Disparate Antibiotic Resistance Gene Quantities Revealed across 4 Major Cities in California: A Survey in Drinking Water, Air, and Soil at 24 Public Parks

Transmission of human-pet antibiotic resistance via aerosols in pet hospitals of Changchun

In recent years, aerosols have been recognized as a prominent medium for the transmission of antibiotic-resistant bacteria and genes. Among these, particles with a particle size of 2 μm (PM2.5) can directly penetrate the alveoli. However, the presence of antibiotic-resistant genes in aerosols from pet hospitals and the potential risks posed by antibiotic-resistant bacteria in these aerosols to humans and animals need to be investigated. In this study, cefotaxime-resistant bacteria were collected from 5 representative pet hospitals in Changchun using a Six-Stage Andersen Cascade Impactor. The distribution of bacteria in each stage was analyzed, and bacteria from stage 5 and 6 were isolated and identified. Minimal inhibitory concentrations of isolates against 12 antimicrobials were determined using broth microdilution method. Quantitative Polymerase Chain Reaction was employed to detect resistance genes and mobile genetic elements that could facilitate resistance spread. The results indicated that ARBs were enriched in stage 5 (1.1-2.1 μm) and stage 3 (3.3-4.7 μm) of the sampler. A total of 159 isolates were collected from stage 5 and 6. Among these isolates, the genera Enterococcus spp. (51%), Staphylococcus spp. (19%), and Bacillus spp. (14%) were the most prevalent. The isolates exhibited the highest resistance to tetracycline and the lowest resistance to cefquinome. Furthermore, 56 (73%) isolates were multidrug-resistant. Quantitative PCR revealed the expression of 165 genes in these isolates, with mobile genetic elements showing the highest expression levels. In conclusion, PM2.5 from pet hospitals harbor a significant number of antibiotic-resistant bacteria and carry mobile genetic elements, posing a potential risk for alveolar infections and the dissemination of antibiotic resistance genes.

Review of emerging contaminants in green stormwater infrastructure: Antibiotic resistance genes, microplastics, tire wear particles, PFAS, and temperature

Green stormwater infrastructure is a growing management approach to capturing, infiltrating, and treating runoff at the source. However, there are several emerging contaminants for which green stormwater infrastructure has not been explicitly designed to mitigate and for which removal mechanisms are not yet well defined. This is an issue, as there is a growing understanding of the impact of emerging contaminants on human and environmental health. This paper presents a review of five emerging contaminants - antibiotic resistance genes, microplastics, tire wear particles, PFAS, and temperature - and seeks to improve our understanding of how green stormwater infrastructure is impacted by and can be designed to mitigate these emerging contaminants. To do so, we present a review of the source and transport of these contaminants to green stormwater infrastructure, specific treatment mechanisms within green infrastructure, and design considerations of green stormwater infrastructure that could lead to their removal. In addition, common removal mechanisms across these contaminants and limitations of green infrastructure for contaminant mitigation are discussed. Finally, we present future research directions that can help to advance the use of green infrastructure as a first line of defense for downstream water bodies against emerging contaminants of concern.

Spatiotemporal dynamics, traceability analysis, and exposure risks of antibiotic resistance genes in PM2.5 in Handan, China

Fine particulate matter (PM2.5) seriously affects environmental air quality and human health, and antibiotic resistance genes (ARGs) in PM2.5 posed a great challenge to clinical medicine. The year of 2013-2017 was an important 5-year period for the implementation of Air Pollution Prevention and Control Action Plan (APPCAP) in China. Here, we took Handan, a PM2.5 polluted city in northern China, as the research object and analyzed ARGs in PM2.5 in winter (January) from 2013 to 2017. The results showed that the abundance of ARGs was the highest in 2013 (3.7 × 10-2 copies/16S rRNA), and ARGs were positively correlated with air quality index (AQI) (r = 0.328, P < 0.05) and PM2.5 concentration (r = 0.377, P = 0.020 < 0.05) in the 5-year period. The ARGs carried by PM2.5 in four functional regions of sewage treatment plant, steel works, university, and park showed that sul1 and qepA had higher abundance in each functional region, and the total ARG abundance in sewage treatment plant (1.3 × 10-1 copies/16S rRNA) was the highest, while lowest in park (2.0 × 10-3 copies/16S rRNA). Potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) model were used to trace the pollutants at the sampling points, which indicated that the surrounding cities contributed more than quarter to the sampling points. Therefore, regional transportation reduces the spatial distribution difference of ARGs in PM2.5. The exposure dose of ARGs in different functional regions illustrated that the total inhaled dose of ARGs in sewage treatment plant (1.7 × 105 copies/d) was the highest, while lowest in park (3.2 × 104 copies/d). This study is of great significance for assessing the distribution and sources of ARGs under the clean air initiative in China.

