Co-localization of antibiotic resistance genes is widespread in the infant gut microbiome and associates with an immature gut microbial composition

BACKGROUND

In environmental bacteria, the selective advantage of antibiotic resistance genes (ARGs) can be increased through co-localization with genes such as other ARGs, biocide resistance genes, metal resistance genes, and virulence genes (VGs). The gut microbiome of infants has been shown to contain numerous ARGs, however, co-localization related to ARGs is unknown during early life despite frequent exposures to biocides and metals from an early age.

RESULTS

We conducted a comprehensive analysis of genetic co-localization of resistance genes in a cohort of 662 Danish children and examined the association between such co-localization and environmental factors as well as gut microbial maturation. Our study showed that co-localization of ARGs with other resistance and virulence genes is common in the early gut microbiome and is associated with gut bacteria that are indicative of low maturity. Statistical models showed that co-localization occurred mainly in the phylum Proteobacteria independent of high ARG content and contig length. We evaluated the stochasticity of co-localization occurrence using enrichment scores. The most common forms of co-localization involved tetracycline and fluoroquinolone resistance genes, and, on plasmids, co-localization predominantly occurred in the form of class 1 integrons. Antibiotic use caused a short-term increase in mobile ARGs, while non-mobile ARGs showed no significant change. Finally, we found that a high abundance of VGs was associated with low gut microbial maturity and that VGs showed even higher potential for mobility than ARGs.

CONCLUSIONS

We found that the phenomenon of co-localization between ARGs and other resistance and VGs was prevalent in the gut at the beginning of life. It reveals the diversity that sustains antibiotic resistance and therefore indirectly emphasizes the need to apply caution in the use of antimicrobial agents in clinical practice, animal husbandry, and daily life to mitigate the escalation of resistance. Video Abstract.

Occurrence and distribution of antibiotics and antibiotic resistance genes from the land to ocean in Daliao River-Liaodong Bay, China

In this study, the pollution status of antibiotics and ARGs in sediments from the land-sea intersection of Liaodong Bay was analyzed. The results showed that the level of antibiotic pollution ranged from ND to 433.27 ng/kg, with quinolones and tetracycline as the dominant antibiotics. The relative abundance of ARGs ranged from 3.62 × 10-3 to 1.32 × 10-1 copies/16SrRNA copies, with aminoglycoside and MLSB resistance genes being dominant. Regarding spatial distribution, the land and estuary areas showed higher antibiotic pollution levels than the offshore areas. Similarly, the land and estuary areas exhibited higher antibiotic diversity than the offshore areas. The ARGs were widely distributed on land, and their abundance gradually decreased to the downstream estuary area. Land and coastal areas exhibited higher ARG diversity than estuary areas. Analysis of environmental factors revealed a significant correlation between ARGs and non-corresponding antibiotics, and some ARGs were affected by heavy metals Cu and Pb.

Genomic characterization of extended spectrum beta lactamases producing multidrug-resistant Escherichia coli clinically isolated harboring chromosomally mediated CTX-M-15 from Alkharj, KSA

Extended Spectrum Beta Lactamases (ESBLs) are the most prevalent enzymes conferring resistance to beta-lactams encoded on plasmids and rarely in chromosomes. This genomic study aims to characterize Escherichia coli to identify antimicrobial resistance genes (ARG), virulence factors, and phylogenetic relationships among ESBL-positive and negative isolates of E. coli obtained from Al-Kharj, Riyadh region, Saudi Arabia. Three clinical isolates from urine and vaginal swabs were obtained and subjected to whole genome sequencing, minimum inhibitory concentration, and antibiotic sensitivity tests. The pathogenicity and ARG were discovered, and the raw genomic sequences were assembled and annotated. Two isolates (E5 and E15) were MDR and ESBLs producers; the sequence type (ST) for E5 was 58, while those for E15 and E21 were 106. Most of the virulence genes were detected as plasmid-mediated; E21 was identified with a hyper-virulent plasmid (pH 2332-166) carrying different virulence factors (TraJ, traT, iss, etsC, hlyF, and iron acquisition associated proteins), plasmids (IncFII, IncFIB, and IncFIA), and insertion sequences (ISEc31). While most of the antimicrobial resistance genes were chromosomally mediated, a rare chromosome insertion of qnrS1 and blaCTX-M-15 with co-occurrence of Tn2 and ISKpn19 was identified in the E5 isolate. The consistent preservation of these genetic elements on bacterial chromosomes and plasmids could enhance the spread of Multidrug-Resistant (MDR) strains across various Enterobacteriaceae Species. This poses a significant threat to the effectiveness of existing antimicrobial treatments.

