamonas and incidence of total antibiotic resistance genes (ARGs), especially tetracycline ARGs subtypes in the gut microbiota. The results obtained herein provide new insights into the potential risks of polystyrene MPs and antibiotics in waterfowls living in aquatic environments.

The environmental risk of antibiotic resistance genes from manure compost fertilizer gradually diminished during ryegrass planting

As one of the emerging pollutants in the environment, antibiotic resistance genes (ARGs) have attracted much attention. Composting is an effective way to reduce ARGs and the compost products were often used as soil amendments. However, the environmental risk of ARGs from compost products to soil and plants has not been well studied. Here, we assessed the environmental risk of ARGs from soil and ryegrass after applying manure composting. This study detected 21 different types of ARGs. Multidrug and tetracycline resistance genes were the most dominant ones, accounting for 39.2%/12.5% and 38.6%/11.6% in soil/ryegrass, respectively. This might be attributed to the decrease of Streptomyces, which is the potential host of multidrug and tetracycline ARGs. The environmental risk value, which was associated with mobile genetic elements (MGEs) and pathogens, increased in the soil and ryegrass, and return to the original level at the end of the growth cycle. The absolute environmental risk values of AH (high additive amount of the swine manure compost) and BH (high additive amount of the sheep manure compost) decreased by 0.0826 and 0.1505, respectively. The outcomes of this study revealed the environmental behavior and risk of ARGs transferring from compost to soil, and then entering into ryegrass, which is important to assess the environmental risk of compost and provide new insights into agricultural food safety.

Nanoparticles and antibiotics stress proliferated antibiotic resistance genes in microalgae-bacteria symbiotic systems.

The comprehensive effect of exogenous pollutants on the dispersal and abundance of antibiotic-resistance genes (ARGs) in the phycosphere, bacterial community and algae-bacteria interaction remains poorly understood. We investigated community structure and abundance of ARGs in free-living (FL) and particle-attached (PA) bacteria in the phycosphere under nanoparticles (silver nanoparticles (AgNPs) and hematite nanoparticles (HemNPs)) and antibiotics (tetracycline and sulfadiazine) stress using high-throughput sequencing and real-time quantitative PCR. Meanwhile, the intrinsic connection of algae-bacteria interaction was explored by transcriptome and metabolome. The results showed that the relative abundance of sulfonamide and tetracycline ARGs in PA and FL bacteria increased 103-129 % and 112-134 %, respectively, under combined stress of nanoparticles and antibiotics. Antibiotics have a greater effect on ARGs than nanoparticles at environmentally relevant concentrations. Proteobacteria, Firmicutes, and Bacteroidetes, as the primary potential hosts of ARGs, were the dominant phyla. Lifestyle, i.e., PA and FL, significantly determined the abundance of ARGs and bacterial communities. Moreover, algae can provide bacteria with nutrients (carbohydrates and amino acids), and can also produce antibacterial substances (fatty acids). This algal-bacterial interaction may indirectly affect the distribution and abundance of ARGs. These findings provide new insights into the distribution and dispersal of ARGs in microalgae-bacteria symbiotic systems.

Co-occurrence of Tetracycline Antibiotic Resistance Genes and Microbial Communities in Plateau Wetlands Under the Influence of Human Activities