Study on microbes and antibiotic resistance genes in karst primitive mountain marshes - A case study of Niangniang Mountain in Guizhou, China

Previous research on antibiotic resistance genes and microorganisms centered on those in urban sewage treatment plants, breeding farms, hospitals and others with serious antibiotic pollution. However, at present, there are evident proofs that antibiotic resistance genes (ARGs) indeed exist in a primitive environment hardly without any human's footprints. Accordingly, an original karst mountain swamp ecosystem in Niangniang Mountain, Guizhou, China, including herbaceous swamp, shrub swamp, sphagnum bog and forest swamp, was selected to analyze the physical and chemical parameters of sediments. Moreover, microbial compositions, functions, as well as their connections with ARGs were assayed and analyzed using metagenomic technology. The results showed that there was no significant difference in the dominant microorganisms and ARGs in the four marshes, in which the dominant bacteria phyla were Proteobacteria (37.82 %), Acidobacteriota (22.17 %) and Actinobacteriota (20.64 %); the dominant archaea Euryarchaeota. (1.00 %); and the dominant eukaryotes Ascomycota (0.07 %), with metabolism as their major functions. Based on the ARDB database, the number of ARGs annotated reached 209 including 30 subtypes, and the dominant ARGs were all Bacitracin resistance genes (bacA, 84.77 %). In terms of the diversity of microorganisms and ARGs, the herbaceous swamp ranked the top, and the shrub swamp were at the bottom. Correlation analysis between microorganisms and resistance genes showed that, apart from aac2ic, macB, smeE, tetQ, and tetL, other ARGs were positively correlated with microorganisms. Among them, baca coexisted with microorganisms. Pearson correlation analysis results showed that contrary to ARGs, microorganisms were more affected by environmental factors.

Co-driving factors of tidal effect on the abundance and distribution of antibiotic resistance genes in the Yongjiang Estuary, China

The unreasonable use of antibiotics and the transmission of antibiotic resistance genes (ARGs) induced by antibiotics have led to a large number of ARGs entered the water environment, which seriously threatened human health and environmental safety. The estuarine aquatic environment connects with inland rivers and sea and is frequently influenced by human activities. This study aims to reveal the occurrences and abundances of ARGs and bacterial community composition by high-throughput quantitative PCR including 296 primers and high-throughput sequencing in the tide rising and ebbing of surface water in the Yongjiang Estuary, China. The results showed that there were a large number of ARGs and mobile genetic elements (MGEs) detected in the rising tide and ebb tide water bodies. The numbers of detected ARGs in each sample at rising and ebb tide ranged from 16 to 77 and 61 to 88, respectively, and the absolute abundance ranges were 1.69 × 10⁴-1.69 × 10⁹ copies/L and 3.18 × 10³-2.57 × 10⁹ copies/L, respectively. Obvious tidal distribution characteristics of ARGs were showed. Most of ARGs conferred resistance to multidrug, aminoglycosides and sulfanilamides. Proteobacteria, Actinobacteria and Bacteroidetes were the dominantly bacterial phylum in the Yongjiang Estuary. Network analysis results indicated that multi-genera were identified as possible ARGs hosts, and they carried more than two types of ARGs genes. Partial least squares path modeling further revealed that MGEs and bacterial community composition were the most important driving factors. The results of the study can provide the corresponding scientific basis for the diffusion and control of ARGs in estuaries.