Oil-contaminated sites act as high-risk pathogen reservoirs previously overlooked in coastal zones

In addition to the organic pollutants and disturbance to the microbial, plant and animal systems, oil contamination can also enrich opportunistic pathogens. But little is known about whether and how the most common coastal oil-contaminated water bodies act as reservoirs for pathogens. Here, we delved into the characteristics of pathogenic bacteria in coastal zones by constructing seawater-based microcosms with diesel oil as a pollutant. 16S rRNA gene full-length sequencing and genomic exploration revealed that pathogenic bacteria with genes involved in alkane or aromatic degradation were significantly enriched under oil contamination, providing a genetic basis for them to thrive in oil-contaminated seawater. Moreover, high-throughput qPCR assays showed an increased abundance of the virulence gene and enrichment in antibiotics resistance genes (ARGs), especially those related to multidrug resistance efflux pumps, and their high relevance to Pseudomonas, enabling this genus to achieve high levels of pathogenicity and environmental adaptation. More importantly, infection experiments with a culturable P. aeruginosa strain isolated from an oil-contaminated microcosm provided clear evidence that the environmental strain was pathogenic to grass carp (Ctenopharyngodon idellus), and the highest lethality rate was found in the oil pollutant treatment, demonstrating the synergistic effect of toxic oil pollutants and pathogens on infected fish. A global genomic investigation then revealed that diverse environmental pathogenic bacteria with oil degradation potential are widely distributed in marine environments, especially in coastal zones, suggesting extensive pathogenic reservoir risks in oil-contaminated sites. Overall, the study uncovered a hidden microbial risk, showing that oil-contaminated seawater could be a high-risk pathogen reservoir, and provides new insights and potential targets for environmental risk assessment and control.

Fecal antibiotic resistance genes were transferred through the distribution of soil-lettuce-snail food chain

Massive antibiotic resistance genes (ARG) were detected in the soil modified by manure, which may affect human life safety through the food chain. However, the transmission of ARGs through the soil-plant-animal food chain is still unclear. Therefore, this study used high-throughput quantitative PCR technology to explore the effects of pig manure application on ARGs and bacterial communities in soil, lettuce phyllosphere, and snail excrement. The results showed that a total of 384 ARGs and 48 MEGs were detected in all samples after 75 days of incubation. The diversity of ARGs and MGEs in soil components increased significantly by 87.04% and 40% with the addition of pig manure. The absolute abundance of ARGs in the phyllosphere of lettuce was significantly higher than that of the control group, with a growth rate of 212.5%. Six common ARGs were detected between the three components of the fertilization group, indicating that there was internal transmission of fecal ARGs between the trophic levels of the food chain. Firmicutes and Proteobacteria were identified as the dominant host bacteria in the food chain system, which were more likely to be used as carriers of ARGs to promote the spread of resistance in the food chain. The results were used to assess the potential ecological risks of livestock and poultry manure. It provides theoretical basis and scientific support for the formulation of ARG prevention and control policies.