The widespread use of antibiotics has led to a large number of antibiotics entering the environment, to which microorganisms have become resistant. In recent years, with the intensification of human activities in the plateau region, the occurrence and migration of antibiotic resistance genes (ARGs) in plateau wetlands have attracted considerable attention. Here, we selected the Caohai National Wetland Park, located in the Yunnan-Guizhou Plateau, as our study area. The contents of tetracyclines, sulfonamides, quinolones, and macrolides in sediments from the upstream (the pristine habitat near the spring eye) and downstream (the sewage discharge outlet of residents) areas of the river in the park were analyzed. Among them, the detection content of tetracycline antibiotics was 103.65-2185 μg·kg-1, which was the highest antibiotic detection content. To further investigate the occurrence characteristics and influencing factors of tetracycline resistance genes, the influence of environmental factors, bacterial community structure, and pathogenic bacteria on tetracycline ARGs under the influence of human activities were revealed via correlation analysis and network analysis. The results showed that a total of 15 tetracycline resistance genes were detected in the upstream and downstream sediments. Among them, seven resistance genes including tetPA, tetD, and tetPB were detected in the upstream, and 13 resistance genes such as tetPA, tetE, tetM, and tetX were detected in the downstream. The abundance of eight new resistance genes in the downstream accounted for 43.44% of the downstream genes. The tetracycline-like antibiotics and soil physicochemical indicators (i.e., available phosphorus, total organic carbon, nitrate nitrogen, and total phosphorus) were the main environmental factors affecting the distribution of tetracycline ARGs. Additionally, the bacteria detected in the upstream and downstream sediments belonged to 64 bacterial phyla, among which Proteobacteria, Firmicutes, and Bacteroidota were the main phyla affecting the abundance of tetracycline ARGs; meanwhile, 27 pathogenic bacteria were detected in the upstream and downstream sediments. Network analysis showed that the correlation between the eight new resistance genes and pathogens in the downstream area accounted for 70% of the network connectivity, and Listeria monocytogenes, Enterococcus faecalis, and Bacteroides vulgatus were identified as potential hosts for the transmission of tetracycline ARGs. Compared to the pristine habitat, the discharge of domestic sewage introduced large amounts of antibiotics and also changed the microenvironment and microbial community structure of the river wetland. Additionally, it increased the species of ARGs in sediments, which promoted the spread and transmission of ARGs among microorganisms and even pathogens.

Sulfonamide and tetracycline resistance genes in nanjing lakes: effect of water quality and heavy metals

Due to high population density, anthropogenic activities and waste disposal have negatively affected artificial lakes in residential areas. These artificial lakes lack the capacity for auto-depuration to remove pollutants and contaminants; thus, they have the potential to act as reservoirs for antibiotic resistance genes (ARGs). In this study, we examined three urban artificial freshwater lakes in Nanjing to determine the abundance of sulfonamide and tetracycline resistance genes. Concerning water quality, the three lakes were found to be highly eutrophic, owing to their high levels of Total Nitrogen (TN), Phosphorous (TP), and Chlorophyll a (Chla). The average abundance of sulfonamide resistance genes detected in the three urban lakes was 42.446 log10 gene copies/100 ml, which was lower than the average abundance of tetracycline resistance genes (68.207 log10 gene copies/100 ml). Analysis by ANOVA revealed that all ARGs, except sul3, showed significant differences, probably due to varied anthropogenic influences in lakes. Pearson correlation and principal component analyses were performed to explore the correlation between ARGs, water quality markers, and heavy metals to understand the co-selection and drivers of ARGs propagation. tetM showed no correlation with any water quality markers, whereas Chla showed a positive correlation with all ARGs except tetM. tetM was the only gene observed to be unaffected by TN, TP, and Chla. The tet genes also showed strong associations with each other except tetM, especially tetA, tetQ, and tetG. The co-selection results between heavy metals and ARGs were insignificant (p > 0.05), with tetM being the most sensitive to the effects of heavy metals and As having the strongest effect on sul3 and tet genes. The results from this study provide basic but archival information on the effect of eutrophication and heavy metals such as Arsenic, showing the potential influence on the dissemination of certain sulfonamide and tetracycline ARGs in freshwater environments.

Response of Antibiotic Resistance Genes and Related Microorganisms to Arsenic during Vermicomposting of Cow Dung.