Effects of antibiotics consumption on the behavior of airborne antibiotic resistance genes in chicken farms

The antibiotics and antibiotic resistance genes (ARGs) have caused pollution of livestock farm environments. There are limited investigations about airborne ARGs and what role the antibiotics play remains largely unclear. The dynamics of various antibiotics were compared between feces samples from chicken fed a diet with and without antibiotics. In contrast to the farm with no antibiotics drugs, the hazard quotients (HQs) of OTC (24.8-205.4) and CTC (18.0-317.0) are particularly high in the farm with in-feed antibiotics drugs. The high ecological risks of antibiotics in chicken feces with in-feed antibiotic drugs were 100 % as determined. We quantified mobile genetic elements (MGEs) and ARGs and investigated bacterial communities in feces and air samples. The concentration of airborne ARG/MGE subtypes with in-feed antibiotic drugs is about two orders of magnitude higher than those without drugs. This study reveals that the indoor air of chicken farms is a reservoir of ARGs in the environment. Continuous feeding of antibiotics can change the intestinal microbial community structure of the chicken. The possibility of horizontal gene transfer of ARGs in air and feces samples might be increased by in-feed antibiotic drugs. The enrichment of ARGs in the chicken farm can be reduced by minimizing antibiotic use.

Urbanization drives the succession of antibiotic resistome and microbiome in a river watershed

Urbanization is a process of ecosystem evolution mediated by human activities. One of the main consequences is the alteration of antibiotic resistome and microbiome in aquatic environment, which may transfer from water to sediments and exert a long-term health concern to aquatic animals and even humans. However, the role of urbanization in shaping resistome and microbiome in water and sediments is largely unknown. Here, a typical watershed with a significant gradient of urbanization was selected, and the resistome and microbiome in both water and sediments were profiled. In water, the relative abundance of ARGs and bacterial diversity increased gradually along the urbanization, but were relatively stable in sediments. The abundance of potential multidrug-resistant bacteria in peri-urban and urban water were significantly higher than rural water, while in sediments, unique potential multidrug-resistant bacteria were detected at different urbanization levels. Population size was identified as the key factor shaping the ARGs profiles. Finally, environmental risk assessment based on the projection pursuit regression model suggested that the water in urban region had higher potential environmental risk of antibiotic resistance, in contrary to the sediments in rural and peri-urban regions. Our findings revealed distinct responses of water and sediment to urbanization in terms of antibiotic resistome and microbiome. This work provides important guide for hierarchically controlling ARGs dissemination in watershed.

Critical review of antibiotic resistance genes in the atmosphere

We conducted a critical review to establish what is known about the sources, characteristics, and dissemination of ARGs in the atmosphere. We identified 52 papers that reported direct measurements of bacterial ARGs in air samples and met other inclusion criteria. The settings of the studies fell into the following categories: urban, rural, hospital, industrial, wastewater treatment plants (WWTPs), composting and landfill sites, and indoor environments. Certain genes were commonly studied and generally abundant: sul1, intI1, β-lactam ARGs, and tetracycline ARGs. Abundances of total ARGs varied by season and setting, with air in urban areas having higher ARG abundance than rural areas during the summer and vice versa during the winter. There was greater consistency in the types and abundances of ARGs throughout the seasons in urban areas. Human activity within indoor environments was also linked to increased ARG content (abundance, diversity, and concentration) in the air. Several studies found that human exposure to ARGs through inhalation was comparable to exposure through drinking water or ingesting soil. Detection of ARGs in air is a developing field, and differences in sampling and analysis methods reflect the many possible approaches to studying ARGs in air and make direct comparisons between studies difficult. Methodologies need to be standardized to facilitate identification of the dominant ARGs in the air, determine their major sources, and quantify the role of atmospheric transport in dissemination of ARGs in the environment. With such knowledge we can develop better policies and guidelines to limit the spread of antimicrobial resistance.