P, N, and C-related functional genes in SBR system promoted antibiotics resistance gene transmission under polystyrene microplastics stress

Wastewater treatment plants (WWTPs) are important sinks of microplastics (MPs) and antibiotics resistance genes (ARGs). Information regarding connections between functional modules of WWTPs and spread of ARGs under MPs stress is still lacking. In this study, correlations between P-, N-, and C-related functional genes and ARGs in a sequencing batch reactor (SBR) system were evaluated under polystyrene (PS) MPs stress. Total P and chemical oxygen demand (COD) in effluent showed no significant changes under 0.5-50 mg L^-1 PS MPs stress within 32 cycle treatment periods of SBR, while 0.5 mg L^-1 PS MPs affected the N cycling process. PS MPs (0.5-50 mg L^-1) promoted the richness and diversity of microbial community in SBR, and the denitrification process was exuberant. PS MPs with a low dosage (0.5-5 mg L^-1) enhanced secretion of extracellular polymeric substances and promoted expression levels of functional genes related to C fixation, C degradation, P cycling, and N cycling. Simultaneously, aac(3)-II, bla_TEM-1, and tetW increased by 27.13%, 38.36%, and 9.57% under low dosages of PS MPs stress; more importantly, the total absolute abundance of intI1 nearly doubled. 78.4% of these P-, N-, and C-related functional genes were positively correlated with intI1, thus favoring transmission of ARGs. This study firstly disclosed the underlying correlations between functional modules of WWTPs and spread of ARGs under MPs stress.

A comprehensive study of the source, occurrence, and spatio-seasonal dynamics of 12 target antibiotics and their potential risks in a cold semi-arid catchment

Antibiotics are widely consumed and are ubiquitous in aquatic ecosystems, such as in agricultural and fishery lake catchments, for prophylactic treatment. However, there are very few comprehensive studies reporting all seasonal occurrences, spatiotemporal dynamics, and risk assessments of antibiotics in agricultural lake catchments, especially in cold regions during the winter season. This study measured seasonality in the concentrations of 12 antibiotics belonging to seven different classes in the surface waters (tributary rivers and lakes) of the Chagan lake catchment in northeast China. All antibiotics were detected in most of the water samples across most seasons, with concentrations varying for different compounds, locations, and seasons. These levels were discussed in terms of the main sources at different sampling sites, including agriculture, fish farming, municipal wastewater, and others. In general, the highest concentrations of most compounds were observed during the freeze-thaw periods. The number of antibiotic resistance genes (ARGs) correlated with compound lipophilicity and half-life. Based on the ecological risks of antibiotics and the relative abundance of ARGs, a hierarchical control priority list (HCPL) of antibiotics was determined, considering four levels (critical, high, medium, and low). To further strengthen the control and effectively manage antibiotics, we highly recommend the reduction and selective use of veterinary antibiotics in winter and spring during the freeze-thaw periods in the Chagan lake catchment.

Algal-bacterial consortium mediated system offers effective removal of nitrogen nutrients and antibiotic resistance genes

The sulfonamide antibiotic resistance genes (ARGs) especially sul1 was identified as the dominant in eutrophic water. The performance of Chlorella vulgaris-B. licheniformis consortium toward sul1 removal, total nitrogen (TN) removal, and the mechanism of sul1 removal was investigated. The removal efficiency of exogenous ARGs plasmids carrying sul1 reached (97.2 ± 2.3)%. The TN removal rate reached (98.5 ± 1.2)%. The enhancements of carbon metabolism, nitrogen metabolism, aminoacyl-tRNA biosynthesis, and glycoproteins had significant influences on sul1 and TN removals, under the premise of normal growth of algae and bacteria. The quantitative polymerase chain reaction (qPCR) results suggested that the absolute abundances of sul1 were low in algal-bacterial systems (0 gene copies/mL) compared with individual systems ((1 × 10⁶ ± 15) gene copies/mL). The duplication of sul1 was inhibited in algal cells and bacterial cells. The algal-bacterial consortium seems to be a promising technology for wastewater treatment with a potential to overcome the eutrophication and ARGs challenges.