Antibiotic resistance pollution in livestock manure is a persistent issue that has drawn public attention. Vermicomposting is an ecofriendly biological process that can render livestock manure harmless and resourceful. However, little is known about the impact of vermicomposting on antibiotic resistance in livestock manure under stress caused by potentially toxic arsenic levels. Herein, lab-scale vermicomposting was performed to comprehensively evaluate the shift in antibiotic resistance genes (ARGs) and related microorganisms in fresh earthworm casts as well as vermicompost product health (i.e., nutrient availability and enzyme activity) when they were fed on arsenic-contaminated cow manure. The results showed that the earthworms' interaction with cow dung led to a significant reduction in ARG concentrations, especially for tetracycline ARGs (tet-ARGs), β-lactam ARGs (bla-ARGs), and quinolone ARGs (qnr-ARGs). However, arsenic significantly enhanced ARG accumulation in earthworm casts in a dose-dependent manner. Moreover, vermicomposting increased the percentage of Bacteroidota in the converted products. Furthermore, arsenic exposure at low concentrations promoted the proliferation of Proteobacteria, whereas high concentrations had little effect on Proteobacteria. Our study provides valuable insight into the changes in the antibiotic resistome and related microorganisms during vermicomposting of arsenic-amended cow manure, and it is crucial to explain the environmental impact of earthworms and improve our understanding of the reciprocal benefits of soil invertebrates.

Temperature-Responsive Nanocarrier-Regulated Alternative Release of "Cargos" for a Multiplex Photoelectrochemical Bioassay of Antibiotic-Resistant Genes.

A smart temperature stimuli-driven multiplex photoelectrochemical (PEC) assay was constructed for antibiotic resistance genes (ARGs) detection, where the stimuli-responsive gatekeeping by regulating the alternative release of "cargo" allowed for the simultaneous detection of multiple tetracycline resistance gene, using tetA (TDNA1) and tetC (TDNA2) as the model. Dual temperature-responsive nanoassemblies were embedded in the PEC bioassay as signal DNA tages: one thermoresponsive polymer (poly(N-isopropylacrylamide), PNIPAM)-capped mesoporous silica nanoparticles (MSN) with loading the "cargo" of HgO nanoparticles as signal DNA1 tags (SDNA1-PNIPAM@MSN@HgONPs) and the other antimony tartrate (SbT)-anchored silica nanospheres as signal DNA2 tags (SDNA2-SbT@SiO2NSs). At 20 °C, below the lower critical solution temperature (LCST) of PNIPAM, the "gatekeeper" PNIPAM in SDNA1-PNIPAM@MSN@HgONPs was in an ON state, igniting Hg2+ release through the pore of SiO2. While at above LCST (40 °C), it was in an OFF state. Likewise, the thermo-dependent dissociation of SbT endowed the grafted SDNA2 tags switching from the OFF (at 20 °C) to ON state (at 40 °C), igniting SbO+ release. The released Hg2+ and SbO+ triggered the amplified photocurrents due to the structure evolution of the photoactive layer into HgS/ZnS or Sb2S3/ZnS heterostructure, thus achieving sensitive detection of multiple ARGs: tetA, tetC, tetG, tetM, tetO, tetZ, tetX, and tetW. Combined with heat map analysis, rapid screening of the ARGs profiles in 12 samples could be realized. This bioassay is simple and accessible for multiple genes analysis with the detection limit down to 0.50 nM. And it was successfully applied for measuring tetracycline ARGs in real sludge samples.

β-lactamase genes transmission influenced by tetracycline, sulfonamide and β-lactams antibiotics contamination in the on-site farm soil