Tracking antibiotic resistance through the environment near a biosolid spreading ground: Resistome changes, distribution, and metal(loid) co-selection

The application of urban wastewater treatment plants (WWTPs) products to agricultural lands has contributed to the rising level of antibiotic resistance and drawn a critical public health concern. It has not been thoroughly investigated at which spatial scales a biosolid applied area as a potentially predominant source affects surrounding soil resistomes. This study investigated distribution and impact of WWTP biosolids treated with anaerobic digestion on an agricultural area. Heterotrophic plate counts (HPCs) and quantitative polymerase chain reaction (qPCR) were performed for detection of selected antibiotic-resistant bacteria (ARB), selected antibiotic resistance genes (ARGs), intI1 genes, and 16S rRNA genes. Biosolid samples contained significantly higher levels of selected ARGs than the raw agricultural soils (p < 0.05). The average relative abundances of intI1, sul1, bla_SHV, and ermB genes were significantly higher in biosolid-amended soils than nearby agricultural soils (p < 0.05). Spatial interpolation analysis of relative gene abundances of intI1, sul1, sul2, and tetW across the studied area further indicated directional trends towards the northwest and southeast directions, highlighting possible airborne spread. Concentrations of Co, Cu, Ni, and Fe were found to be significantly and positively correlated with relative abundances of intI1, sul1, and tetW genes (p < 0.05). The resistance ratios of culturable antibiotic-resistant bacteria in agricultural soils with biosolid amendments were generally identical to those without biosolid amendments. This study will advance the understanding of the antibiotic resistome in agricultural soils impacted by long-term waste reuse and inform the evaluation strategies for future biosolids application and management.

Influence of soil characteristics and metal(loid)s on antibiotic resistance genes in green stormwater infrastructure in Southern California

The synergetic effects of metal(loid)s and soil characteristics on bacterial antibiotic resistance genes (ARGs) in green stormwater infrastructure (GSI) has been relatively understudied. Surface soil samples from six GSIs in Southern California over three time periods were assessed for selected ARGs, class 1 integron-integrase genes (intI1), 16S rRNA genes, and bioavailable and total concentrations of nine metal(loid)s, to investigate the relationships among ARGs, soil characteristics, and co-occurring metal(loid)s. Significant correlations existed among relative gene abundances (sul1, sul2, tetW, and intI1), total metal(loid)s (arsenic, copper, lead, vanadium, and zinc), and bioavailable metal(loid) (arsenic) (r = 0.29-0.61, p_adj < 0.05). Additionally, soil texture, organic matter, and nutrients within GSI appeared to be significantly correlated with relative gene abundances of sul1, sul2, and tetW (r = -0.57 to 0.59, p_adj < 0.05). Multiple regression models significantly improved the estimation of ARGs in GSI when considering multiple effects of soil characteristics and metal(loid)s (r = 0.74, p_adj < 0.001) compared to correlation results. Total arsenic was a significant (positive) correlate in all the regression models of relative gene abundances. This work provides new insights into co-dependencies between GSI ARGs and co-occurring metal(loid)s, indicating the need for risk assessment of metal(loid)-influenced ARG proliferation.

A review of the emergence of antibiotic resistance in bioaerosols and its monitoring methods

Despite significant public health concerns regarding infectious diseases in air environments, potentially harmful microbiological indicators, such as antibiotic resistance genes (ARGs) in bioaerosols, have not received significant attention. Traditionally, bioaerosol studies have focused on the characterization of microbial communities; however, a more serious problem has recently arisen due to the presence of ARGs in bioaerosols, leading to an increased prevalence of horizontal gene transfer (HGT). This constitutes a process by which bacteria transfer genes to other environmental media and consequently cause infectious disease. Antibiotic resistance in water and soil environments has been extensively investigated in the past few years by applying advanced molecular and biotechnological methods. However, ARGs in bioaerosols have not received much attention. In addition, ARG and HGT profiling in air environments is greatly limited in field studies due to the absence of suitable methodological approaches. Therefore, this study comprehensively describes recent findings from published studies and some of the appropriate molecular and biotechnological methods for monitoring antibiotic resistance in bioaerosols. In addition, this review discusses the main knowledge gaps regarding current methodological issues and future research directions.

