Global Survey of Antibiotic Resistance Genes in Air

Antibiotics and Pesticides Enhancing the Transfer of Resistomes among Soil-Bayberry-Fruit Fly Food Chain in the Orchard Ecosystem

While substantial amounts of antibiotics and pesticides are applied to maintain orchard yields, their influence on the dissemination and risk of antibiotic resisitome in the orchard food chain remains poorly understood. In this study, we characterized the bacterial and fungal communities and differentiated both antibiotic resistance genes (ARGs) and virulence factor genes (VFGs) in the soil, Chinese bayberry (matured and fallen), and fruit fly gut, collected from five geographic locations. Our results showed that fruit fly guts and soils exhibit a higher abundance of ARGs and VFGs compared with bayberry fruits. We identified 112 shared ARGs and 75 shared VFGs, with aminoglycoside and adherence factor genes being among the most abundant. The co-occurrence network revealed some shared microbes, such as Bacillus and Candida, as potential hosts of ARGs, highlighting the vector risks for both above- and below-ground parts of the orchard food chain. Notably, the elevated levels of antibiotics and pesticide residues in orchard soils increase ARGs, mobile genetic elements (MGEs), and VFGs in the soil-bayberry-fruit fly food chain. Our study highlighted that agricultural management, including the overuse of antibiotics and pesticides, could be the key factor in accumulating resistomes in the orchard food chain.

The climate change-pollution-aerobiome nexus: A 'systems thinking' mini-review

The interrelationship between climate change, pollution and the aerobiome (the microbiome of the air) is a complex ecological dynamic with profound implications for human and ecosystem health. This mini-review explores the multifaceted relationships among these factors. By synthesising existing research and integrating interdisciplinary perspectives, we examine the mechanisms driving interactions within the climate change-pollution-aerobiome nexus. We also explore synergistic and cascading effects and potential impacts on human health (including both communicable and non-communicable diseases) and that of wider ecosystems. Based on our mini-review results, climate change influences air pollution and, independently, air pollution affects the composition, diversity and activity of the aerobiome. However, we apply a 'systems thinking' approach and create a set of systems diagrams to show that climate change likely influences the aerobiome (including bacteria and fungi) via climate change-pollution interactions in complex ways. Due to the inherent complexity of these systems, we emphasise the importance of holistic and/or interdisciplinary approaches and collaborative efforts in understanding this nexus to safeguard planetary health in an era of rapid environmental change.

Airborne antibiotic resistome from sludge dewatering systems: Mobility, pathogen accessibility, cross-media migration propensity, impacting factors, and risks

Bioaerosol contamination was considered as a potential health threat in sludge dewatering systems (SDSs), while emission and risk of airborne antibiotic resistome remain largely unclear. Herein, seasonal investigations of fine particulate matter (PM2.5) were conducted using metagenomics-based methods within and around different SDSs, together with an analysis of sewage sludge. Featured with evident seasonality, antibiotic resistance genes (ARGs) in SDS-PM2.5 also possessed greater accumulation, transfer, and pathogen accessibility than those in ambient air PM2.5. Mobile ARGs in SDS-PM2.5 mainly encoded resistance to tetracycline, and most were flanked by integrase. Some pathogenic antibiotic resistant bacteria (PARB), including Enterobacter asburiae, Escherichia coli, Enterococcus faecium, and Staphylococcus aureus, also carried mobile genetic elements in SDS-PM2.5. Dewatering behavior actuated > 50.56% of ARG subtypes and > 42.86% of PARB in sewage sludge to aerosolize into air. Relative humidity, temperature, and PM2.5 concentration collectively drove the evolution of bacterial community and indirectly promoted the antibiotic resistance of SDS-PM2.5. SDS-PM2.5 posed more serious resistome risks than sewage sludge and ambient air PM2.5, and the highest levels were discovered in winter. These findings underline the role of dewatering behavior in facilitating resistome's aerosolization, and the need to mitigate this potential air pollution.

Context-Seq: CRISPR-Cas9 Targeted Nanopore Sequencing for Transmission Dynamics of Antimicrobial Resistance

Antimicrobial resistance (AMR) aligns with a One Health framework in that resistant bacteria and antibiotic resistance genes (ARGs) can be transmitted between humans, animals, and the environment. However, there is a critical need to more precisely understand how and to what extent AMR is exchanged between animals and humans. Metagenomic sequencing has low detection for rare targets such as ARGs, while whole genome sequencing of isolates is burdensome and misses exchange between uncultured bacterial species. We developed a novel, targeted sequencing assay using CRISPR-Cas9 to selectively sequence ARGs and their genomic context with long-read sequencing. Using this method, termed Context-Seq, we investigated overlapping AMR elements containing the ARGs bla CTX-M and bla TEM between adults, children, poultry, and dogs in animal-owning households in Nairobi, Kenya. We identified 22 genetically distinct clusters (> 80%ID over ≥ 3000 bp) containing bla TEM and one cluster containing bla CTX-M that were shared within and between households. Half of the clusters were shared between humans and animals, while the other half were shared only between animals (poultry-poultry, dog-dog, and dog-poultry). We identified potentially pathogenic hosts of ARGs including Escherichia coli, Klebsiella pneumonia, and Haemophilus influenzae across sample types. Context-Seq complements conventional methods to obtain an additional view of bacterial and mammalian hosts in the proliferation of AMR.

Occurrence and human exposure risk of antibiotic resistance genes in tillage soils of dryland regions: A case study of northern Ningxia Plain, China

Agricultural soils are important source and sink of antibiotic resistance genes (ARGs). However, little is known about the fate of ARGs in dryland soils, while its human exposure risks were seriously overlooked. Taking the northern Ningxia Plain as a case, this study explored the occurrence of ARGs and its relationship with mobile genetic elements (MGEs), pathogens, and environmental factors. Furthermore, the concentrations of airborne ARGs by soil wind erosion and the human exposure doses of soil ARGs were evaluated. The results showed the abundances of different regions ranged from 4.0 × 105 to 1.6 × 106 copies/g. Soil ARGs are driven by MGEs, but multiply impacted by soil properties, nutrition, and bacterial community. Vibrio metschnikovii, Acinetobacter schindleri, and Serratia marcescens are potential pathogenic hosts for ARGs. Further exploration revealed the concentration of ARGs loaded in dust by soil wind erosion reached more than 105 copies/m3, which were even higher than those found in sewage treatment plants and hospitals. Skin contact is the primary route of ARGs exposure, with a maximum dose of 24071.33 copies/kg/d, which is largely attributed to ARGs loaded in dust. This study bridged the gap on ARGs in dryland soils, and provided reference for human exposure risk assessment of soil ARGs.

Antibiotic resistance of heterotrophic bacteria from the sediments of adjoining high Arctic fjords, Svalbard

Antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) are now considered major global threats. The Kongsfjorden and Krossfjorden are the interlinked fjords in the Arctic that are currently experiencing the effects of climate change and receiving input of pollutants from distant and regional sources. The present study focused on understanding the prevalence of antibiotic resistance of retrievable heterotrophic bacteria from the sediments of adjacent Arctic fjords Kongsfjorden and Krossfjorden. A total of 237 bacterial isolates were tested against 16 different antibiotics. The higher resistance observed towards Extended Spectrum β-lactam antibiotic (ESBL) includes ceftazidime (45.56%) followed by trimethoprim (27%) and sulphamethizole (24.05%). The extent of resistance was meagre against tetracycline (2.53%) and gentamycin (2.95%). The 16S rRNA sequencing analysis identified that Proteobacteria (56%) were the dominant antibiotic resistant phyla, followed by Firmicutes (35%), Actinobacteria (8%) and Bacteroidetes. The dominant resistant bacterial isolates are Bacillus cereus (10%), followed by Alcaligenes faecalis (6.47%), Cytobacillus firmus (5.75%) Salinibacterium sp. (5%) and Marinobacter antarcticus (5%). Our study reveals the prevalence of antibiotic resistance showed significant differences in both the inner and outer fjords of Kongsfjorden and Krossfjorden (p < 0.05). This may be the input of antibiotic resistance bacteria released into the fjords from the preserved permafrost due to the melting of glaciers, horizontal gene transfer, and human influence in the Arctic region act as a selection pressure for the development and dissemination of more antibiotic resistant bacteria in Arctic fjords.