The prevalence of antibiotic resistance genes (ARGs), which have been identified as emerging environmental pollutants that pose a considerable risk to human health is widespread. The formation and transmission of ARGs are mainly associated with the antibiotic stress in an environment. And the abundance of ARGs also influenced by other categories antibiotics. The geographic information system was used to visualize the relative abundance of 28 types of ARGs and concentration of 18 types of antibiotics. The concentration of tetracycline antibiotics (TCs) and sulfonamide antibiotics (SAs) decreased gradually with increasing soil depth, while that of β-lactams (β-Ls) showed an increasing trend. The results revealed that TCs accounted for the largest proportion of all antibiotics. Furthermore, the abundance of β-lactam ARGs (β-RGs) increased with TCs and β-Ls increased. The abundance of tetracycline ARGs (TRGs) remained relatively stable with increasing concentrations of all antibiotics, while that of sulfonamide ARGs (SRGs) showed a decreasing trend. Although the abundance of β-RGs significantly increased with increasing levels of TCs and β-Ls. However, β-RGs were not significantly correlated with β-Ls, but with TCs. This study provided visual and comprehensive insights into the correlation between the distribution of typical antibiotics and ARGs and analyzed the synergy or antagonism between different antibiotics and ARGs. It is significant for soil remediation to reduce the likelihood of ARGs entering into and spreading in the human food chain via milk and beef consumption.

Hydrolyzation characteristics of waste actived sludge and antibiotics release when improved with alkyl polyglycoside

The purpose of this study was to find the optimal dosage of APG and initial pH to accelerate the hydrolysis of the waste activated sludge (WAS) and promote the release of antibiotics. In this study, the effects with APG dosage from 0.1 to 0.5 g/gSS and initial pH from 4.0 to 12.0 on WAS hydrolysis were investigated. Samples were regularly collected from different reaction conditions to determine SCODcr, protein, polysaccharide, antibiotics, antibiotic resistance genes (ARGs) and microbial diversity. The results showed that the combined action of APG+pH greatly promoted the solubilization of organic matter, and promoted the release of antibiotics. Compared with untreated sludge, when the optimal APG dosage was 0.3 g/gSS with pH 11.0 was combined, the release of organic matter was significantly increased, and the concentrations of the SCODcr, protein and polysaccharide reached 5650.4, 1386.4 and 794.2 mg/L, respectively within 2 h. At the same time, antibiotics (tetracyclines, sulfonamides, quinolones and macrolides) was also transferred from solid phase to liquid phase, among them roxithromycin (ROM) was 72.6 times higher than that in untreated control group, accordingly, the tetracycline ARGs tetB was 774.2 times higher than that in the control group. Meanwhile, APG greatly reduced the microbial diversity in the WAS samples, and greatly increased the relative abundance of proteobacteria, in which Gammaproteobacteria was the main microorganism.

Nanoscale polystyrene intensified the microbiome perturbation and antibiotic resistance genes enrichment in soil and Enchytraeus crypticus caused by tetracycline

Defined as plastic debris with size of 1–1000 nm, nanoplastics might be potentially more hazardous than plastics with larger size. However, current studies of nanoplastics in terrestrial systems are still limited, especially for the understanding of the combined effects of nanoplastics and antibiotics on microbiome and antibiotic resistance genes (ARGs) in soil invertebrates under the agricultural soil ecosystem is largely unknown. Here, we used Enchytraeus crypticus as model species to study the effects of nanoscale polystyrene and tetracycline. We found that co-exposure to nanoscale polystyrene and tetracycline not only significantly lowered the reproduction rate and increased the body weight of E. crypticus, but also significantly decreased the microbial alpha diversity and disturbed the beta diversity of microbiome in agricultural soil and E. crypticus. Nanoscale polystyrene had limited impacts on soil microbiota either at phylum level or family level but significantly disturbed the microbiome of E. crypticus. More specifically, NPs mainly decreased the relative proportion of rare taxa rather than the dominant phyla, including Acidobacteria (from 2.66% to 0.57%), Chloroflexi (from 1.43% to 0.21%), and Gemmatinomades (from 0.69% to 0.07%) in E. crypticus. Furthermore, synergistic effects for microbiome in soil and E. crypticus were found with nanoscale polystyrene and tetracycline. Meanwhile, nanoscale polystyrene enhanced the toxicity of tetracycline and promoted the enrichment of ARGs, such as multidrug ARGs in soil, and Vancomycin ARGs, Tetracycline ARGs, MLSB ARGs and Chloramphenicol ARGs in E. crypticus. These results add to our understanding of the combined effects of nanoplastics and antibiotics on the microbiome and ARGs of soil invertebrates.