Detection of antimicrobial resistance genes in urban air

To understand antibiotic resistance in pathogenic bacteria, we need to monitor environmental microbes as reservoirs of antimicrobial resistance genes (ARGs). These bacteria are present in the air and can be investigated with the whole metagenome shotgun sequencing approach. This study aimed to investigate the feasibility of a method for metagenomic analysis of microbial composition and ARGs in the outdoor air. Air samples were collected with a Harvard impactor in the PM10 range at 50 m from a hospital in Budapest. From the DNA yielded from samples of PM10 fraction single-end reads were generated with an Ion Torrent sequencer. During the metagenomic analysis, reads were classified taxonomically. The core bacteriome was defined. Reads were assembled to contigs and the ARG content was analyzed. The dominant genera in the core bacteriome were Bacillus, Acinetobacter, Leclercia and Paenibacillus. Among the identified ARGs best hits were vanRA, Bla1, mphL, Escherichia coli EF-Tu mutants conferring resistance to pulvomycin; BcI, FosB, and mphM. Despite the low DNA content of the samples of PM10 fraction, the number of detected airborne ARGs was surprisingly high.

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.

Commercially available garden products as important sources of antibiotic resistance genes-a survey

The dissemination of antibiotic resistance genes (ARGs) in the environment contributes to the global rise in antibiotic resistant infections. Therefore, it is of importance to further research the exposure pathways of these emerging contaminants to humans. This study explores commercially available garden products containing animal manure as a source of ARGs in a survey of 34 garden products, 3 recently landscaped soils, and 5 native soils. DNA was extracted from these soils and quantified for 5 ARGs, intI1, and 16S rRNA. This study found that both absolute and relative gene abundances in garden products ranged from approximately two to greater than four orders of magnitude higher than those observed in native soils. Garden products with Organic Materials Review Institute (OMRI) certification did not have significantly different ARG abundances. Results here indicate that garden products are important sources of ARGs to gardens, lawns, and parks.

Removal of antibiotic-resistant genes during drinking water treatment: A review

Once contaminate the drinking water source, antibiotic resistance genes (ARGs) will propagate in drinking water systems and pose a serious risk to human health. Therefore, the drinking water treatment processes (DWTPs) are critical to manage the risks posed by ARGs. This study summarizes the prevalence of ARGs in raw water sources and treated drinking water worldwide. In addition, the removal efficiency of ARGs and related mechanisms by different DWTPs are reviewed. Abiotic and biotic factors that affect ARGs elimination are also discussed. The data on presence of ARGs in drinking water help come to the conclusion that ARGs pollution is prevalent and deserves a high priority. Generally, DWTPs indeed achieve ARGs removal, but some biological treatment processes such as biological activated carbon filtration may promote antibiotic resistance due to the enrichment of ARGs in the biofilm. The finding that disinfection and membrane filtration are superior to other DWTPs adds weight to the advice that DWTPs should adopt multiple disinfection barriers, as well as keep sufficient chlorine residuals to inhibit re-growth of ARGs during subsequent distribution. Mechanistically, DWTPs obtain direct and inderect ARGs reduction through DNA damage and interception of host bacterias of ARGs. Thus, escaping of intracellular ARGs to extracellular environment, induced by DWTPs, should be advoided. This review provides the theoretical support for developping efficient reduction technologies of ARGs. Future study should focus on ARGs controlling in terms of transmissibility or persistence through DWTPs due to their biological related nature and ubiquitous presence of biofilm in the treatment unit.

Open Waste Canals as Potential Sources of Antimicrobial Resistance Genes in Aerosols in Urban Kanpur, India

Understanding the movement of antimicrobial resistance genes (ARGs) in the environment is critical to managing their spread. To assess potential ARG transport through the air via urban bioaerosols in cities with poor sanitation, we quantified ARGs and a mobile integron (MI) in ambient air over periods spanning rainy and dry seasons in Kanpur, India (n = 53), where open wastewater canals (OWCs) are prevalent. Gene targets represented major antibiotic groups-tetracyclines (tetA), fluoroquinolines (qnrB), and beta-lactams (blaTEM)-and a class 1 mobile integron (intI1). Over half of air samples located near, and up to 1 km from OWCs with fecal contamination (n = 45) in Kanpur had detectable targets above the experimentally determined limits of detection (LOD): most commonly intI1 and tetA (56% and 51% of samples, respectively), followed by blaTEM (8.9%) and qnrB (0%). ARG and MI densities in these positive air samples ranged from 6.9 × 101 to 5.2 × 103 gene copies/m3 air. Most (7/8) control samples collected 1 km away from OWCs were negative for any targets. In comparing experimental samples with control samples, we found that intI1 and tetA densities in air are significantly higher (P = 0.04 and P = 0.01, respectively, alpha = 0.05) near laboratory-confirmed fecal contaminated waters than at the control site. These data suggest increased densities of ARGs and MIs in bioaerosols in urban environments with inadequate sanitation. In such settings, aerosols may play a role in the spread of AR.