Transfer of antibiotic resistance genes from soil to rice in paddy field

The global spread and distribution of antibiotic resistance genes (ARGs) has received much attention whereas knowledge about the transmission of ARGs from one matrix to another is still insufficient. In this study, the paddy fields fertilized with chemical fertilizer, swine compost, and no fertilizer were investigated to assess the transfer of ARGs from soil to rice. Soil and plant samples were collected at day 0, 7, 30 and 79 representing various stages of paddy growth. High throughput qPCR was applied to quantify ARGs using a set of 144 primers. Gene copy number of ARGs measured in soil initially decreased and then increased in soil with no fertilizer and chemical fertilizer, indicating that crop planting and flooding conditions did influence the ARGs profiles in soil. Application of swine compost significantly enhanced the relative abundance and gene copy number of ARGs in paddy soil. Rice seedlings contained substantial amount of ARGs and their relative abundance continually decreased after transplant. Compared with initial stage, detection frequencies of ARGs increased in soil without swine compost at harvest time (day 79), indicating the transmission of ARGs from irrigation water to soil. Detection frequencies of ARGs increased in soil and rice root with swine compost at harvest time, indicating the transfer of ARGs from swine compost to soil and rice root. There was no significant difference in abundance and diversity of ARGs in rice grains with these three different fertilizations. The source of the ARGs in rice grain still needs further exploration.

The abundance and pathogenicity of microbes in automobile air conditioning filters across the typical cities of China and Europe

Bioaerosols are widely distributed in urban air and can be transmitted across the atmosphere, biosphere, and anthroposphere, resulting in infectious diseases. Automobile air conditioning (AAC) filters can trap airborne microbes. In this study, AAC filters were used to investigate the abundance and pathogenicity of airborne microorganisms in typical Chinese and European cities. Culturable bacteria and fungi concentrations were determined using microbial culturing. High-throughput sequencing was employed to analyze microbial community structures. The levels of culturable bioaerosols in Chinese and European cities exhibited disparities (Analysis of Variance, P < 0.01). The most dominant pathogenic bacteria and fungi were similar in Chinese (Mycobacterium: 18.2-18.9 %; Cladosporium: 23.0-30.2 %) and European cities (Mycobacterium: 15.4-37.7 %; Cladosporium: 18.1-29.3 %). Bartonella, Bordetella, Alternaria, and Aspergillus were also widely identified. BugBase analysis showed that microbiomes in China exhibited higher abundances of mobile genetic elements (MGEs) and biofilm formation capacity than those in Europe, indicating higher health risks. Through co-occurrence network analysis, heavy metals such as zinc were found to correlate with microorganism abundance; most bacteria were inversely associated, while fungi exhibited greater tolerance, indicating that heavy metals affect the growth and reproduction of bioaerosol microorganisms. This study elucidates the influence of social and environmental factors on shaping microbial community structures, offering practical insights for preventing and controlling regional bioaerosol pollution.

Seasonal distribution of human-to-human pathogens in airborne PM2.5 and their potential high-risk ARGs

Airborne microorganisms, an emerging global health threat, have attracted extensive studies. However, few attentions have been paid to the seasonal distribution of airborne pathogens, in particular their associations with antibiotic resistance genes (ARGs). To this end, two-week daily PM2.5 samples were consecutively collected from Nanchang in four seasons, and the human-to-human pathogens were screened based on high-throughput sequencing. The results showed that there were 20 pathogenic taxa in PM2.5 in Nanchang, and the highest relative abundance of pathogens was observed in winter (5.84%), followed by summer (3.51%), autumn (2.66%), and spring (1.80%). Although more than half of pathogenic taxa were shared by the four seasons, the analysis of similarities showed that pathogenic community was shaped by season (r = 0.16, p < 0.01). Co-occurrence network analysis disclosed significant interactions among pathogens in each season. Moreover, some dominant pathogens such as Plesiomonas shigelloides, Bacteroides fragilis, and Escherichia-Shigella were hub pathogens. In addition, PICRUSt2 predicted that there were 35 high-risk ARG subtypes in PM2.5, and the pathogens had strongly positive correlations with these ARGs. Even some pathogens like Plesiomonas shigelloides, Bacteroides fragilis, Aeromonas, Citrobacter, may be multi-drug resistant pathogens, including beta-lactam, aminoglycosides, chloramphenicol and multi-drug resistances, etc. Both air pollutants and meteorological conditions contributed to the seasonal variation of airborne pathogenic bacteria (r = 0.15, p < 0.01), especially CO, O3, PM2.5, temperature and relative humidity. This study furthers our understanding of airborne pathogens and highlights their associations with ARGs.

Unraveling the Pollution and Discharge of Aminophenyl Sulfone Compounds, Sulfonamide Antibiotics, and Their Acetylation Products in Municipal Wastewater Treatment Plants

Aminophenyl sulfone compounds (ASCs) are widely used in various fields, such as the pharmaceutical and textile industries. ASCs and their primary acetylation products are inevitably discharged into the environment. However, the high toxicity of ASCs could be released from the deacetylation of acetylation products. Still, the occurrence and ecological risks of ASCs and their acetylation products remain largely unknown. Here, we integrated all of the existing ASCs based on the core structure, together with their potential acetylation products, to establish a database covering 1105 compounds. By combining the database with R programming, 45 ASCs, sulfonamides, and their acetylation products were identified in the influent and effluent of 19 municipal wastewater treatment plants in 4 cities of China. 13 of them were detected for the first time in the aquatic environment, and 12 acetylation products were newly identified. The cumulative concentrations of 45 compounds in the influent and effluent were in the range of 231-9.96 × 103 and 26-2.70 × 103 ng/L, respectively. The proportion of the unrecognized compounds accounted for 60.6% of the influent and 62.8% of the effluent. Furthermore, nearly half of the ASCs (46.7%), other sulfonamides (49.9%), and their acetylation products (46.2%) were discharged from the effluent, posing a low-to-medium risk to aquatic organisms. The results provide a guideline for future monitoring programs, particularly for sulfadiazine and dronedarone, and emphasize that the ecological risk of ASCs, sulfonamides, and their acetylation products needs to be considered in the aquatic environment.

Metagenomic airborne resistome from urban hot spots through the One Health lens

Human activities are a significant contributor to the spread of antibiotic resistance genes (ARGs), which pose a serious threat to human health. These ARGs can be transmitted through various pathways, including air, within the context of One Health. This study used metagenomics to monitor the resistomes in urban air from two critical locations: a wastewater treatment plant and a hospital, both indoor and outdoor. The presence of cell-like structures was confirmed through fluorescence microscopy. The metagenomic analysis revealed a wide variety of ARGs and a high diversity of antibiotic-resistant bacteria in the airborne particles collected. The wastewater treatment plant showed higher relative abundances with 32 ARG hits per Gb and m3, followed by the main entrance of the hospital (indoor) with ≈5 ARG hits per Gb and m3. The hospital entrance exhibited the highest ARG richness, with a total of 152 different ARGs classified into nine categories of antibiotic resistance. Common commensal and pathogenic bacteria carrying ARGs, such as Moraxella, Staphylococcus and Micrococcus, were detected in the indoor airborne particles of the hospital. Interestingly, no ARGs were shared among all the samples analysed, indicating a highly variable dynamic of airborne resistomes. Furthermore, the study found no ARGs in the airborne viral fractions analysed, suggesting that airborne viruses play a negligible role in the dissemination of ARGs.

Metagenomic insights into isolable bacterial communities and antimicrobial resistance in airborne dust from pig farms

This study aims to investigate bacterial communities and antimicrobial resistance (AMR) in airborne dust from pig farms. Airborne dust, pig feces and feed were collected from nine pig farms in Thailand. Airborne dust samples were collected from upwind and downwind (25 meters from pig house), and inside (in the middle of the pig house) of the selected pig house. Pig feces and feed samples were individually collected from the pen floor and feed trough from the same pig house where airborne dust was collected. A direct total bacteria count on each sampling plate was conducted and averaged. The ESKAPE pathogens together with Escherichia coli, Salmonella, and Streptococcus were examined. A total of 163 bacterial isolates were collected and tested for MICs. Pooled bacteria from the inside airborne dust samples were analyzed using Metagenomic Sequencing. The highest bacterial concentration (1.9-11.2 × 103 CFU/m3) was found inside pig houses. Staphylococcus (n = 37) and Enterococcus (n = 36) were most frequent bacterial species. Salmonella (n = 3) were exclusively isolated from feed and feces. Target bacteria showed a variety of resistance phenotypes, and the same bacterial species with the same resistance phenotype were found in airborne dust, feed and fecal from each farm. Metagenomic Sequencing analysis revealed 1,652 bacterial species across all pig farms, of which the predominant bacterial phylum was Bacillota. One hundred fifty-nine AMR genes of 12 different antibiotic classes were identified, with aminoglycoside resistance genes (24%) being the most prevalent. A total of 251 different plasmids were discovered, and the same plasmid was detected in multiple farms. In conclusion, the phenotypic and metagenomic results demonstrated that airborne dust from pig farms contained a diverse array of bacterial species and genes encoding resistance to a range of clinically important antimicrobial agents, indicating the significant role in the spread of AMR bacterial pathogens with potential hazards to human health. Policy measurements to address AMR in airborne dust from livestock farms are mandatory.