Oh, deer! How worried should we be about the diversity and abundance of the faecal resistome of red deer?

The emergence of antimicrobial resistance (AMR) is a global threat to public health. Antimicrobials are used in animal production and human medicine, which contribute to the circulation of antibiotic resistance genes (ARGs) in the environment. Wildlife can be reservoirs of pathogens and resistant bacteria. Furthermore, anthropogenic pressure can influence their resistome. This work aimed to study the AMR of the faecal microbiome of red deer, one of the most important game species in Europe. To this end, a high-throughput qPCR approach was employed to screen a high number of ARGs and the antimicrobial susceptibility of indicator bacteria was determined. Several genes that confer resistance to different classes of antibiotics were identified, with the most abundant being tetracycline ARGs. Other genes were also present that are considered current and future threats to human health, and some of these were relatively abundant. Multidrug-resistant E. coli and Enterococcus spp. were isolated, although the overall level of antibiotic resistance was low. These results highlight the pressing need to know the origin and transmission of AMR in wildlife. Thus, and considering the One Health concept, studies such as this one shows the need for surveillance programs to prevent the spread of drug-resistant strains and ARGs.

Seasonal Variation and Influencing Factor Analysis of Antibiotic Resistance Genes in Water Supply Reservoirs of Central China

This study quantified an integron gene intI1 and 19 antibiotic resistance genes(ARGs) to identify the ARGs pollution characteristics in 11 drinking water reservoirs of central China. The results indicated that the ARGs abundance did not change significantly over time in the studied reservoir waterbodies. Tetracycline, sulfonamide, and β-lactam ARGs were dominant. The high abundance and detection rate of two sulfonamide ARGs(sul1 and sul2) suggested that they were the predominant ARGs. No polymyxin resistance genes(mcr-1) were detected, which indicated that the antibiotic restriction policy of China has achieved positive outcomes. Compared with that in other environmental media, the ARGs abundance in the reservoir environment was low. The correlation analysis showed relevance between the water quality indicators and the ARGs, which suggested that the water quality indexes can be used as ARGs pollution indicators in the reservoir environment. The abundance and detection rate of carbapenem ARGs were low owing to their dosage restriction and high degradability. Tetracycline ARGs were closely related to the other resistance gene types, which might have been due to horizontal gene transfer. Although the overall correlation between intI1 and ARGs was modest, it might be the main reason for the spread of several individual ARGs in the reservoir environment.

Metagenomics reveals the taxonomy and resistance mechanism of antibiotic resistance genes in bacterial communities of an aquaculture pond

In order to reveal the distribution characteristics of antibiotic resistance genes (ARGs) in freshwater aquaculture ponds, the microbial composition and antibiotic resistance gene types in the aquaculture environment were analyzed by using high-throughput and metagenomics sequencing technology. Our results showed that there were significant differences in the dominant bacteria composition in the water and sediment of aquaculture ponds. The dominant phylum in aquaculture water was Actinobacteria, Proteobacteria, Cyanobacteria and Bacteroidetes, while the phylum Actinobacteria, Chloroflexi and Proteobacteria were enriched in sediment. Compared with the comprehensive antibiotic research database (CARD), a total of 187 ARGs were identified, which were mainly multidrug, MLS and Tetracycline antibiotic resistance genes. There were 5 resistance mechanisms in the aquaculture environment, of which antibiotic efflux was the main resistance mechanism. Correlation analysis between ARGs and microbes showed that the abundance of Bacteroidetes, Cyanobacteria and Chloroflexi significantly affected the abundance of major resistance genes. This study is of great significance to protect the micro-environment of aquaculture ponds and control the pollution and spread of ARGs.

