Exposure to heavy metal and antibiotic enriches antibiotic resistant genes on the tire particles in soil

Impact of fluoroquinolone and heavy metal pollution on antibiotic resistance maintenance in aquatic ecosystems

BACKGROUND

Freshwater pollution with compounds used during anthropogenic activities could be a major driver of antibiotic resistance emergence and dissemination in environmental settings. Fluoroquinolones and heavy metals are two widely used aquatic pollutants that show a high stability in the environment and have well-known effects on antibiotic resistance selection. However, the impact of these compounds on antibiotic resistance maintenance in aquatic ecosystems remains unknown. In this study, we used a microcosm approach to determine the persistence of two fluoroquinolones (ciprofloxacin, ofloxacin) and two heavy metals (copper and zinc) in the Rhône river over 27 days. In addition, we established links between antibiotic and metal pollution, alone and in combination, and the composition of freshwater bacterial communities, the selection of specific members and the selection and maintenance of antibiotic and metal resistance genes (ARGs and MRGs) using a metagenomics approach.

RESULTS

Whereas ofloxacin was detected at higher levels in freshwater after 27 days, copper had the strongest influence on bacterial communities and antibiotic and metal resistance gene selection. In addition, heavy metal exposure selected for some ARG-harboring bacteria that contained MRGs. Our research shows a heavy metal-driven transient co-selection for fluoroquinolone resistance in an aquatic ecosystem that could be largely explained by the short-term selection of Pseudomonas subpopulations harboring both fluoroquinolone efflux pumps and copper resistance genes.

CONCLUSION

This research highlights the complexity and compound-specificity of dose-response relationships in freshwater ecosystems and provides new insights into the medium-term community structure modifications induced by overall sub-inhibitory levels of antibiotic and heavy metal pollution that may lead to the selection and maintenance of antibiotic resistance in low-impacted ecosystems exposed to multiple pollutants.

Microplastics reduced the natural attenuation of antibiotic resistance genes in fertilized soils

The prolonged application of mulch and manure in agriculture has led to significant microplastic (MP) pollution in fertilized soils, raising global concerns about its potential impacts on soil health and ecosystem function. However, the effects of MP exposure on antibiotic resistance genes (ARGs) and microbial communities in fertilized soils are unknown. Therefore, we comprehensively explored the trends and drivers of ARGs during their natural abatement under the stress of conventional and biodegradable MP addition in fertilized soils using a soil microcosm experiment and metagenomic. The findings indicated that the presence of polybutylene succinate MPs (PBS-MPs) reduced the natural attenuation rate of ARGs in fertilized soils while increasing the fraction of high-risk ARGs in soils. Microbial communities and mobile genetic elements (MGEs) mainly drove the inhibitory effect of MPs on ARG abatement. Interestingly, most potential hosts for the coexistence of ARGs, metal resistance genes (MRGs), and MGEs were annotated as pathogens, such as Escherichia spp., Salmonella spp., and Klebsiella spp. In addition, MP stress in fertilized soil may lead to long-term contamination by highly virulent and antibiotic-resistant Escherichia coli. MPs influence the distribution of carbon sources, which in turn reduces the diversity and stability of soil microbial communities, while simultaneously promoting the colonization of crucial ARG hosts, like Dyella spp. This ultimately prolonged the high-risk state for ARG proliferation in the soil. This study highlights the significant risk posed by MPs to the persistence and spread of ARGs in fertilized soils. These results provide valuable insights for managing MP contamination in agricultural systems, emphasizing the need for sustainable practices to mitigate the long-term environmental risks associated with MP pollution.

From glacier forelands to human settlements: Patterns, environmental drivers, and risks of antibiotic resistance genes