Carbonaceous particulate matter promotes the horizontal transfer of antibiotic resistance genes

There is growing concern about the transfer of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in airborne particulate matter. In this study, we investigated the effects of various types of carbonaceous particulate matter (CPM) on the transfer of ARGs in vitro. The results showed that CPM promoted the transfer of ARGs, which was related to the concentration and particle size. Compared with the control group, the transfer frequency was 95.5, 74.7, 65.4, 14.7, and 3.8 times higher in G (graphene), CB (carbon black), NGP (nanographite powder), GP1.6 (graphite powder 1.6 micron), and GP45 (graphite powder 45 micron) groups, respectively. Moreover, the transfer frequency gradually increased with the increase in CPM concentration, while there was a negative relationship between the CPM particle size and conjugative transfer frequency. In addition, the results showed that CPM could promote the transfer of ARGs by increasing ROS, as well as activating the SOS response and expression of conjugative transfer-related genes (trbBp, trfAp, korA, kroB, and trbA). These findings are indicative of the potential risk of CPM for the transfer of ARGs in the environment, enriching our understanding of environmental pollution and further raising awareness of environmental protection.

Ambient particle composition and toxicity in 31 major cities in China

Current assessment of air quality or control effectiveness is solely based on particulate matter (PM) mass levels, without considering their toxicity differences in terms of health benefits. Here, we collected a total of 465 automobile air conditioning filters from 31 major Chinese cities to study the composition and toxicity of PM at a national scale. Dithiothreitol assay showed that normalized PM toxicity (NIOG) in different Chinese cities varied greatly from the highest 4.99 × 10-3 for Changsha to the lowest 7.72 × 10-4 for Yinchuan. NIOG values were observed to have significant correlations with annual PM10 concentration (r = -0.416, p = 0.020) and some PM components (total fungi, SO4 2- and calcium element). The concentrations of different elements and water-soluble ions in PM also varied by several orders of magnitude for 31 cities in China. Endotoxin concentrations in PM analyzed using limulus amebocyte lysate assay ranged from 2.88 EU/mg PM (Hangzhou) to 62.82 EU/mg PM (Shijiazhuang) among 31 Chinese cities. Besides, real-time qPCR revealed 10∼100-fold differences in total bacterial and fungal levels among 31 Chinese cities. The concentrations of chemical (water soluble ions and trace elements) and biological (fungi, bacteria and endotoxin) components in PM were found to be significantly correlated with some meteorological factors and gaseous pollutants such as SO2. Our results have demonstrated that PM toxicity from 31 major cities varied greatly up to 6.5 times difference; and components such as fungi and SO4 2- in PM could play important roles in the observed PM toxicity. The city-specific air pollution control strategy that integrates toxicity factors should be enacted in order to maximize health and economic co-benefits. This work also provides a comprehensive view on the overall PM pollution situation in China.

Spread of antibiotic resistance genes to Antarctica by migratory birds

Recent studies have highlighted the presence of antibiotic resistance genes (ARGs) in Antarctica, which are typically indicative of human activity. However, these studies have concentrated in the Antarctic Peninsula region, and relatively less is known about ARG prevalence in East Antarctica, where human activity levels are lower compared to the Antarctic Peninsula. In addition, the mechanisms of ARG transmission to Antarctica through natural or anthropogenic pathways remain unclear. In this study, we analyzed the fecal samples of Adélie penguins and South polar skuas by using high-throughput sequencing and microfluidic quantitative PCR to detect potential pathogens and ARGs at their breeding colonies near Syowa Station in East Antarctica. These results revealed the presence of several potential pathogens in the fecal matter of both bird species. However, the HF183 marker, which indicates human fecal contamination, was absent in all samples, as well as seawater sampled near the breeding colonies. This suggests that the human fecal contamination was negligible in our study area. In addition to pathogens, we found a significant number of ARGs and metal resistance genes in the feces of both Adélie penguins and South polar skuas, with higher detection rates in skuas than in penguins. To better understand how these birds acquire and transmit these genes, we analyzed the migratory patterns of Adélie penguins and South polar skuas by geolocator tracking. We found that the skuas migrate to the tropical and subtropical regions of the Indian Ocean during the austral winter. On the other hand, Adélie penguins exhibited a more localized migration pattern, mainly staying within Antarctic waters. Because the Indian Ocean is considered one of the major reservoirs of ARGs, South polar skuas might be exposed to ARGs during their winter migration and transfer these genes to Antarctica.

Interplay of xenobiotic-degrading and antibiotic-resistant microorganisms among the microbiome found in the air, handrail, and floor of the subway station

Investigating the quality of the subway environment, especially regarding antibiotic resistance genes (ARGs) and xenobiotics, conveys ecological and health impacts. In this study, compositions and relations of microorganisms harboring ARGs and xenobiotic degradation and metabolism genes (XDGs) in the Sukhumvit subway station (MRT-SKV) in Bangkok was assessed by analyzing the taxonomic and genetic diversity of the microbiome in the air and on the surfaces of floor and handrail. The major bacteria in the MRT-SKV (including Moraxella, which was abundant in the bioaerosol and handrail samples, and Staphylococcus, which was abundant in the bioaerosol samples) were found to contain both ARGs and XDGs. The co-abundance correlation network revealed notable relationships among bacteria harboring antibiotic resistance genes (ARGs) and xenobiotic degradation genes (XDGs). Significant associations were observed between ARGs linked to glycopeptide and fluoroquinolone resistance and genes associated with benzoate, styrene, and atrazine degradation pathways, as well as between ARGs related to cephamycin, cephalosporin, and MLS resistance and XDGs associated with the cytochrome P450-dependent drug metabolism pathway. These correlations suggested that selective pressure exerted by certain xenobiotics and antibiotics can simultaneously affect both ARGs and XDGs in the environment and should favor correlations and co-survival among ARG- and XDG-containing bacteria in the environments. The correlations may occur via shared mechanisms of resistance to both xenobiotics and antibiotics. Finally, different correlation pairs were seen in different niches (air, handrail, floor) of the subway environment or different geolocations. Thus, the relationship between ARG and XDG pairs most likely depends on the unique characteristics of the niches and on the prominent types of xenobiotics and antibiotics in the subway environment. The results indicated that interactions and connections between microbial communities can impact how they function. These microorganisms can have profound effects on accumulation of xenobiotics and ARGs in the MRT-SKV.

Airborne antibiotic and metal resistance genes - A neglected potential risk at e-waste recycling facilities

Heavy metal-rich environments can promote the selection of metal-resistance genes (MRGs) in bacteria, often leading to the simultaneous selection of antibiotic-resistance genes (ARGs) through a process known as co-selection. To comprehensively evaluate the biological pollutants at electronic-waste (e-waste) recycling facilities, air, soil, and river samples were collected at four distinct Swiss e-waste recycling facilities and analyzed for ARGs, MRGs, mobile genetic elements (MGEs), endotoxins, and bacterial species, with correlations drawn to heavy metal occurrence. To our knowledge, the present work marks the first attempt to quantify these bio-pollutants in the air of e-waste recycling facilities, that might pose a significant health risk to workers. Although ARG and MRG's profiles varied among the different sample types, intl1 consistently exhibited high relative abundance rates, identifying it as the predominant MGE across all sample types and facilities. These findings underscore its pivol role in driving diverse bacterial adaptations to extreme heavy metal exposure by selection and dissemination of ARGs and MRGs. All air samples exhibited consistent profiles of ARGs and MRGs, with blaTEM emerging as the predominant ARG, alongside pbrT and nccA as the most prevalent MRGs. However, one facility, engaged in batteries recycling and characterized by exceptionally high concentrations of heavy metals, showcased a more diverse resistance gene profile, suggesting that bacteria in this environment required more complex resistance mechanisms to cope with extreme metal exposure. Furthermore, this study unveiled a strong association between gram-negative bacteria and ARGs and less with MRGs. Overall, this research emphasizes the critical importance of studying biological pollutants in the air of e-waste recycling facilities to inform robust safety measures and mitigate the risk of resistance gene dissemination among workers. These findings establish a solid foundation for further investigations into the complex interplay among heavy metal exposure, bacterial adaptation, and resistance patterns in such distinctive ecosystems.