Distribution of Antibiotic Resistance Genes and Microbial Communities in a Fishery Reclamation Mining Subsidence Area

The widespread use of antibiotics in the aquaculture industry has caused antibiotic resistance genes (ARGs) pollution. Metagenomics technology was used to detect and analyze the relative abundance of ARGs and microbial community structure in a fishery reclamation mining subsidence area. A total of 29 ARGs were detected, and bacA had the highest relative abundance in all the samples, reaching 1.96×10-5-1.19×10-4. The relative abundance of sulfonamide and tetracycline ARGs in sediments was relatively high and the relative abundance of multidrug ARGs in well water was relatively high. Proteobacteria was the most dominant bacterial phylum in all the samples, and Chloroflexi and Euryarchaeota were relatively abundant in the sediments. Thiobacillus was the most dominant bacterial genus in the sediments, and Acinetobacter and Pseudomonas were the dominant bacterial genera in the well water. The correlation analysis between the ARGs and microorganisms showed that the genera and ARGs were mainly correlated to a moderate degree, and multiple genera had significant positive correlations with ARGs. The distribution of ARGs was affected by the structure of the microbial community. The sediments and well water in the fishery reclamation mining subsidence area were both contaminated by ARGs, and corresponding control measures should be strengthened to protect the regional environment.

PSXI-23 Prevalence of antibiotic resistance genes and bacterial community diversity from feces of pasture-raised broiler and layer chickens, swine, and beef cattle in the Southeastern USA

Abstract Animal manure can be a source of antibiotic resistant genes (ARGs) and pharmaceutical residues; however, few studies have been conducted to evaluate the presence of ARGs in pastured livestock systems. The objective was to determine the effects of four pasture-raised livestock species (broiler and layer chickens, swine, and beef cattle) on three different farms on fecal antibiotic residues (AR), microbial community diversity (MCD), and ARGs. Fecal DNA was collected (25 g each), homogenized, and extracted (0.2 g) using a Fecal/Soil Microbe DNA MimiPrep Kit. 16S rRNA, an estimate of the total MCD, was sequenced. Sulfonamide (Sul; Sul1) and tetracycline (Tet; TetA) ARGs were enumerated by qPCR. The results indicated that average fecal Tet AR tended to be greater (P = 0.09) for broiler chickens (11.4 µg kg-1) than for other livestock species (1.8-0.06 µg kg1), while chlortetracycline, lincomycine, oxytetracycline, and sulfachloropyridazine AR were similar among livestock species. There were interactions (P < 0.01) between farms and animal species for fecal pH and concentrations of total carbon, magnesium, sulfur, copper, and lead across animal species. In addition, cattle and swine samples showed a high degree of variability (α- and □-diversities) in fecal MCD, compared to broiler and layer fecal samples (P < 0.01). Firmicutes were the most abundant bacterial phylum in broiler (85.3%) and layer (80.0%) chickens (P < 0.01), as compared to swine (64.4%) and cattle (62.1%). The Sul1 (P < 0.05) and TetA (P < 0.001) ARGs in layer hens were the highest (16.5 x 10–4 and 1.4 x 10–4), followed by broiler chickens (2.9 x 10–4 and 1.7 x 10–4), swine (0.22 x 10–4 and 0.20 x 10–4), and beef cattle (0.19 x 10–4 and 0.02 x 10–4). This study indicated that individual farm management practices and specific animal species affected content of fecal AR, the fecal MCD, and ARG status in pasture-raised animals.