Increasing the removal efficiency of antibiotic resistance through anaerobic digestion with free nitrous acid pretreatment

Swine manure is a significant reservoir for antibiotic resistance. Anaerobic digestion (AD) is a common biological process used to treat swine manure but still faces low efficiencies in biogas production and antibiotic resistance removal. It is here shown that AD with free nitrous acid pretreatment (FNA) was effective in reducing antibiotic resistance genes (ARGs) in swine manure. FNA pretreatment (nitrite =250 mg N/L, pH=5.0, temperature=20 ± 1 °C) simultaneously reduced antibiotics (Tetracyclines, Quinones and Sulfonamides), inactivated antibiotics resistance bacteria (ARB) by 0.5-3 logs, and decreased ARGs tet, sul and qnr by 1-2, 1-3 and 0.5 logs, respectively. In the following AD step, the total residual ARGs was reduced to ~3.49 × 10⁷ gene copies/g dry total solids (TS), ~1 log lower than that in the AD without pretreatment (3.55 ×10⁸ gene copies/g dry TS). Microbial community and network analyses revealed that the ARG removal was mainly driven by the direct FNA effect on reducing ARGs and antibiotics, not related to ARB. Besides, the FNA pretreatment doubled biochemical methane production potential from swine manure. Together these results demonstrate that AD with FNA pretreatment is a useful process greatly facilitating swine manure management.

A review on antibiotics removal: Leveraging the combination of grey and green techniques

Antibiotics are currently a major source of concern around the world due to the serious risks posed to human health and the environment. The performance of the secondary wastewater treatment processes/technologies (representing grey process) and constructed wetlands (CWs) (typical green process) in removing antibiotics and antibiotic resistance genes (ARG) was reviewed. The result showed that the grey process mainly removes antibiotics, but does not significantly remove ARG, and some processes may even cause ARG enrichment. The overall treatment in CWs is better than WWTPs, especially for ARG. Vertical subsurface flow CWs (VFCWs) are more conductive to antibiotics removal, while horizontal subsurface flow CWs (HFCWs) have a better ARG removal. More importantly, this review admits and suggests that the combination of grey process with green process is an effective strategy to remove antibiotics and ARG. The most advantage of the combination lies in realizing complementary advantages, i.e. the grey process as the primary treatment while CWs as the polishing stage. The efficiency of such the hybrid system is much higher than either single treatment process.

Influence of site-specific factors on antibiotic resistance in agricultural soils of Yangtze River Delta: An integrated study of multi-factor modeling

Agricultural soils are important reservoirs for antibiotic resistance genes (ARGs), which is closely linked to soil microorganisms. Environmental factors and co-existed pollutants may function as promoters or inhibitors for ARG proliferation to influence the agriculture green development. However, research focusing on the interaction of potential environmental drivers and ARGs is still lacking in agricultural soils. Here, we explored the microbial profile in 241 soil samples in Yangtze River Delta, and analyzed the relationship of microbial structures, ARGs, and typical site-specific factors. We found that the abundance of most ARGs was negatively correlated with the ratio of fungi and bacteria (F/B), whereas positively correlated with the ratio of gram-positive and gram-negative microbes (G⁺/G^-). The co-occurrence network revealed significant associations among 18 site-specific factors, including 6 meteorological factors, 5 soil physicochemical properties, 5 co-existed organic pollutants, and 2 co-existed heavy metals. Random forest analysis demonstrated that F/B was mainly influenced by soil organic matters and co-existed polychlorinated biphenyls, while G⁺/G^- was predominately regulated by soil total phosphorus and moisture content, which possibly resulting in their difference relationship with ARG abundance. Besides, the contribution of meteorological factors (>30%) in the explanation for F/B and G⁺/G^- structures was the highest among all the site-specific factors. Together with path analysis showing meteorological factors probably affecting the ARG abundance through direct positive ways or indirect paths via physicochemical properties, microbial structure, and co-existed organic pollutants, we considered meteorological factors as the potential promoters for ARG proliferation. Collectively, these results increase our understanding of agricultural soils as hotspots of ARGs, and highlight the underappreciated role of meteorological factors as potential promoters for soil ARGs, providing reference for us to regulate ARG pollution scientifically to improve the development of green agriculture.