Residential exposure to microbial emissions from livestock farms: Implementation and evaluation of land use regression and random forest spatial models

Adverse health effects have been linked with exposure to livestock farms, likely due to airborne microbial agents. Accurate exposure assessment is crucial in epidemiological studies, however limited studies have modelled bioaerosols. This study used measured concentrations in air of livestock commensals (Escherichia coli (E. coli) and Staphylococcus species (spp.)), and antimicrobial resistance genes (tetW and mecA) at 61 residential sites in a livestock-dense region in the Netherlands. For each microbial agent, land use regression (LUR) and random forest (RF) models were developed using Geographic Information System (GIS)-derived livestock-related characteristics as predictors. The mean and standard deviation of annual average concentrations (gene copies/m3) of E. coli, Staphylococcus spp., tetW and mecA were as follows: 38.9 (±1.98), 2574 (±3.29), 20991 (±2.11), and 15.9 (±2.58). Validated through 10-fold cross-validation (CV), the models moderately explained spatial variation of all microbial agents. The best performing model per agent explained respectively 38.4%, 20.9%, 33.3% and 27.4% of the spatial variation of E. coli, Staphylococcus spp., tetW and mecA. RF models had somewhat better performance than LUR models. Livestock predictors related to poultry and pig farms dominated all models. To conclude, the models developed enable enhanced estimates of airborne livestock-related microbial exposure in future epidemiological studies. Consequently, this will provide valuable insights into the public health implications of exposure to specific microbial agents.

Heterogeneous Antibiotic Resistance Gene Removal Impedes Evaluation of Constructed Wetlands for Effective Greywater Treatment

Microorganisms carrying antimicrobial resistance genes are often found in greywater. As the reuse of greywater becomes increasingly needed, it is imperative to determine how greywater treatment impacts antimicrobial resistance genes (ARGs). Using qPCR and SmartChip™ qPCR, we characterized ARG patterns in greywater microbial communities before, during, and after treatment by a recirculating vertical flow constructed wetland. In parallel, we examined the impact of greywater-treated irrigation on soil, including the occurrence of emerging micropollutants and the taxonomic and ARG compositions of microbial communities. Most ARGs in raw greywater are removed efficiently during the winter season, while some ARGs in the effluents increase in summer. SmartChip™ qPCR revealed the presence of ARGs, such as tetracycline and beta-lactam resistance genes, in both raw and treated greywater, but most abundantly in the filter bed. It also showed that aminoglycoside and vancomycin gene abundances significantly increased after treatment. In the irrigated soil, the type of water (potable or treated greywater) had no specific impact on the total bacterial abundance (16S rRNA gene). No overlapping ARGs were found between treated greywater and greywater-irrigated soil. This study indicates ARG abundance and richness increased after treatment, possibly due to the concentration effects of the filter beds.

Antibiotic resistance in livestock, environment and humans: One Health perspective

Antibiotic resistance (AR) is a complex, multifaceted global health issue that poses a serious threat to livestock, humans, and the surrounding environment. It entails several elements and numerous potential transmission routes and vehicles that contribute to its development and spread, making it a challenging issue to address. AR is regarded as an One Health issue, as it has been found that livestock, human, and environmental components, all three domains are interconnected, opening up channels for transmission of antibiotic resistant bacteria (ARB). AR has turned out to be a critical problem mainly because of the overuse and misuse of antibiotics, with the anticipation of 10 million annual AR-associated deaths by 2050. The fact that infectious diseases induced by ARB are no longer treatable with antibiotics foreshadows an uncertain future in the context of health care. Hence, the One Health approach should be emphasized to reduce the impact of AR on livestock, humans, and the environment, ensuring the longevity of the efficacy of both current and prospective antibiotics.

Examining Antimicrobial Resistance in Escherichia coli: A Case Study in Central Virginia's Environment

While environmental factors may contribute to antimicrobial resistance (AMR) in bacteria, many aspects of environmental antibiotic pollution and resistance remain unknown. Furthermore, the level of AMR in Escherichia coli is considered a reliable indicator of the selection pressure exerted by antimicrobial use in the environment. This study aimed to assess AMR variance in E. coli isolated from diverse environmental samples, such as animal feces and water from wastewater treatment plants (WWTPs) and drainage areas of different land use systems in Central Virginia. In total, 450 E. coli isolates obtained between August 2020 and February 2021 were subjected to susceptibility testing against 12 antimicrobial agents approved for clinical use by the U.S. Food and Drug Administration. Approximately 87.8% of the tested isolates were resistant to at least one antimicrobial agent, with 3.1% showing multi-drug resistance. Streptomycin resistance was the most common (73.1%), while susceptibility to chloramphenicol was the highest (97.6%). One isolate obtained from WWTPs exhibited resistance to seven antimicrobials. AMR prevalence was the highest in WWTP isolates, followed by isolates from drainage areas, wild avians, and livestock. Among livestock, horses had the highest AMR prevalence, while cattle had the lowest. No significant AMR difference was found across land use systems. This study identifies potential AMR hotspots, emphasizing the environmental risk for antimicrobial resistant E. coli. The findings will aid policymakers and researchers, highlighting knowledge gaps in AMR-environment links. This nationally relevant research offers a scalable AMR model for understanding E. coli ecology. Further large-scale research is crucial to confirm the environmental impacts on AMR prevalence in bacteria.

Spatiotemporal Changes of Antibiotic Resistance, Potential Pathogens, and Health Risk in Kindergarten Dust

The microorganisms present in kindergartens are extremely important for children's health during their three-year preschool education. To assess the risk of outdoor dust in kindergartens, the antibiotic resistome and potential pathogens were investigated in dust samples collected from 59 kindergartens in Xiamen, southeast China in both the winter and summer. Both high-throughput quantitative PCR and metagenome analysis revealed a higher richness and abundance of antibiotic resistance genes (ARGs) in winter (P < 0.05). Besides, the bloom of ARGs and potential pathogens was evident in the urban kindergartens. The co-occurrence patterns among ARGs, mobile genetic elements (MGEs), and potential pathogens suggested some bacterial pathogens were potential hosts of ARGs and MGEs. We found a large number of high-risk ARGs in the dust; the richness and abundance of high-risk ARGs were higher in winter and urban kindergartens compared to in summer and peri-urban kindergartens, respectively. The results of the co-occurrence patterns and high-risk ARGs jointly reveal that urbanization will significantly increase the threat of urban dust to human beings and their risks will be higher in winter. This study unveils the close association between ARGs/mobile ARGs and potential pathogens and emphasizes that we should pay more attention to the health risks induced by their combination.

A database on the abundance of environmental antibiotic resistance genes

Antimicrobial resistance (AMR) poses a severe threat to global health. The wide distribution of environmental antibiotic resistance genes (ARGs), which can be transferred between microbiota, especially clinical pathogens and human commensals, contributed significantly to AMR. However, few databases on the spatiotemporal distribution, abundance, and health risk of ARGs from multiple environments have been developed, especially on the absolute level. In this study, we compiled the ARG occurrence data generated by a high-throughput quantitative PCR platform from 1,403 samples in 653 sampling sites across 18 provinces in China. The database possessed 291,870 records from five types of habitats on the abundance of 290 ARGs, as well as 8,057 records on the abundance of 30 mobile genetic elements (MGEs) from 2013 to 2020. These ARGs conferred resistance to major common types of antibiotics (a total of 15 types) and represented five major resistance mechanisms, as well as four risk ranks. The database can provide information for studies on the dynamics of ARGs and is useful for the health risk assessment of AMR.

Temporal variations of antimicrobial resistance genes in aerosols: A one-year monitoring at the puy de Dôme summit (Central France)

The recent characterization of antibiotic resistance genes (ARGs) in clouds evidenced that the atmosphere actively partakes in the global spreading of antibiotic resistance worldwide. Indeed, the outdoor atmosphere continuously receives large quantities of particles of biological origins, emitted from both anthropogenic or natural sources at the near Earth's surface. Nonetheless, our understanding of the composition of the atmospheric resistome, especially at mid-altitude (i.e. above 1000 m a.s.l.), remains largely limited. The atmosphere is vast and highly dynamic, so that the diversity and abundance of ARGs are expected to fluctuate both spatially and temporally. In this work, the abundance and diversity of ARGs were assessed in atmospheric aerosol samples collected weekly between July 2016 and August 2017 at the mountain site of puy de Dôme (1465 m a.s.l., central France). Our results evidence the presence of 33 different subtypes of ARGs in atmospheric aerosols, out of 34 assessed, whose total concentration fluctuated seasonally from 59 to 1.1 × 105 copies m-3 of air. These were heavily dominated by genes from the quinolone resistance family, notably the qepA gene encoding efflux pump mechanisms, which represented >95 % of total ARGs concentration. Its abundance positively correlated with that of bacteria affiliated with the genera Kineococcus, Neorhizobium, Devosia or Massilia, ubiquitous in soils. This, along with the high abundance of Sphingomonas species, points toward a large contribution of natural sources to the airborne ARGs. Nonetheless, the increased contribution of macrolide resistance (notably the erm35 gene) during winter suggests a sporadic diffusion of ARGs from human activities. Our observations depict the atmosphere as an important vector of ARGs from terrestrial sources. Therefore, monitoring ARGs in airborne microorganisms appears necessary to fully understand the dynamics of antimicrobial resistances in the environment and mitigate the threats they may represent.