Antibiotic resistance genes (ARGs) are biological pollutants widely present in glaciers, such as ice, snow, and melt water. However, it remains unclear whether ARGs in glaciers influence their distribution in human settlements within the glacier basins. Therefore, we investigated the distribution pattern and driving factors of ARGs in the Laohugou glacier basins on the Tibetan Plateau. Using high-throughput quantitative PCR, the total abundance of ARGs in the Laohugou glacier basins ranged from 7.53 × 10⁶ to 1.83 × 10⁹ copies/g, including 128 detected ARGs across 11 classes, with aminoglycoside resistance genes being the dominant group. The abundance of ARGs exhibited a U-shaped pattern along the elevational gradient, with higher levels in glacier regions and human settlements, and the lowest abundance at mid-elevations. While glacier melting and anthropogenic disturbance are likely major contributors to this pattern, other potential mechanisms may also be involved, such as elevation-dependent microbial community composition, atmospheric deposition and release of legacy ARGs from melting permafrost and glacial ice. Together, these processes likely interact to shape the observed ARG pattern in this alpine watershed. We further verified that the distribution of ARGs was strongly correlated with microbial community structure, especially bacterial communities (r > 0.50; p < 0.05). Network analysis showed that Nitrolancea negatively correlated with several core ARGs, suggesting its potential role in regulating the spread of ARGs. Random forest analysis and structural equation modeling (SEM) indicated that, after accounting for various driving factors, organic matter and bacterial biomass were the primary drivers of increased ARG abundance. This study provides a foundation for assessing the risks of ARGs in glacier basins under global climate change, offering insights into risk mitigation strategies and guiding future ecological and public health research.

Review of Health Effects of Automotive Brake and Tyre Wear Particles

Non-exhaust emissions from brakes and tyres are becoming the major transport-related contributor of particulate matter (PM) pollution in cities. Furthermore, tyre microplastics are the major contributor of unintentionally released microplastics in all environmental compartments. The European Union introduced for the first time worldwide limits for brakes (PM10) and tyres (total abrasion mass) with the Euro 7 regulatory step. Thus, the interest in brake and tyre particles regarding health and environmental impacts has significantly increased in recent years. In this review, we summarise studies that assessed the impact of brake and tyre particles on human, mammalian, aquatic, and terrestrial cells and organisms. Furthermore, we summarise the studies that compared the impact of brake and tyre particles to other sources. We also critically examine the sampling methodologies of brake and tyre particles for health and environmental impact studies.

Effects of tire wear particles on freshwater bacterial-fungal community dynamics and subsequent elemental cycles using microcosms

Ecological impacts of tire wear particles (TWPs) on microbial communities and biogeochemical cycles in freshwater remain largely unknown. Here, we conducted a microcosm experiment to investigate interactions between the overlying water and sediment without and with TWPs addition in a rural vs. urban lake system. Our results revealed the degree of change in microbial community diversity in water is higher than that in sediment following TWPs addition. For bacterial communities, TWPs addition changed their composition in the water, but only little in the sediment. For fungal communities, TWPs addition changed their composition both in water and sediments. Furthermore, in water, TWPs addition increased network complexity between bacteria-bacteria, fungi-fungi and bacteria-fungi in the urban system but reduced it in the rural one. In contrast, TWPs presence did not significantly change network complexity among microbial communities in the sediment of both lakes. Isotope labeling analysis uncovered that based on a short-term (6 hours) incubation experiment, TWPs addition did not significantly change carbon nor nitrogen cycling in the water. Yet, certain changes could be observed, especially in the long-term experiment (1 month), indicating that TWPs pollution has the potential to impact elemental cycling and thus ecosystem functions by altering microbial communities. Our results provide new insights into TWPs-induced ecological effects on microorganisms and potential biogeochemical consequences in a rural vs. urban lakes.

Aged Microplastics and Antibiotic Resistance Genes: A Review of Aging Effects on Their Interactions

Background: Microplastic aging affects the dynamics of antibiotic resistance genes (ARGs) on microplastics, yet no review presents the effects of microplastic aging on the associated ARGs. Objectives: This review, therefore, aims to discuss the effects of different types of microplastic aging, as well as the other pollutants on or around microplastics and the chemicals leached from microplastics, on the associated ARGs. Results: It highlights that microplastic photoaging generally results in higher sorption of antibiotics and ARGs due to increased microplastic surface area and functional group changes. Photoaging produces reactive oxygen species, facilitating ARG transfer by increasing bacterial cell membrane permeability. Reactive oxygen species can interact with biofilms, suggesting combined effects of microplastic aging on ARGs. The effects of mechanical aging were deduced from studies showing larger microplastics anchoring more ARGs due to rough surfaces. Smaller microplastics from aging penetrate deeper and smaller places and transport ARGs to these places. High temperatures are likely to reduce biofilm mass and ARGs, but the variation of ARGs on microplastics subjected to thermal aging remains unknown due to limited studies. Biotic aging results in biofilm formation on microplastics, and biofilms, often with unique microbial structures, invariably enrich ARGs. Higher oxidative stress promotes ARG transfer in the biofilms due to higher cell membrane permeability. Other environmental pollutants, particularly heavy metals, antibacterial, chlorination by-products, and other functional genes, could increase microplastic-associated ARGs, as do microplastic additives like phthalates and bisphenols. Conclusions: This review provides insights into the environmental fate of co-existing microplastics and ARGs under the influences of aging. Further studies could examine the effects of mechanical and thermal MP aging on their interactions with ARGs.