Simultaneous elimination of antibiotics and antibiotics resistance genes in nitritation of source-separated urine

Antibiotics in human urine could accelerate dissemination of antibiotics resistance genes (ARGs), posing potential threat to sewage. The nitritation of source-separated urine was a critical step to realize the urine resourcelization and nitrogen stabilization. However, the synergic control on antibiotics and ARGs during urine nitritation was unrevealed. This study investigated the removal profiles of five typical antibiotics and the shifts of microbial community and ARGs during stable nitritation. The result showed that sulfamethoxazole and roxithromycin were effectively eliminated with high removal efficiency of (95 ± 5) % and (90 ± 10) %, followed by enrofloxacin with removal efficiency of (60 ± 5) %, whereas trimethoprim and chloramphenicol showed low removal efficiency of less than 40 %. Ammonia oxidation bacteria and heterotrophic bacteria equally contributed to elimination of sulfamethoxazole with a high biodegradation rate of 0.1534 L/gVSS·h, while sorption and biodegradation jointly promoted other antibiotics removal. The total relative abundance of top 25 bacteria genera was decreased by 10 %. The total relative abundance of top 30 ARGs was decreased by more than 20 %, which was corresponding to the variation of bacterial community. The findings in this research would get a deeper insight into the eliminating antibiotics and controlling ARGs dissemination during nitritation of source-separated urine.

Effect of tetracycline on bio-electrochemically assisted anaerobic methanogenic systems: Process performance, microbial community structure, and functional genes

Bio-electrochemically assisted anaerobic methanogenic systems (An-BES) are highly effective in wastewater treatment for methane production and degradation of toxic compounds. However, information on the treatment of antibiotic-bearing wastewater in An-BES is still very limited. This study therefore investigated the effect of tetracycline (TC) on the performance, microbial community, as well as functional and antibiotic resistance genes of An-BES. TC at 1 and 5 mg/L inhibited methane production by less than 4.8% compared to the TC-free control. At 10 mg/L TC, application of 0.5 and 1.0 V decreased methane production by 14 and 9.6%, respectively. Under the effect of 1-10 mg/L TC, application of 1.0 V resulted in a decrease of current from 42.3 to 2.8 mA. TC was mainly removed by adsorption; its removal extent increased by 19.5 and 32.9% with application of 0.5 and 1.0 V, respectively. At 1.0 V, current output was not recovered with the addition of granular activated carbon, which completely removed TC by adsorption. Metagenomic analysis showed that propionate oxidizing bacteria and methanogens were more abundant in electrode biofilms than in suspended culture. Antibiotic resistance genes (ARGs) were less abundant in biofilms than in suspended culture, regardless of whether voltage was applied or not. Application of 1.0 V resulted in the enrichment of Geobacter in the anode and Methanobacterium in the cathode. TC inhibited exoelectrogens, propionate oxidizing bacteria, and the methylmalonyl CoA pathway, leading to a decrease of current output, COD consumption, and methane production. These findings deepen our understanding of the inhibitory effect of TC in An-BES towards efficient bioenergy recovery from antibiotic-bearing wastewater, as well as the response of functional microorganisms to TC in such systems.