Antimicrobial resistance genes are enriched in aerosols near impacted urban surface waters in La Paz, Bolivia

Antibiotic resistance poses a major global health threat. Understanding emergence and dissemination of antibiotic resistance in environmental media is critical to the design of control strategies. Because antibiotic resistance genes (ARGs) may be aerosolized from contaminated point sources and disseminated more widely in localized environments, we assessed ARGs in aerosols in urban La Paz, Bolivia, where wastewater flows in engineered surface water channels through the densely populated urban core. We quantified key ARGs and a mobile integron (MI) via ddPCR and E. coli spp. as a fecal indicator by culture over two years during both the rainy and dry seasons in sites near wastewater flows. ARG targets represented major antibiotic groups-tetracyclines (tetA), fluoroquinolines (qnrB), and beta-lactams (blaTEM)-and an MI (intI1) represented the potential for mobility of genetic material. Most air samples (82%) had detectable targets above the experimentally determined LOD: most commonly blaTEM and intI1 (68% and 47% respectively) followed by tetA and qnrB (17% and 11% respectively). ARG and MI densities in positive air samples ranged from 1.3 × 101 to 6.6 × 104 gene copies/m3 air. Additionally, we detected culturable E. coli in the air (52% of samples <1 km from impacted surface waters) with an average density of 11 CFU/m3 in positive samples. We observed decreasing density of blaTEM with increasing distance up to 150 m from impacted surface waters. To our knowledge this is the first study conducting absolute quantification and a spatial analysis of ARGs and MIs in ambient urban air of a city with contaminated surface waters. Environments in close proximity to urban wastewater flows in this setting may experience locally elevated concentrations of ARGs, a possible concern for the emergence and dissemination of antimicrobial resistance in cities with poor sanitation.

Characteristics of and variation in airborne ARGs among urban hospitals and adjacent urban and suburban communities: A metagenomic approach

Environmental antibiotic resistance genes (ARGs) have received much attention, while the characteristics of ARGs carried by particulate matter (PM) as a function of urban functional region are almost unknown. In this study, ARGs carried by PM_2.5 and PM₁₀ in an urban hospital, a nearby urban community and the nearest suburban community were detected using metagenomics. In total, 643 ARG subtypes belonging to 22 different ARG types were identified. The chloramphenicol exporter gene, sul1, bacA, and lnuA were the most abundant ARG subtypes in all air samples. The hospital exhibited higher ARG abundance and richness than the nearby communities. ARG profiles depended on functional region: hospital and suburban samples clustered separately, and samples from the nearby urban community interspersed among them. The representation of multidrug and quinolone resistance genes decayed with distance from the hospital to the urban community to the suburban community, indicating that hospital PM may be a hotspot for ARGs encoding proteins conferring multidrug and quinolone resistance. Airborne ARGs carried by PM in the hospital environment were more closely associated with clinically important pathogens than were those in nearby communities. In particular, carbapenemase genes, including bla_NDM,bla_KPC,bla_IMP,bla_VIM,and bla_OXA-48, were discovered in hospital PM. In the suburban community, crAssphage, a human host-specific bacteriophage, was applied to predict ARG abundance and found to be enriched due to anthropogenic pollution but showed no clear evidence for ARG selection. In the hospital and the nearby urban community, the drivers of ARGs were complex. Our results highlighted that PM ARGs were closely related to human activities and revealed a potential hotspot, which could provide new evidence for further research and consequently mitigate the formation of airborne ARGs and transfer risks.