Mobile genetic elements affect the dissemination of antibiotic resistance genes (ARGs) of clinical importance in the environment

The prevalence of antibiotic resistance genes (ARGs) in the environment is a quintessential One Health issue that threats both human and ecosystem health; however, the source and transmission of ARGs, especially clinically important ARGs (CLIARGs), in the environment have not yet been well studied. In the present study, shotgun metagenomic approaches were used to characterize the microbiome, resistome, and mobilome composition in human feces and six different environment sample types in South China. Overall, the resistome harbored 157 CLIARGs, with specific ARG hotspots (e.g., human feces, wastewater treatment plants, livestock manure and wastewater) excreting significantly higher abundance of CLIARGs compared with the natural environment. A redundancy analysis (RDA) was performed and revealed that the bacterial community compositions and mobile genetic elements (MGEs) explained 55.08% and 34.68% of the variations in ARG abundance, respectively, indicating that both bacterial community and MGEs are key contributors to the maintenance and dissemination of CLIARGs in the environment. The network analysis revealed non-random co-occurrence patterns between 200 bacterial genera and 147 CLIARGs, as well as between 135 MGEs and 123 CLIARGs. In addition to numerous co-shared CLIARGs among different sample types, the source tracking program based on the FEAST probabilistic model was used to estimate the relative contributions of the CLIARGs from potential sources to the natural environment. The source tracking analysis results delineated that mobilome, more than microbiome, contributed CLIARG transmission from those ARG hotspots into natural environment, and the MGEs in WWTPs seem to play the most significant role in the spread of CLIARGs to the natural environment (average contribution 32.9%-46.4%). Overall, this study demonstrated the distribution and dissemination of CLIARGs in the environment, and aimed to better inform strategies to control the spread of CLIARGs into the natural environment.

Antibiotic resistance genes associated with size-segregated bioaerosols from wastewater treatment plants: A review

The antibiotic-resistant pollution in size-segregated bioaerosols from wastewater treatment plants (WWTPs) is of increasing concern due to its public health risks, but an elaborate review is still lacking. This work overviewed the profile, mobility, pathogenic hosts, source, and risks of antibiotic resistance genes (ARGs) in size-segregated bioaerosols from WWTPs. The dominant ARG type in size-segregated bioaerosols from WWTPs was multidrug resistance genes. Treatment units that equipped with mechanical facilities and aeration devices, such as grilles, grit chambers, biochemical reaction tanks, and sludge treatment units, were the primary sources of bioaerosol antibiotic resistome in WWTPs. Higher enrichment of antibiotic resistome in particulate matter with an aerodynamic diameter of <2.5 μm, was found along the upwind-downwind-WWTPs gradient. Only a small portion of ARGs in inhalable bioaerosols from WWTPs were flanked by mobile genetic elements. The pathogens with multiple drug resistance had been found in size-segregated bioaerosols from WWTPs. Different ARGs or antibiotic resistant bacteria have different aerosolization potential associated with bioaerosols from various treatment processes. The validation of pathogenic antibiotic resistance bacteria, deeper investigation of ARG mobility, emission mechanism of antibiotic resistome, and development of treatment technologies, should be systematically considered in future.

Mobility, bacterial hosts, and risks of antibiotic resistome in submicron bioaerosols from a full-scale wastewater treatment plant

Antibiotic resistome could be loaded by bioaerosols and escape from wastewater or sludge to atmosphere environments. However, until recently, their profile, mobility, bacterial hosts, and risks in submicron bioaerosols (PM1.0) remain unclear. Here, metagenomic sequencing and assembly were employed to conduct an investigation of antibiotic resistome associated with PM1.0 within and around a full-scale wastewater treatment plant (WWTP). More subtypes of antibiotic resistant genes (ARGs) with higher total abundance were found along the upwind-downwind-WWTP transect. ARGs in WWTP-PM1.0 were mainly mediated by plasmids and transposases were the most prevalent mobile genetic elements (MGEs) co-occurring with ARGs. A contig-based analysis indicated that very small proportions (15.32%-19.74%) of ARGs in WWTP-PM1.0 were flanked by MGEs. Proteobacteria was the most dominant host of ARGs. A total of 28 kinds of potential pathogens, such as Pseudomonas aeruginosa and Escherichia coli, carried multiple ARG types. Compared to upwind, WWTP and corresponding downwind were characterized by higher PM1.0 resistome risk. This study emphasizes the vital role of WWTPs in discharging PM1.0-loaded ARGs and antibiotic resistant pathogens to air, and indicates the need for active safeguard procedures, such as that employees wear masks and work clothes, covering the main emission sites, and collecting and destroying of bioaerosols.

Impacts of irrigation with treated livestock wastewater on the accumulation characteristic of ARGs in the farmland soil: a case study in Hohhot, China

Irrigation with treated livestock wastewater (TWW) is a promising strategy for reusing resources. However, TWW irrigation might introduce antibiotic resistant genes (ARGs) into the soil, posing environmental risks associated with antibiotic resistance. This study focuses on investigating the influence of irrigation amounts and duration on the fate of ARGs and identifies key factors driving their changes. The results showed that there were 13 ARGs in TWW, while only 5 ARGs were detected in irrigated soil. That is some introduced ARGs from TWW could not persistently exist in the soil. After 1-year irrigation, an increase in irrigation amount from 0.016 t/m2 to 0.048 t/m2 significantly enhanced the abundance of tetC by 29.81%, while ermB and sul2 decreased by 45.37% and 76.47%, respectively (p < 0.01). After 2-year irrigation, the abundance of tetC, ermB, ermF, dfrA1, and total ARGs significantly increased (p < 0.05) when the irrigation amount increased. The abundances of ARGs after 2-year irrigation were found to be 2.5-34.4 times higher than 1 year. Obviously, the irrigation years intensified the positive correlation between ARGs abundance and irrigation amount. TetC and ermF were the dominant genes resulting in the accumulation of ARGs. TWW irrigation increased the content of organic matter and total nitrogen in the soil, which affected microbial community structure. The changes of the potential host were the determining factors driving the ARGs abundance. Our study demonstrated that continuous TWW irrigation for 2 years led to a substantial accumulation of ARGs in soil.

The antibiotic resistance reservoir of the lung microbiome expands with age in a population of critically ill patients

Antimicrobial resistant lower respiratory tract infections are an increasing public health threat and an important cause of global mortality. The lung microbiome can influence susceptibility of respiratory tract infections and represents an important reservoir for exchange of antimicrobial resistance genes. Studies of the gut microbiome have found an association between age and increasing antimicrobial resistance gene burden, however, corollary studies in the lung microbiome remain absent. We performed an observational study of children and adults with acute respiratory failure admitted to the intensive care unit. From tracheal aspirate RNA sequencing data, we evaluated age-related differences in detectable antimicrobial resistance gene expression in the lung microbiome. Using a multivariable logistic regression model, we find that detection of antimicrobial resistance gene expression was significantly higher in adults compared with children after adjusting for demographic and clinical characteristics. This association remained significant after additionally adjusting for lung bacterial microbiome characteristics, and when modeling age as a continuous variable. The proportion of adults expressing beta-lactam, aminoglycoside, and tetracycline antimicrobial resistance genes was higher compared to children. Together, these findings shape our understanding of the lung resistome in critically ill patients across the lifespan, which may have implications for clinical management and global public health.

Resistomes in freshwater bioaerosols and their impact on drinking and recreational water safety: A perspective

Antibiotic resistance genes (ARGs) are widespread environmental pollutants of biological origin that pose a significant threat to human, animal, and plant health, as well as to ecosystems. ARGs are found in soil, water, air, and waste, and several pathways for global dissemination in the environment have been described. However, studies on airborne ARG transport through atmospheric particles are limited. The ARGs in microorganisms inhabiting an environment are referred to as the "resistome". A global search was conducted of air-resistome studies by retrieving bioaerosol ARG-related papers published in the last 30 years from PubMed. We found that there is no dedicated methodology for isolating ARGs in bioaerosols; instead, conventional methods for microbial culture and metagenomic analysis are used in combination with standard aerosol sampling techniques. There is a dearth of information on the bioaerosol resistomes of freshwater environments and their impact on freshwater sources used for drinking and recreational activities. More studies of aerobiome freshwater environments are needed to ensure the safe use of water and sanitation. In this review we outline and synthesize the few studies that address the freshwater air microbiome (from tap water, bathroom showers, rivers, lakes, and swimming pools) and their resistomes, as well as the likely impacts on drinking and recreational waters. We also discuss current knowledge gaps for the freshwater airborne resistome. This review will stimulate new investigations of the atmospheric microbiome, particularly in areas where both air and water quality are of public health concern.