A review of tire wear particles: Occurrence, adverse effects, and control strategies

Tire wear particles (TWPs), common mixed particulate emerging contaminants in the environment, have global per capita emissions accounting for 0.23-1.9 kg/year, attracting global attention recently due to their wide detection, small size, mobility, and high toxicity. This review focuses on the occurrence characteristics of TWPs in multiple environmental media, adverse effects on organisms, potential toxicity mechanisms, and environmental risk prevention and control strategies of TWPs. The environmental fate of TWPs throughout the entire process is systematically investigated by the bibliometric analysis function of CiteSpace. This review supplements the gap in the joint toxicity and related toxicity mechanisms of TWPs with other environmental pollutants. Based on the risks review of TWPs and their additives, adverse impacts have been found in organisms from aquatic environments, soil, and humans, such as the growth inhibition effect on Chironomus dilutes. A multi-faceted and rationalized prevention and control treatment of "source-process-end" for the whole process can be achieved by regulating the use of studded tires, improving the tire additive formula, growing plants roadside, encouraging micro-degradation, and other methods, which are first reviewed. By addressing the current knowledge gaps and exploring prospects, this study contributes to developing strategies for reducing risks and assessing the fate of TWPs in multiple environmental media.

Microplastics as carriers of antibiotic resistance genes and pathogens in municipal solid waste (MSW) landfill leachate and soil: a review

Landfill leachate contains antibiotic resistance genes (ARGs) and microplastics (MPs), making it an important reservoir. However, little research has been conducted on how ARGs are enriched on MPs and how the presence of MPs affects pathogens and ARGs in leachates and soil. MPs possess the capacity to establish unique bacterial populations and assimilate contaminants from their immediate surroundings, generating a potential environment conducive to the growth of disease-causing microorganisms and antibiotic resistance genes (ARGs), thereby exerting selection pressure. Through a comprehensive analysis of scientific literature, we have carried out a practical assessment of this topic. The gathering of pollutants and the formation of dense bacterial communities on microplastics create advantageous circumstances for an increased frequency of ARG transfer and evolution. Additional investigations are necessary to acquire a more profound comprehension of how pathogens and ARGs are enriched, transported, and transferred on microplastics. This research is essential for evaluating the health risks associated with human exposure to these pollutants.

Graphical Abstract

Effects of microplastics on soil microorganisms and microbial functions in nutrients and carbon cycling - A review

The harmful effects of microplastics (MPs) pollution in the soil ecosystem have drawn global attention in recent years. This paper critically reviews the effects of MPs on soil microbial diversity and functions in relation to nutrients and carbon cycling. Reports suggested that both plastisphere (MP-microbe consortium) and MP-contaminated soils had distinct and lower microbial diversity than that of non-contaminated soils. Alteration in soil physicochemical properties and microbial interactions within the plastisphere facilitated the enrichment of plastic-degrading microorganisms, including those involved in carbon (C) and nutrient cycling. MPs conferred a significant increase in the relative abundance of soil nitrogen (N)-fixing and phosphorus (P)-solubilizing bacteria, while decreased the abundance of soil nitrifiers and ammonia oxidisers. Depending on soil types, MPs increased bioavailable N and P contents and nitrous oxide emission in some instances. Furthermore, MPs regulated soil microbial functional activities owing to the combined toxicity of organic and inorganic contaminants derived from MPs and contaminants frequently encountered in the soil environment. However, a thorough understanding of the interactions among soil microorganisms, MPs and other contaminants still needs to develop. Since currently available reports are mostly based on short-term laboratory experiments, field investigations are needed to assess the long-term impact of MPs (at environmentally relevant concentration) on soil microorganisms and their functions under different soil types and agro-climatic conditions.