Occurrence, distribution, and source track of antibiotics and antibiotic resistance genes in the main rivers of Chongqing city, Southwest China

In this study, the occurrence of 14 antibiotics, four corresponding antibiotic resistance genes (ARGs) and two microbial source tracker (MST) indicators were analyzed in two rivers of Chongqing city, southwest China. The results showed that 13 antibiotics were detected in all 12 sites and their detection frequencies were much higher in September, but concentrations were lower than that in March. Of them, erythromycin (ETM) and ofloxacin (OFL) were the predominant antibiotics in both seasons. The remarkably higher concentration of antibiotics in sediments of these rivers than those in other rivers were found. Environmental risk assessment found that four antibiotics posed high risk toward some sensitive algae. For ARGs, their relative abundances were higher in waters than those in sediments, higher in March than in September. Correlation analysis showed that antibiotics were not the exclusive selective pressure of ARGs; many environmental factors like dry matter contents on a mass basis, organic matter, total organic carbon, dissolved organic carbon, temperature, oxidation reduction potential and nitrite could affect the occurrence of ARGs. MST indicators analysis demonstrated that this river basin was largely polluted by human and pig feces, and human feces might be one main source of the four ARGs and five antibiotics.

Zoonosis: An Emerging Link to Antibiotic Resistance Under "One Health Approach"

Current scenario in communicable diseases has generated new era that identifies the "One health" approach to understand the sharing and management of etiological agents with its impact on ecosystem. Under this context the relevance of zoonotic diseases generates major concern. The indiscriminate and higher use of antibiotics in animal husbandry creates substantial pressure on the gut microbiome for development of resistance due to shorter generation time and high density. Thus, gut works as a bioreactor for the breeding of ARBs in this scenario and are continuously released in different niches. These ARBs transfer resistance genes among native flora through horizontal gene transfer events, vectors and quorum sensing. About 60% of infectious diseases in human are caused by zoonotic pathogens have potential to carry ARGs which could be transmitted to humans. The well documented zoonotic diseases are anthrax cause by Bacillus anthracis, bovine tuberculosis by Mycobacterium tuberculosis, brucellosis by Brucella abortus, and hemorrhagic colitis by Escherichia coli. Similarly, most of the antibiotics are not completely metabolized and released in unmetabolized forms which enters the food chain and affect various ecological niches through bioaccumulation. The persistence period of antibiotics ranges from < 1 to 3466 days in environment. The consequences of misusing the antibiotic in livestock and their fate in various ecological niches have been discussed in this review. Further the light sheds on antibiotics persistence and it biodegradation through different abiotic and biotic approaches in environment. The knowledge on personnel hygiene and strong surveillance system for zoonotic disease including ARBs transmission, prevention and control measures should be established to regulate the spread of AMR in the environment and subsequently to the human being through a food web.

Distribution of antibiotic resistance genes and bacteria from six atmospheric environments: Exposure risk to human

Antibiotic resistance genes (ARGs), as an emerging environmental pollutant, have received widespread attention. There are many studies on ARGs in water and soil. However, there are few studies on airborne ARGs. We used qPCR to detect 19 ARG subtypes in six atmospheric environments. Among the different atmospheric environments including wastewater treatment plant (fine screens and sludge thickener), bathroom, laboratory, hospital and outdoor, the highest total concentration of ARGs is detected in the haze outdoor (9 × 10⁵ copies/m³), while the lowest is in the bathroom atmosphere (4.2 × 10⁴ copies/m³). Furthermore, β-lactam ARGs are found to be the dominant ARGs in these 6 atmospheric environments. Due to the large number and widespread use of antibiotics, the airborne ARGs in hospital have the highest diversity and equitability. The β-lactam ARGs are significantly positively correlated with sulfonamides ARGs, indicating the mechanism of co-resistance since these two ARGs may be on the same genetic elements and thus simultaneously exhibit both resistances. The network analysis provides potential host information between the airborne ARGs and the coexisted microbial taxa. Sphingomonas and Bradyhizoblum strains presumably host for tetracycline and β-lactam ARGs, respectively. The ADD_outdoor of bla_TEM-1 was 7.8 × 10⁵ copies/d/kg, more than the ADD (7.6 × 10³ copies/d/kg) of bla_TEM-1 by drinking water. We can't ignore ARGs in the atmospheric environments.