Distribution and major driving elements of antibiotic resistance genes in the soil-vegetable system under microplastic stress

Microplastics (MPs) and antibiotic resistance genes (ARGs) are both enriched in soil-vegetable systems as a consequence of the prolonged use of agricultural mulches. MPs can form unique bacterial communities and provide potential hosts for ARGs. Therefore, MPs stress may promote the spread of ARGs from soil to crops. Increasing ARGs pollution in soil-vegetable system. In our research, we investigated the distribution and major driving elements of antibiotic resistance genes in the soil-vegetable system under microplastic stress. The results showed that MPs treatment decreased the relative abundance of ARGs in non-rhizosphere soil. High concentrations of MPs promoted the enrichment of tetracycline antibiotic resistance genes in rhizosphere soil. MPs treatment promoted the enrichment of ARGs and mobile genetic elements (MGEs) in lettuce tissues, and the overall abundance of ARGs in root after 0.5 %, 1 %, and 2 % (w/w, dry weight) polyethylene (PE) administration was considerably higher compared to that in the untreated group (p < 0.05). At the same time, high PE concentrations promoted the spread of sulfa ARGs from root to leaf. MPs also impacted the bacterial communities in the soil-plant system, and the changes in ARGs as well as MGEs in each part of the soil-vegetable system were significantly correlated with the bacterial diversity index (p < 0.05). Correlation analysis and network analysis showed that bacterial communities and MGEs were the main drivers of ARGs variation in soil-lettuce systems.

Dynamic human exposure to airborne bacteria-associated antibiotic resistomes revealed by longitudinal personal monitoring data

Airborne antibiotic-resistant bacteria (ARB) can critically impact human health. We performed resistome profiling of 283 personal airborne exposure samples from 15 participants spanning 890 days and 66 locations. We found a greater diversity and abundance of airborne bacteria community and antibiotic resistomes in spring than in winter, and temperature contributed largely to the difference. A total of 1123 bacterial genera were detected, with 16 genera dominating. Of which, 7/16 were annotated as major antibiotic resistance gene (ARG) hosts. The participants were exposed to a highly dynamic collection of ARGs, including 322 subtypes conferring resistance to 18 antibiotic classes dominated by multidrug, macrolide-lincosamide-streptogramin, β-lactam, and fosfomycin. Unlike the overall community-level bacteria exposure, an extremely high abundance of specific ARG subtypes, including lunA and qacG, were found in some samples. Staphylococcus was the predominant genus in the bacterial community, serving as a primary bacterial host for the ARGs. The annotation of ARG-carrying contigs indicated that humans and companion animals were major reservoirs for ARG-carrying Staphylococcus. This study contextualized airborne antibiotic resistomes in the precision medicine framework through longitudinal personal monitoring, which can have broad implications for human health.

Pathogenic Bacteria Are the Primary Determinants Shaping PM2.5-Borne Resistomes in the Municipal Food Waste Treatment System

Bioaerosol pollution poses a substantial threat to human health during municipal food waste (FW) recycling. However, bioaerosol-borne antibiotic-resistant genes (ARGs) have received little attention. Herein, 48 metagenomic data were applied to study the prevalence of PM2.5-borne ARGs in and around full-scale food waste treatment plants (FWTPs). Overall, FWTP PM2.5 (2.82 ± 1.47 copies/16S rRNA gene) harbored comparable total abundance of ARGs to that of municipal wastewater treatment plant PM2.5 (WWTP), but was significantly enriched with the multidrug type (e.g., AdeC/I/J; p < 0.05), especially the abundant multidrug ARGs could serve as effective indicators to define resistome profiles of FWTPs (Random Forest accuracy >92%). FWTP PM2.5 exhibited a decreasing enrichment of total ARGs along the FWTP-downwind-boundary gradient, eventually reaching levels comparable to urban PM2.5 (1.46 ± 0.21 copies/16S rRNA gene, N = 12). The combined analysis of source-tracking, metagenome-assembled genomes (MAGs), and culture-based testing provides strong evidence that Acinetobacter johnsonii-dominated pathogens contributed significantly to shaping and disseminating multidrug ARGs, while abiotic factors (i.e., SO42-) indirectly participated in these processes, which deserves more attention in developing strategies to mitigate airborne ARGs. In addition, the exposure level of FWTP PM2.5-borne resistant pathogens was about 5-11 times higher than those in urban PM2.5, and could be more severe than hospital PM2.5 in certain scenarios (<41.53%). This work highlights the importance of FWTP in disseminating airborne multidrug ARGs and the need for re-evaluating the air pollution induced by municipal FWTP in public health terms.

Atmospheric antibiotic resistome driven by air pollutants

The atmosphere is an important reservoir and habitat for antibiotic resistance genes (ARGs) and is a main pathway to cause potential health risks through inhalation and ingestion. However, the distribution characteristics of ARGs in the atmosphere and whether they were driven by atmospheric pollutants remain unclear. We annotated 392 public air metagenomic data worldwide and identified 1863 ARGs, mainly conferring to tetracycline, MLS, and multidrug resistance. We quantified these ARG's risk to human health and identified their principal pathogenic hosts, Burkholderia and Staphylococcus. Additionally, we found that bacteria in particulate contaminated air carry more ARGs than in chemically polluted air. This study revealed the influence of typical pollutants in the global atmosphere on the dissemination and risk of ARGs, providing a theoretical basis for the prevention and mitigation of the global risks associated with ARGs.

Comprehensive profiling and risk assessment of antibiotic resistance genes in a drinking water watershed by integrated analysis of air-water-soil

The prevalence of antibiotic resistance genes (ARGs) in diverse habitats threatens public health. Watersheds represent critical freshwater ecosystems that interact with both the soil and atmosphere. However, a holistic understanding of ARGs distribution across these environmental media is currently inadequate. We profiled ARGs and bacterial communities in air-water-soil in the same watershed area during four seasons using high-throughput qPCR and 16S rRNA gene sequencing. Our findings demonstrated that aminoglycoside resistance genes (58.5%) were dominant in water, and multidrug resistance genes (55.2% and 54.2%) were dominant in soil and air. Five ARGs and nineteen bacterial genera were consistently detected in all samples, were named as shared genes or bacteria. Co-occurrence Network analysis revealed the co-occurrence module of resistance genes, mobile genetic elements (MGEs), and potential bacterial hosts, indicating that shared genes and bacteria may persist and co-spread across different environmental media. The risk assessment framework, based on ARGs' abundance, detection rate, and mobility, identified 33 high-risk ARGs. This is essential to evaluate the health risks of ARGs and to develop strategies to limit the threat of antibiotic resistance. Our study offers new insights into the risks associated with ARGs in the environment and suggests that ARGs may depend on specific bacterial cohabitants that co-exist with MGEs to facilitate their spread across environmental interfaces.

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.

Antibiotic resistome associated with inhalable bioaerosols from wastewater to atmosphere: Mobility, bacterial hosts, source contributions and resistome risk

Antibiotic resistome can be carried by the bioaerosols and propagate from wastewater treatment plants (WWTPs) to the atmosphere, but questions remain regarding their mobility, bacterial hosts, source, and resistome risk. Here, fine particulate matter (PM2.5) was collected within and around a large WWTP and analyzed by the metagenomic assembly and binning. PM2.5 was discovered with increasing enrichment of total antibiotic resistance genes (ARGs), potentially mobile ARGs, and antibiotic-resistant bacteria (ARB) along the WWTP-downwind-upwind gradient. Some ARGs were found to be flanked by certain mobile genetic elements and generally mediated by plasmids in WWTP-PM2.5. Totally, 198 metagenome assembled genomes assigning to seven phyla were identified as the ARB, and a contig-based analysis indicated that 32 pathogens were revealed harboring at least two ARGs. Despite disparate aerosolization potentials of ARGs or ARB at different WWTP units, high resistome risks were found, along with the dominant contribution of wastewater for airborne ARGs (44.79-62.82%) and ARB (35.03-40.10%). Among the detected WWTP matrices, the sludge dewatering room was characterized by the highest resistome risk associated with PM2.5. This study underscores the dispersion of ARGs and ARB from WWTPs to the atmosphere and provides a reference for managing risks of antibiotic resistance.

Titanium Dioxide Nano-Formulation: Characterization, Antimicrobial Activity, and Wound Healing in Animals

The use of metal oxide nanoparticles as an alternative antimicrobial agent has gained attention due to the increasing problem of antimicrobial resistance. Understanding its properties and potential benefits can contribute to the development of more effective and sustainable treatments in veterinary medicine. The aim of this study was to characterize TiO2-NP formulations and evaluate their antibacterial and wound healing abilities. The diameters and zeta potentials were determined using the Zetasizer in conjunction with dynamic light scattering. The agar-well diffusion method, time-kill kinetic assay and crystal violet assay were used to evaluate their antimicrobial activities. Wound healing assays were conducted both in vitro and in vivo. The study demonstrated that TiO2-NP formulations exhibit significant antimicrobial properties against various bacterial strains such as S. aureus and E. coli. No measurable E. coli growth was observed within a 15-min period following exposure to TiO2-NP formulations. The TiO2-NP formation can improve wound healing by enhancing cell migration and collagen formation in both in vitro and in vivo conditions. In summary, our study suggests that TiO2-NP has the potential for use as an antimicrobial agent for animal wound treatment due to its ability to suppress bacterial growth and biofilm formation, as well as to enhance wound healing.