Potential environmental risks of field bio/non-degradable microplastic from mulching residues in farmland: Evidence from metagenomic analysis of plastisphere

The plastisphere may act as reservoir of antibiotic resistome, accelerating global antimicrobial resistance dissemination. However, the environmental risks in the plastisphere of field microplastics (MPs) in farmland remain largely unknown. Here, antibiotic resistance genes (ARGs) and virulence factors (VFs) on polyethylene microplastics (PE-MPs) and polybutylene adipate terephthalate and polylactic acid microplastics (PBAT/PLA-MPs) from residues were investigated using metagenomic analysis. The results suggested that the profiles of ARG and VF in the plastisphere of PBAT/PLA-MPs had greater number of detected genes with statistically higher values of diversity and abundance than soil and PE-MP. Procrustes analysis indicated a good fitting correlation between ARG/VF profiles and bacterial community composition. Actinobacteria was the major host for tetracycline and glycopeptide resistance genes in the soil and PE-MP plastisphere, whereas the primary host for multidrug resistance genes changed to Proteobacteria in PBAT/PLA-MP plastisphere. Besides, three human pathogens, Sphingomonas paucimobilis, Lactobacillus plantarum and Pseudomonas aeruginosa were identified in the plastisphere. The PE-MP plastisphere exhibited a higher transfer potential of ARGs than PBAT/PLA-MP plastisphere. This work enhances our knowledge of potential environmental risks posed by microplastic in farmland and provides valuable insights for risk assessment and management of agricultural mulching applications.

Effect of oxygen-containing functional groups on the micromechanical behavior of biodegradable plastics and their formation of microplastics during aging

Biodegradable plastics (BPs) are more prone to generate harmful microplastics (MPs) in a short time, which have always been ignored. Oxygenated functional group formation is considered to be a key indicator for assessing microplastic formation, while it is difficult to characterize at a very early stage. The micromechanical properties of the aging plastic during the formation of the MPs are highly influenced by the evolution of oxygen-containing functional groups, however, their relationship has rarely been revealed. Herein, we compared changes in the physicochemical properties of BPs and non-degradable plastic bags during aging in artificial seawater, soil, and air. The results showed that the oxidation of plastics in the air was the most significant, with the most prominent oxidation in BPs. The accumulation of carbonyl groups leads to a significant increase in the micromechanical properties and surface brittleness of the plastic, further exacerbating the formation of MPs. It was also verified by the FTIR, 2D-COS, AFM, and Raman spectroscopy analyses. Furthermore, the increased adhesion and roughness caused by oxygen-containing functional groups suggest that the environmental risks of BPs cannot be ignored. Our findings suggest that the testing of micromechanical properties can predicate the formation of the MPs at an early stage.

The soil plastisphere

Understanding the effects of plastic pollution in terrestrial ecosystems is a priority in environmental research. A central aspect of this suite of pollutants is that it entails particles, in addition to chemical compounds, and this makes plastic quite different from the vast majority of chemical environmental pollutants. Particles can be habitats for microbial communities, and plastics can be a source of chemical compounds that are released into the surrounding environment. In the aquatic literature, the term 'plastisphere' has been coined to refer to the microbial community colonizing plastic debris; here, we use a definition that also includes the immediate soil environment of these particles to align the definition with other concepts in soil microbiology. First, we highlight major differences in the plastisphere between aquatic and soil ecosystems, then we review what is currently known about the soil plastisphere, including the members of the microbial community that are enriched, and the possible mechanisms underpinning this selection. Then, we focus on outlining future prospects for research on the soil plastisphere.

The adsorption and release mechanism of different aged microplastics toward Hg(II) via batch experiment and the deep learning method