Antibiotic resistance in urban green spaces mirrors the pattern of industrial distribution

Urban green spaces are closely related to the activities and health of urban residents. Turf grass and soil are two major interfaces between the environmental and human microbiome, which represent potential pathways for the spread of antibiotic resistance genes (ARGs) from environmental to human microbiome through skin-surface contact. However, the information regarding the prevalence of ARGs in urban green spaces and drivers in shaping their distribution patterns remain unclear. Here, we profiled a wide spectrum of ARGs in grass phyllosphere and soils from 40 urban parks across Greater Melbourne, Australia, using high throughput quantitative PCR. A total of 217 and 218 unique ARGs and MGEs were detected in grass phyllosphere and soils, respectively, conferring resistance to almost all major classes of antibiotics commonly used in human and animals. The plant microbiome contained a core resistome, which occupied >84% of the total abundance of ARGs. In contrast, no core resistome was identified in the soil microbiome. The difference between plant and soil resistome composition was attributed to the difference in bacterial community structure and intensity of environmental and anthropogenic influence. Most importantly, the abundance of ARGs in urban green spaces was significantly positively related to industrial factors including total number of business, number of manufacturing, and number of electricity, gas, water and waste services in the region. Structural equation models further revealed that industrial distribution was a major factor shaping the ARG profiles in urban green spaces after accounting for multiple drivers. These findings have important implications for mitigation of the potential risks posed by ARGs to urban residents.

Bacteria and Antibiotic Resistance Genes (ARGs) in PM2.5 from China: Implications for Human Exposure

Airborne transmission is one of the environmental dissemination pathways of antibiotic resistance genes (ARGs), and has critical implications for human exposure through inhalation. In this study, we focused on three regions of China to reveal some unique spatiotemporal features of airborne bacteria and ARGs in fine aerosols (PM_2.5): (1) greater seasonal variations in the abundance of bacteria and ARGs in temperate urban Beijing than in the subtropical urban areas of the Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions, with regional disparities in bacterial communities; (2) geographical fingerprints of ARG profiles independent of seasonal cycles and land-use gradients within each region; (3) region-independent associations between the targeted ARGs and limited bacterial genera; (4) common correlations between ARGs and mobile genetic elements (MGEs) across regions; and (5) PM_2.5 at the higher end of ARG enrichment across various environmental and human media. The spatiotemporally differentiated bacterial communities and ARG abundances, and the compositions, mobility, and potential hosts of ARGs in the atmosphere have strong implications for human inhalational exposure over spatiotemporal scales. By comparing other contributing pathways for the intake of ARGs (e.g., drinking water and food ingestion) in China and the U.S.A., we identified the region-specific importance of inhalation in China as well as country-specific exposure scenarios. Our study thus highlights the significance of inhalation as an integral part of the aggregate exposure pathways of environmentally disseminated ARGs, which, in turn, may help in the formulation of adaptive strategies to mitigate the exposure risks in China and beyond.

Global Survey of Antibiotic Resistance Genes in Air

Despite its emerging significant public health concern, the presence of antibiotic resistance genes (ARGs) in urban air has not received significant attention. Here, we profiled relative abundances (as a fraction, normalized by 16S rRNA gene) of 30 ARG subtypes resistant to seven common classes of antibiotics, which are quinolones, β-lactams, macrolides, tetracyclines, sulfonamides, aminoglycosides, and vancomycins, in ambient total particulate matter (PM) using a novel protocol across 19 world cities. In addition, their longitudinal changes in PM_2.5 samples in Xi'an, China as an example were also studied. Geographically, the ARGs were detected to vary by nearly 100-fold in their abundances, for example, from 0.07 (Bandung, Indonesia) to 5.6 (San Francisco, USA). The β-lactam resistance gene blaTEM was found to be most abundant, seconded by quinolone resistance gene qepA; and their corresponding relative abundances have increased by 178% and 26%, respectively, from 2004 to 2014 in Xi'an. Independent of cities, gene network analysis indicates that airborne ARGs were differentially contributed by bacterial taxa. Results here reveal that urban air is being polluted by ARGs, and different cities are challenged with varying health risks associated with airborne ARG exposure. This work highlights the threat of urban airborne transmission of ARGs and the need of redefining our current air quality standards in terms with public health.