Chlorine oxide radical (ClO) enables the enhanced degradation of antibiotic resistance genes during UV/chlorine treatment by selectively inducing base damage

Compared to individual UV or chlorine disinfection, the combined UV and chlorine (i.e., UV/chlorine) can substantially promote the degradation of antibiotic resistance genes (ARGs) in the effluent by generating radicals. However, the mechanisms of ARG degradation induced by radicals during UV/chlorine treatment remain largely unknown, limiting further enhancement of ARG degradation by process optimization. Herein, we aimed to uncover the role of different radicals in ARG degradation and the molecular mechanisms of ARG degradation by radicals in UV/chlorine process. The ClO was proven to be responsible for the enhanced ARG degradation during UV/chlorine treatment, while the other radicals (OH, Cl, and Cl2-) played a minor role. This is because ClO possessed both high steady-state concentration and high reactivity toward ARGs (rate constant: 4.29 × 1010 M-1 s-1). The ClO might collaborate with free chlorine to degrade ARG. The ClO degraded ARGs by selectively attacking guanine and thymine but failed to induce strand breakage, while chlorine could break the strand of ARGs. Ultimately, ClO cooperated with chlorine to degrade ARGs quickly by hydroxylation and chlorination of bases and produce many chlorine- and nitrogen-containing products as revealed by high-resolution mass spectrometry. The uncovered degradation mechanisms of ARGs by UV/chlorine provide useful guidelines for process optimization to achieve deep removal of effluent ARGs.

Drivers of Antibiotic Resistance Gene Abundance in an Urban River

In this study, we sought to profile the abundances and drivers of antibiotic resistance genes in an urban river impacted by combined sewage overflow (CSO) events. Water samples were collected weekly during the summer for two years; then, quantitative PCR was applied to determine the abundance of resistance genes associated with tetracycline, quinolones, and β-lactam antibiotics. In addition to sampling a CSO-impacted site near the city center, we also sampled a less urban site ~12 km upstream with no proximal sewage inputs. The tetracycline genes tetO and tetW were rarely found upstream, but were common at the CSO-impacted site, suggesting that the primary source was untreated sewage. In contrast, ampC was detected in all samples indicating a more consistent and diffuse source. The two other genes, qnrA and blaTEM, were present in only 40-50% of samples and showed more nuanced spatiotemporal patterns consistent with upstream agricultural inputs. The results of this study highlight the complex sources of ARGs in urban riverine ecosystems, and that interdisciplinary collaborations across diverse groups of stakeholders are necessary to combat the emerging threat of antibiotic resistance through anthropogenic pollution.

Characteristics of aerosols from swine farms: A review of the past two-decade progress

With the rapid development of large-scale and intensive swine production, the emission of aerosols from swine farms has become a growing concern, attracting extensive attention. While aerosols are found in various environments, those from swine farms are distinguished from human habitats, such as residential, suburban, and urban areas. In order to gain a comprehensive understanding of aerosols from swine farms, this paper reviewed relevant studies conducted between 2000 and 2022. The main components, concentrations, and size distribution of the aerosols were systematically reviewed. The differences between aerosols from swine farms and human living and working environments were compared. Finally, the sources, influencing factors, and reduction technologies for aerosols from swine farms were thoroughly elucidated. The results demonstrated that the concentrations of aerosols inside swine farms varied considerably, and most exceeded safety thresholds. However, further exploration is needed to fully understand the difference in airborne microorganism community structure and particles with small sizes (<1 μm) between swine farms and human living and working environments. More airborne bacterial and viruses were adhered to large particles in swine houses, while the proportion of airborne fungi in the respirable fraction was similar to that of human living and working environments. In addition, swine farms have a higher abundance and diversity of potential pathogens, airborne resistant microorganisms and resistant genes compared to the human living and working environments. The aerosols of swine farms mainly originated from sources such as manure, feed, swine hair and skin, secondary production, and waste treatment. According to the source analysis and factors influencing aerosols in swine farms, various technologies could be employed to mitigate aerosol emissions, and some end-of-pipe technologies need to be further improved before they are widely applied. Swine farms are advised not to increase aerosol concentration in human living and working environments, in order to decrease the impact of aerosols from swine farms on human health and restrain the spread of airborne potential pathogens. This review provides critical insights into aerosols of swine farms, offering guidance for taking appropriate measures to enhance air quality inside and surrounding swine farms.

The exposure risks associated with pathogens and antibiotic resistance genes in bioaerosol from municipal landfill and surrounding area

Pathogenic microbes with antibiotic resistance can thrive on municipal solid waste as nutrients and be aerosolized and transported to vicinities during waste disposal processes. However, the characterization of pathogenic bioaerosols and assessment of their exposure risks are lacking. Herein, particle size, concentration, activity, antibiotic resistance, and pathogenicity of airborne microorganisms were assessed in different sectors of a typical landfill. Results showed that active sector in downwind direction has the highest bioaerosol level (1234 CFU/m³), while residential area has the highest activity (14.82 mg/L). Botanical deodorizer from mist cannon can effectively remove bioaerosol. Most bioaerosols can be inhaled into respiratory system till bronchi with sizes ranging from 2.1-3.3 and 3.3-4.7 µm. Pathogenic bacteria (Bacilli, Bacillus, and Burkholderia-Paraburkholderia) and allergenic fungi (Aspergillus, Cladosporium, and Curvularia) prevailed in landfill. Although high abundance of microbial volatile organic compounds (mVOCs) producing bioaerosols were detected, these mVOCs contributed little to odor issues in landfill. Notably, surrounding areas have higher levels of antibiotic-resistance genes (ARGs) than inner landfill with tetC, acrB, acrF, mdtF, and bacA as dominant ones. Most ARGs were significantly correlated with bacterial community, while environmental parameters mainly influenced fungal prevalence. These findings can assist in reducing and preventing respiratory allergy or infection risks in occupational environments relating to waste management.

Occurrence of halogenated methanesulfonic acids in water and sediment from the Hangzhou Bay, China

Halogenated methanesulfonic acids (HMSAs) are an important new class of organic compounds as they were universal in the water cycle and drinking water sources. However, no study has investigated the presence of HMSAs in surface water and sediment from China. The present study reports the occurrence and spatiotemporal distribution of seven HMSAs in water and sediment samples from Hangzhou Bay, China. Trifluoromethanesulfonic acid (TFMSA) was the main contributor to the concentrations of HMSAs in water and sediment samples from spring, summer, autumn and winter which were 30.8-541 ng/L, n. d.-86.6 ng/L, 4.22-70.9 ng/L and 8.86-192 ng/L, separately, while in sediment samples were n. d.-11.1 ng/g, n. d.-12.9 ng/g, n. d.-22.5 ng/g, n. d.-4.60 ng/g, respectively. The levels of HMSAs in water from winter and spring were higher than those in summer and autumn, and the concentrations of the target HMSAs in water presents a seasonal pattern affected by the temperature, the precipitation and river flow variations. Nevertheless, the levels of HMSAs in sediment were highest in the area near the industrial area and the confluences of rivers. Correlation analysis revealed that the concentrations of TFMSA were significantly positively correlated with total organic carbon (TOC) in water samples. Although TFMSA is regarded as low toxic based on the EC₅₀ value of acute toxicity, the potential risks to aquatic ecology should be paid more attention due to its high concentrations in the aquatic system and the environmental persistency.

Enhance antibiotic resistance and human health risks in aerosols during the COVID-19 pandemic

Aerosols are an important route for the transmission of antibiotic resistance genes (ARGs). Since the 2019 (COVID-19) pandemic, the large-scale use of disinfectants has effectively prevented the spread of environmental microorganisms, but studies regarding the antibiotic resistance of airborne bacteria remain limited. This study focused on four functional urban areas (commercial areas, educational areas, residential areas and wastewater treatment plant) to study the variations in ARG abundances, bacterial community structures and risks to human health during the COVID-19 pandemic in aerosol. The results indicated the abundance of ARGs during the COVID-19 period were up to approximately 13-fold greater than before the COVID-19 period. Large-scale disinfection resulted in a decrease in total bacterial abundance. However, chlorine-resistant bacteria tended to be survived. Among the four functional areas, the diversity and abundance of aerosol bacteria were highest in commercial aera. Antibiotic susceptibility assays suggested elevated resistance of isolated bacteria to several tested antibiotics due to disinfection exposure. The potential exposure risks of ARGs to human health were 2 times higher than before the COVID-19 pandemic, and respiratory intake was the main exposure route. The results highlighted the elevated antibiotic resistance of bacteria in aerosols that were exposed to disinfectants after the COVID-19 pandemic. This study provides theoretical guidance for the rational use of disinfectants and control of antimicrobial resistance.