Aged microplastics are ubiquitous in the aquatic environment, which inevitably accumulate metals, and then alter their migration. Whereas, the synergistic behavior and effect of microplastics and Hg(II) were rarely reported. In this context, the adsorptive behavior of Hg(II) by pristine/aged microplastics involving polystyrene, polyethylene, polylactic acid, and tire microplastics were investigated via kinetic (pseudo-first and second-order dynamics, the internal diffusion model), Langmuir, and Freundlich isothermal models; the adsorption and desorption behavior was also explored under different conditions. Microplastics aged by ozone exhibited a rougher surface attached with abundant oxygen-containing groups to enhance hydrophilicity and negative surface charge, those promoted adsorption capacity of 4-20 times increment compared with the pristine microplastics. The process (except for aged tire microplastics) was dominated by a monolayer chemical reaction, which was significantly impacted by pH, salinity, fulvic acid, and co-existing ions. Furthermore, the adsorbed Hg(II) could be effectively eluted in 0.04% HCl, simulated gastric liquids, and seawater with a maximum desorption amount of 23.26 mg/g. An artificial neural network model was used to predict the performance of microplastics in complex media and accurately capture the main influencing factors and their contributions. This finding revealed that aged microplastics had the affinity to trap Hg(II) from freshwater, whereafter it released the Hg(II) once transported into the acidic medium, the organism's gastrointestinal system, or the estuary area. These indicated that aged microplastics could be the sink or the source of Hg(II) depending on the surrounding environment, meaning that aged microplastics could be the vital carrier to Hg(II).

Aging in soil increases the disturbance of microplastics to the gut microbiota of soil fauna

Microplastics (MPs) in the soil environment inevitably experience aging processes. However, how aging in soil affects MP toxicity to soil fauna remains poorly understood. In this study, two types of widely distributed MPs (polypropylene and tire wear particles) were aged in different soils, and their surface properties, morphology, leaching features of additives, biofilm colonization and toxicity to the typical soil fauna Enchytraeus crypticus were investigated. Results showed that aging in soil slightly changed the surface properties and morphology for both types of MPs, but significantly affected the release of additives, especially for those MPs aged in soil amended with manure. Moreover, a distinct and less diverse microbial community than the surrounding soils was formed on the surface of MPs, and MP type was a determinant of the biofilm microbial community. Exposure experiments indicated that aged MPs, especially those aged in soil with manure significantly affected the reproduction of soil worms with a more obvious disturbance to their gut microbiota, and biofilm features and changes in the leaching properties of MPs during aging were the main factors for these shifts. This study is the first attempt to reveal the role of aging in soil in MP toxicity to soil fauna.

Role of a typical swine liquid manure treatment plant in reducing elements of antibiotic resistance

Biological treatment of swine liquid manure may be a favorable environment for the enrichment of bacteria carrying antibiotic resistance genes (ARGs), raising the alert about this public health problem. The present work sought to investigate the performance of a swine wastewater treatment plant (SWWTP), composed of a covered lagoon biodigester (CLB) followed by three facultative ponds, in the removal of usual pollutants, antibiotics, ARGs (blaTEM, ermB, qnrB, sul1, and tetA), and intI1. The SWWTP promoted a 70% of organic matter removal, mainly by the digester unit. The facultative ponds stood out in the solids' retention carried from the anaerobic stage and contributed to ammonia volatilization. The detected antibiotic in the raw wastewater was norfloxacin (< 0.79 to 60.55 μg L-1), and the SWWTP seems to equalize peaks of norfloxacin variation probably due to sludge adsorption. CLB reduced the absolute abundance of ARGs by up to 2.5 log, while the facultative stage does not seem to improve the quality of the final effluent in terms of resistance elements. Considering the relative abundances, the reduction rates of total and ARG-carrying bacteria appear to be similar. Finally, correlation tests also revealed that organic matter and solids control in liquid manure treatment systems could help reduce the spread of ARGs after the waste final disposal.

Co-existence of polyethylene microplastics and tetracycline on soil microbial community and ARGs

Microplastics are plastic particles with particle size less than 5 mm in the environment. As an emerging organic pollutant, the presence of microplastics in the soil environment has been widely noticed. Secondly, due to the overuse of antibiotics, a large amount of antibiotics that cannot be fully absorbed by humans and livestock enter the soil environment in the form of urine or manure, making the soil suffer from serious antibiotic contamination problems. To address the environmental problems of microplastics and antibiotic contamination in soil, this study was conducted to investigate the effects of PE microplastics on antibiotic degradation, microbial community characteristics and ARGs in tetracycline-contaminated soils. The results showed that the addition of PE microplastics inhibited the degradation of tetracycline, and significantly increased the organic carbon content and decreased the neutral phosphatase activity. The addition of PE microplastics significantly reduced the alpha diversity of soil microbial community. Compared to the single tetracycline contamination. In addition, combined contamination with PE microplastics and tetracycline significantly affected bacterial genera such as Aeromicrobium, Rhodococcus, Mycobacterium and Intrasporangium. Metagenome sequencing studies revealed that the addition of PE microplastics inhibited the dissipation of ARGs in tetracycline-contaminated soils. There were strong positive correlations between Multidrug, Aminoglycoside and Clycopeptide resistance genes and Chloroflexi and Proteobacteria in tetracycline contaminated soils, and there was a strong positive correlation between Aminoglycoside resistance genes and Actinobacteria in combined contamination of PE microplastics and tetracycline. This study will provide some data support for the current environmental risk assessment of the coexistence of multiple contaminants in soil.