Systematic review and meta-analysis of environmental Vibrio species - antibiotic resistance

Adequate comprehension of the genomics of microbial resistance to an antimicrobial agent will advance knowledge on the management of associated pathologies and public health safety. However, continued emergences and reemergence of pathogens, including Vibrio species, hallmarks a potential knowledge gap. A clear understanding of the process and forecast of the next trend should be in place to nip in the bud, microbial acquisition of resistance to antibiotics. Therefore, this two-decade (1 January 2000 to 31 December 2019) systematic review and meta-analytical study articulated the prevalence and incidence of antibiotics resistance genes in Vibrio species isolated from environmental samples. Articles from the Web of Science and PubMed electronic databases was engaged. Heterogeneity of the data and bias were analyzed with random effect model meta-analysis and funnel plot. A total of 1920 Vibrio sp. were reported by the ten selected articles included in this study; out of which 32.39% of identified isolates displayed antimicrobial resistance and associated genes. The distribution of antibiotics resistance genes in Vibrio sp., reported within six countries was 21% tetracycline (tet), and 20% sulphonamide (sul) and β-lactamase (bla) respectively. The quinolone, tetracycline and sulfonamide resistance genes showed 32.97% (95% CI 0.18–0.53) prevalence while chloramphenicol, macrolides and aminoglycoside resistance genes are expressed in percentages as 28.67% (95% CI 0.15–0.47) and β-lactamase resistance genes 27.93% (95% CI 0.11–0.56) respectively. The Vibrio antibiotics resistance genes (V-ARG) distribution depicts no regular trend or pattern from the analyzed data. Consequently, more studies would be required to articulate the structure of cohesion in the distribution of the resistance determinants in microbes.

A new insight into the ARG association with antibiotics and non-antibiotic agents-antibiotic resistance and toxicity

Although concerns have been raised about co-selection for antibiotic resistance and various antibiotics and non-antibiotic agents, the data on their association in urban sludge is still limited. In addition, antibiotic contamination can result in not only the toxicity but also the antibiotic resistance. In this study, the first large-scale identification of antibiotics and non-antibiotic agents concern for co-selection of resistance against antibiotics was conducted in urban sludge. Co-occurrence analysis showed that antibiotic resistance genes (ARGs) had no significant correlation with the corresponding antibiotics. Therefore, the results of co-occurrence analysis based on antibiotic concentration and ARG abundance were always ambiguous and difficult to interpret. However, antibiotic resistance was positively correlated with highly toxic compounds such as diclofenac, enrofloxacin and nicotine, suggesting that environmental contaminants might influence antibiotic resistance while exerting toxicity through mechanisms such as changes in microbial community and enzyme activity. The close correlation between class 1 integrase gene (intI1) and diclofenac/enrofloxacin indicated that the co-selection scenario between environmental contaminants and ARGs was likely mediated via intI1. In total, the derived co-occurrence patterns improve our understanding of the co-selection between ARGs, antibiotics and non-antibiotic agents, and also reaffirm the importance of potential role of non-antibiotic agents in the global spread of antibiotic resistance.

The key environmental influencing factors for the change of sediment bacterial community and antibiotics resistance genes in a long-term polluted lake, China

In order to investigate the key environmental influencing factors for the change of sediment bacterial community structure (BCS) and antibiotics resistance genes (ARGs) in a long-term Quinolone antibiotics (QNs) and heavy metals (HMs) polluted lake, 16S rRNA MiSeq High-throughput Sequencing and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis methods were applied. Baiyangdian lake was subdivided into three habitats: (1) Habitat 1: greatly influenced by municipal wastewater; (2) Habitat 2: mainly impacted by aquaculture sewage and domestic wastewater; and (3) Habitat 3: with the least human activities. Through One-way ANOVA analysis, the results showed that most of QNs and HMs showed significant difference among three habitats. Both the highest richness and diversity indices of bacterial community appeared in Habitat 3. The abundance of Multidrug, Phenicol, Aminoglycoside, Teracycline, and Quinolone ARGs exhibited the highest values in Habitat 1, while the abundance of Macrolide-Lincosamide-Streptogramin (MLS), Rifamycinm, and Sulfonamide ARGs appeared the highest values in Habitat 2. The result of redundancy analysis exhibited that 68.8% and 93.8% of the change in BCS and ARGs can be explained by environmental factors, respectively. Pb (explained 37.5% (p = 0.002)) and Fleroxacin (FLE) (explained 51.3% (p = 0.026)) were the most important factors for the variation of BCS and ARGs, respectively. Therefore, the effects of antibiotics and HMs on BCS and ARGs should be simultaneously paid more attention. Furthermore, the ARGs results by PICRUSt were similar to the results by metagenomic shotgun sequencing analysis, thus the PICRUSt analysis method can be used in the future research.