Prioritization, sources, and ecological risk of typical antibiotics in the Huai River, a Chinese major river: a warning about aquaculture

This is the first comprehensive report on antibiotics in the Huai River, a major Chinese river. To illuminate the concentrations, prioritization, spatial distributions, sources, and ecological risks of antibiotics, surface water samples were collected and three types of most widely used antibiotics (16 sulfonamides, 8 tetracyclines, and 14 quinolones) were analyzed. The results indicated that concentrations of ∑quinolones (86 ± 31 ng/L) > ∑tetracyclines (20 ± 13 ng/L) > ∑sulfonamides (11 ± 3.7 ng/L). Oxolinic acid (OXA), cinoxacin(CINX), norfloxacin (NFX), and methacycline (MTC) were the priority antibiotics with mean concentrations > or close to 10 ng/L, however, they were rarely included as target compounds in most previous Chinese investigations. Different spatial distributions of antibiotics were discovered across three reaches separated by two sluices, demonstrating that the sluices may impact antibiotic dissemination. According to the results of the source analysis, the aquaculture industry was the major source of observed antibiotics (49%), followed by livestock & poultry farming (26%) and mixed sources (25%). Because commercial fishing in the Huai River has been prohibited, the aquaculture industry will expand in the next years, and antibiotic contamination caused by the aquaculture industry deserves more attention. The risk quotients were calculated by comparing observed antibiotics to predicted no-effect concentrations, and the results showed that observed antibiotics posed negligible or low integrated risks for Green algae, and medium or low integrated risks for Daphnia magna.

Occurrence and influencing factors of antibiotics and antibiotic resistance genes in sediments of the largest multi-habitat lakes in Northern China

Baiyangdian Lake is a typical and largest multi-habitat lake in the North plain of China. To understand the generation and transmission of antibiotics resistance genes (ARGs) in multi-habitat lakes, the contents of nutrients (TC, TOC, TN, TP and TS), heavy metals (Zn, Cr, Ni, Cu, Pb, As, Cd and Hg), 22 antibiotics, 16S-rRNA(16S), Class I integron (intI1) and 20 ARGs were determined. Samples were taken from the Fuhe river, river estuaries, reed marshes, living area, fish ponds and open water of Baiyangdian Lake. The results showed that quinolones were the main pollutants in six habitats, and the content range was ND-104.94 ng/g. Thereinto, aac (6') -IB, blaTEM-1, ermF, qnrA, qnrD, tetG, sul1, sul2 and tetM were detected in all the analyzed samples. The absolute abundance of sul1 was the highest (5.25 × 10⁵ copies/g-6.21 × 10⁷ copies/g) in most of the samples. In these different habitats, the abundance of antibiotics and ARGs in river estuary was the highest, and that in reed marshes was the lowest. There was a significant positive correlation between the abundance of heavy metals (Cu, Pb, Zn, Ni, Cd, Hg) and the absolute abundance of 11 ARGs (P < 0.01). Redundancy analysis showed that Cu, Zn, intI1, TP and macrolides were the important factors affecting the distribution of ARGs. Our finding provides a more likely driving and influencing factor for the transmission of ARGs in lakes with complex and diverse habitats.

Colistin- and amikacin-loaded lipid-based drug delivery systems for resistant gram-negative lung and wound bacterial infections

Antimicrobial resistance (AMR) is a global health issue, which needs to be tackled without further delay. The World Health Organization(WHO) has classified three gram-negative bacteria, Pseudomonas aeruginosa, Klebsiella pneumonia and Acinetobacter baumannii, as the principal responsible for AMR, mainly causing difficult to treat nosocomial lung and wound infections. In this regard, the need for colistin and amikacin, the re-emerged antibiotics of choice for resistant gram-negative infections, will be examined as well as their associated toxicity. Thus, current but ineffective clinical strategies designed to prevent toxicity related to colistin and amikacin will be reported, highlighting the importance of lipid-based drug delivery systems (LBDDSs), such as liposomes, solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs), as efficient delivery strategies for reducing antibiotic toxicity. This review reveals that colistin- and amikacin-NLCs are promising carriers with greater potential than liposomes and SLNs to safely tackle AMR, especially for lung and wound infections.

Quantification of antibiotic resistance genes (ARGs) in clouds at a mountain site (puy de Dôme, central France)

Antibiotic resistance in bacteria is becoming a major sanitary concern worldwide. The extensive use of large quantities of antibiotics to sustain human activity has led to the rapid acquisition and maintenance of antibiotic resistant genes (ARGs) in bacteria and to their spread into the environment. Eventually, these can be disseminated over long distances by atmospheric transport. Here, we assessed the presence of ARGs in clouds as an indicator of long-distance travel potential of antibiotic resistance in the atmosphere. We hypothesized that a variety of ARGs can reach the altitude of clouds mainly located within the free troposphere. Once incorporated in the atmosphere, they are efficiently transported and their respective concentrations should differ depending on the sources and the geographical origin of the air masses. We deployed high-flow rate impingers and collected twelve clouds between September 2019 and October 2021 at the meteorological station of the puy de Dôme summit (1465 m a.s.l., France). Total airborne bacteria concentration was assessed by flow cytometry, and ARGs subtypes of the main families of antibiotic resistance (quinolone, sulfonamide, tetracycline; glycopeptide, aminoglycoside, β-lactamase, macrolide) including one mobile genetic element (transposase) were quantified by qPCR. Our results indicate the presence of 29 different ARGs' subtypes at concentrations ranging from 1.01 × 10³ to 1.61 × 10⁴ copies m^-3 of air. Clear distinctions could be observed between clouds in air masses transported over marine areas (Atlantic Ocean) and clouds influenced by continental surfaces. Specifically, quinolones (mostly qepA) resistance genes were prevalent in marine clouds (54 % of the total ARGs on average), whereas higher contributions of sulfonamide, tetracycline; glycopeptide, β-lactamase and macrolide were found in continental clouds. This study constitutes the first evidence for the presence of microbial ARGs in clouds at concentrations comparable to other natural environments. This highlights the atmosphere as routes for the dissemination of ARGs at large scale.

Seasonal variation characteristics of inhalable bacteria in bioaerosols and antibiotic resistance genes in Harbin

Bioaerosols have received extensive attention due to their impact on climate, ecological environment, and human health. This study aimed to reveal the driving factors that structure bacterial community composition and the transmission route of antibiotic resistance genes (ARGs) in PM_2.5. The results showed that the bacterial concentration in spring (8.76 × 10⁵ copies/m³) was significantly higher than that in summer (1.03 × 10⁵ copies/m³) and winter (4.74 × 10⁴ copies/m³). Low temperatures and air pollution in winter negatively affected bacterial concentrations. Keystone taxa were identified by network analysis. Although about 50 % of the keystone taxa had low relative abundances, the strong impact of complex interactions between keystone taxa and other taxa on bacterial community structure deserved attention. The bacterial community assembly was dominated by stochastic processes (79.3 %). Interactions between bacteria and environmental filtering together affected bacterial community composition. Vertical gene transfer played an important role in the transmission of airborne ARGs. Given the potential integration and expression of ARGs in recipients, the human exposure risk due to high concentrations of ARGs and mobile genetic elements cannot be ignored. This study highlights human exposure to inhalable bacterial pathogens and ARGs in urban areas.

Microbial source tracking and land use associations for antibiotic resistance genes in private wells influenced by human and livestock fecal sources

Antimicrobial resistance is a growing public health problem that requires an integrated approach among human, agricultural, and environmental sectors. However, few studies address all three components simultaneously. We investigated the occurrence of five antibiotic resistance genes (ARGs) and the class 1 integron gene (intI1) in private wells drawing water from a vulnerable aquifer influenced by residential septic systems and land-applied dairy manure. Samples (n = 138) were collected across four seasons from a randomized sample of private wells in Kewaunee County, Wisconsin. Measurements of ARGs and intI1 were related to microbial source tracking (MST) markers specific to human and bovine feces; they were also related to 54 risk factors for contamination representing land use, rainfall, hydrogeology, and well construction. ARGs and intI1 occurred in 5%-40% of samples depending on target. Detection frequencies for ARGs and intI1 were lowest in the absence of human and bovine MST markers (1%-30%), highest when co-occurring with human and bovine markers together (11%-78%), and intermediate when co-occurring with just one type of MST marker (4%-46%). Gene targets were associated with septic system density more often than agricultural land, potentially because of the variable presence of manure on the landscape. Determining ARG prevalence in a rural setting with mixed land use allowed an assessment of the relative contribution of human and bovine fecal sources. Because fecal sources co-occurred with ARGs at similar rates, interventions intended to reduce ARG occurrence may be most effective if both sources are considered.