Distribution patterns of antibiotic resistance genes and their bacterial hosts in pig farm wastewater treatment systems and soil fertilized with pig manure

Vast reservoirs of antibiotic resistance genes (ARG) are discharged into the environment via pig manure. We used metagenomic analysis to follow the distribution and shifts of ARGs and their bacterial hosts along wastewater treatment in three large pig farms. The predominating ARGs potentially encoded resistance to tetracycline (28.13%), aminoglycosides (23.64%), macrolide-lincosamide-streptogramin (MLS) (12.17%), sulfonamides (11.53%), multidrug (8.74%) and chloramphenicol (6.18%). The total relative ARG abundance increased along the treatment pathway prior to anaerobic digestion that had a similar degradative capacity for different ARGs and these ARGs were reduced by about 25% after digestion, but ARGs enriched erratically in manured soils. Distinctive ARG distribution patterns were found according to the three sample locations; feces, soil and wastewater and the differences were primarily due to the tetracycline ARGs (feces > wastewater > soil), sulfonamide ARGs (soil > wastewater > feces) and MLS ARGs (feces > wastewater > soil). Metagenomic assembly-based host analyses indicated the Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes were primary ARG carriers. The Streptococcaceae increased the abundance of multidrug, MLS and aminoglycoside ARGs in feces; Moraxellaceae were the primary contributors to the high abundance of multidrug ARGs in wastewater; the Comamonadaceae led to the higher abundance of bacA in wastewater and soil than feces. We found a high level of heterogeneity for both ARGs and ARG-hosts in the wastewater treatment system and in the agricultural soils for these pig farms.

Differences in Tetracycline Antibiotic Resistance Genes and Microbial Community Structure During Aerobic Composting and Anaerobic Digestion.

Antibiotics are widely added to swine forage and are the main reason for the environmental accumulation of antibiotic resistance genes (ARGs) in swine manure-dwelling microorganisms. Aerobic composting (AC) and anaerobic digestion (AD) are efficient methods for converting swine manure to bio-fertilizer while degrading residual antibiotics. However, the influence of these methods on ARG accumulation and the difference in their efficiency have rarely been investigated. In this study, we explored the variations in four tetracycline antibiotics (TCs) and their associated ARGs and in microbial communities after AC and AD treatment. After full-scale manure AC and AD, the four TCs were removed effectively. AD had a higher TC removal efficiency than AC and a slower rate of TC-associated ARG accumulation. In addition, the community structure was more stable in the AC and AD manures than in untreated manure, and the relationship among microbial species also evolved into competition from mutualism after both AC and AD treatment. It was also speculated that the genera Acholeplasma and Arthrobacter were the possible hosts of tetO, tetW, and tetQ; the shift in the prokaryotic community composition and the alleviation of selective pressure by TC degradation led to decreased relative abundance of ARGs in AD- and AC-treated manure.

Struvite crystallization induced the discrepant transports of antibiotics and antibiotic resistance genes in phosphorus recovery from swine wastewater

Struvite (MgNH4PO3·6H2O) crystallization is one of important methods of phosphorus recovery from wastewater. As to livestock wastewater, the high-strength occurrence of antibiotics and antibiotic resistance genes might induce struvite recovery to spread antibiotic resistance to the environment. However, limited information has been reported on the simultaneous transport of antibiotics and ARGs in struvite recovery. In the present study, tetracyclines (TCs) and tetracyclines antibiotic resistance genes (ARGs) were selected as the targeted pollutants, and their discrepant residues in struvite recovery from swine wastewater were investigated. TCs and ARGs were obviously detected, with their contents of 4.88–79.5 mg/kg and 6.99 × 107–2.14 × 1011 copies/g, notably higher than those of TCs 0.550–1.94 mg/kg and ARGs 3.98 × 104–5.66 × 107 copies/g obtained from synthetic wastewater. The correlational relationship revealed that predominant factors affecting TCs and ARGs transports were different. Results from network analyses indicated that among the total edges, the negative correlations between TCs and ARGs predominately occupied 18.0%. The redundancy analysis revealed that mineral components in the recovered products, including struvite, K-struvite and amorphous calcium phosphate, coupling with organic contents, displayed insignificant roles on TCs residues, where heavy metals exerted positive and remarkable functions to boost TCs migration. Unexpectedly, mineral components and heavy metals did not displayed significant promotion on ARGs transport as a whole.