Distribution of antibiotic resistance genes in the environment

The prevalence of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the microbiome is a major public health concern globally. Many habitats in the environment are under threat due to excessive use of antibiotics and evolutionary changes occurring in the resistome. ARB and ARGs from farms, cities and hospitals, wastewater treatment plants (WWTPs) or as water runoffs, may accumulate in water, soil, and air. We present a global picture of the resistome by examining ARG-related papers retrieved from PubMed and published in the last 30 years (1990-2020). Natural Language Processing (NLP) was used to retrieve 496,640 papers, out of which 9374 passed the filtering test and were further analyzed to determine the distribution and diversity of ARG subtypes. The papers revealed seven major antibiotic families together with their respective ARG subtypes in different habitats on six continents. Asia, especially China, had the highest number of ARGs related papers compared to other countries/regions/continents. ARGs belonging to multidrug, glycopeptide, and β-lactam families were the most common in reports from hospitals and sulfonamide and tetracycline families were common in reports from farms, WWTPs, water and soil. We also highlight the 'omics' tools used in resistome research, describe some factors that shape the development of resistome, and suggest future work needed to better understand the resistome. The goal was to show the global nature of ARB and ARGs in order to encourage collaborate research efforts aimed at reducing the negative impacts of antibiotic resistance on the One Health concept.

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.

Soil oxytetracycline exposure alters the microbial community and enhances the abundance of antibiotic resistance genes in the gut of Enchytraeus crypticus

Gut microbiota make an important contribution to the health of soil invertebrates. Many studies have focused on effects of antibiotics on soil invertebrates. Influence from antibiotics on the gut microbiota of non-target soil fauna is rarely reported and the abundance of antibiotics resistance genes (ARGs) in the gut is poorly understood. Here, 10 μg·g^-1 of oxytetracycline (OTC) (environmentally relevant concentration) was added in soil, used Enchytraeus crypticus as soil model worm was tested for the response to oxytetracycline. The results showed that although soil OTC exposure did not cause a change in E. crypticus growth, mortality or reproduction, it did result in bioaccumulation of OTC in E. crypticus body tissues. The OTC treatment induced a shift in the composition and diversity of the gut microbiota of E. crypticus when compared to the control treatment. Specifically, the relative abundance of Proteobacteria declined significantly from 52.2% to 32.4% after OTC exposure (P = 0.028), but the relative abundance of Planctomycetes was significantly elevated from 28.1% to 45.8% (P = 0.002). It is noteworthy that soil OTC exposure significantly enhanced the abundance and number of tetracycline-related ARGs in the E. crypticus gut. These results suggest that change in E. crypticus gut microbiota has potential as an indicator of soil antibiotic pollution, and E. crypticus gut may act as a receiver and mediator of ARGs resulting from soil antibiotic pollution.

Urban and agriculturally influenced water contribute differently to the spread of antibiotic resistance genes in a mega-city river network

The widespread of water borne antibiotic resistance genes (ARGs) represents a growing threat to the health of millions of people. Our study detected the relative abundances of 10 ARG subtypes in the Shanghai river network, where the major ARG components were strB, sul1, and ermB. These ARGs were significantly enriched by the combined sewage, tail water from urban wastewater treatment plant and runoff from agricultural areas, which reached the Suzhou (SZ), Dianpu (DP), and Huangpu (HP) River, respectively (one-way ANOVA, P < 0.01). The target ARGs were distributed in varying patterns across different rivers. bla_CTX-M and bla_TEM contributed to the increase of total ARGs in the rivers influenced by urban sources, particularly in the SZ River, whose distribution of ARGs was significantly related to that of the confluence of the whole river network (Mantel test, P < 0.01). The bacterial community was closely structured with ARGs and potential pathogenic bacteria's association with target ARGs became significant in downstream samples (Procrustes test, P = 0.03). Water near urban wastewater fallouts was observed to have the highest content of intl1 in the DP River, whose downstream samples' intl -ARG relationship fitted the same regression model as that of the network confluence (R = 0.84, P < 0.001). The amelioration of river water quality does not reduce ARGs, but may affect their distributional patterns in the river network in Shanghai.

Simulated discharge of treated landfill leachates reveals a fueled development of antibiotic resistance in receiving tidal river

Around 350 million tons of solid waste is disposed of in landfills every year globally, with millions of cubic meters of landfill leachates released into neighboring environment. However, to date, little is known about the variations of antimicrobial resistance (AMR) in on-site leachate treatment systems and its development in leachate-receiving water environment. Here, we quantified 7 subtypes of antibiotic resistance genes (ARGs), 3 types of culturable antibiotic resistant bacteria (ARB) and 6 subtypes of mobile genetic elements (MGEs) in the effluents from a combined leachate treatment process, including biological treatment (MBR), physical separation (UF), ultraviolet (UV) disinfection and advanced oxidation process (AOP). The contents of ARGs, ARB and MGEs were generally enriched by the MBR, but then decreased significantly along with the tertiary treatment process. However, in the effluent-receiving water samples, the abundance of dominant ARGs (i.e. ermB, sul1, bla_TEM) increased by 1.5 orders of magnitude within 96 h, alongside a general increase of MGEs (~10.0 log₁₀(copies/mL) and total ARB (~1100 CFU/mL). Structural correlation analyses reveal that target ARGs were closely associated with MGEs, particularly in effluent-receiving samples (Procrustes test; M² = 0.49, R = 0.71, P = 0.001); and occurrences of ARB were majorly affected by ARG's distribution and environmental conditions (e.g. nitrogen speciation) in effluent and recipient groups, respectively. This study indicates that current treatment technologies and operation protocols are not feasible in countering the development of AMR in effluent-receiving water environment, particularly in tidal rivers that are capable of retaining contaminants for a long residence time.

Behavior of tetracycline and sulfamethazine with corresponding resistance genes from swine wastewater in pilot-scale constructed wetlands

Four pilot-scale constructed wetlands (free water surface, SF; horizontal subsurface flow, HSF; vertical subsurface flows with different water level, VSF-L and VSF-H) were operated to assess their ability to remove sulfamethazine (SMZ) and tetracycline (TC) from wastewaters, and to investigate the abundance level of corresponding resistance genes (sulI, sulII, tetM, tetW and tetO) in the CWs. The results indicated that CWs could significantly reduce the concentration of antibiotics in wastewater, and the mass removal rate range of SMZ and TC were respectively 11%-95% and 85%-95% in the four systems on the basis of hydraulic equilibrium; further relatively high removal rate was observed in VSF with low water level. Seasonal condition had a significant effect on SMZ removal in the CWs (especially SMZ in SF), but TC removal in VSFs were not considered to have statistically significant differences in winter and summer. At the end period, the relative abundances of target genes in the CWs showed obvious increases compared to initial levels, ranging from 2.98 × 10(-5) to 1.27 × 10(-1) for sul genes and 4.68 × 10(-6) to 1.54 × 10(-1) for tet genes after treatment, and those abundances showed close relation to both characteristic of wastewater and configuration of CWs.