Metal-containing landfills as a source of antibiotic tolerance

To unveil the potential effect of metal presence to antibiotic tolerance proliferation, four sites of surface landfills containing tailings from metal processing in Slovakia (Hnúšťa, Hodruša, Košice) and Poland (Tarnowskie Góry) were investigated. Tolerance and multitolerance to selected metals (Cu, Ni, Pb, Fe, Zn, Cd) and antibiotics (ampicillin, tetracycline, chloramphenicol, and kanamycin) and interrelationships between them were evaluated. A low bacterial diversity (Shannon-Wiener index from 0.83 to 2.263) was detected in all sampling sites. Gram-positive bacteria, mostly belonging to the phylum Actinobacteria, dominated in three of the four sampling sites. The recorded percentages of tolerant bacterial isolates varied considerably for antibiotics and metals from 0 to 57% and 0.8 to 47%, respectively, among the sampling sites. Tolerances to chloramphenicol (45-57%) and kanamycin (32-45%) were found in three sites. Multitolerance to several metals and antibiotics in the range of 24 to 48% was recorded for three sites. A significant positive correlation (p < 0.05) for the co-occurrence of tolerance to each studied metal and at least one of the antibiotics was observed. Exposure time to the metal (landfill duration) was an important factor for the development of metal- as well as antibiotic-tolerant isolates. The results show that metal-contaminated sites represent a significant threat for human health not only for their toxic effects but also for their pressure to antibiotic tolerance spread in the environment.

Interactions of microplastics and soil pollutants in soil-plant systems

In recent years, increasing studies have been reported on characterization and detection of microplastics (MPs), and their interactions with organic pollutants (OPs) and heavy metals (HMs) in soils. However, a comprehensive review on the characteristics and factors that influence MPs distribution in soils, the sorption characteristics and mechanisms of soil contaminants by MPs, especially the interactions of MPs and their complexes with pollutants in the soil-plant systems remains rarely available at present. This review focuses on the sorption features and mechanisms of pollutants by MPs in soil and discussed the effects of MPs and their complexing with pollutants on soil properties, microbe and plants. The polarity of MPs significantly influenced the sorption of OPs, and different sorption mechanisms are involved for the hydrophobic and hydrophilic OPs. The sorption of OPs on MPs in soils is different from that in water. Aging of MPs can promote the sorption and migration of contaminants. The enhanced effects of biofilm in microplastisphere on the sorption of pollutants by MPs are critical, and interactions of soil environment-MPs-microbe-HMs-antibiotics increase the potential pathogens and larger release of resistance genes. The coexistence of HMs and MPs affected the growth of plants and the uptake of HMs and MPs by the plants. Moreover, the type, dose, shape and particle size of MPs have important influences on their interactions with pollutants and subsequent effects on soil properties, microbial activities and plant growth. This review also pointed out some knowledge gaps and constructive countermeasures to promote future research in this field.

Microbiota and mobile genetic elements influence antibiotic resistance genes in dust from dense urban public places

Many contaminants were carried by dust, a common environment media that is easy to contact with human beings, and antibiotic resistance genes (ARGs) as an emergency pollutant also harbor in dust and pose serious threats to human health especially those carried by opportunistic pathogens because inactivation of antibiotics caused by ARGs may enhance pathogenicity. Considering there is a gap of investigation of dust ARGs, 16 S rRNA gene sequences and high-throughput quantitative PCR were employed to obtain information of microbial communities and accumulated ARGs in dust from different urban places, including the malls, hospitals, schools and parks, to investigate the distribution and influencing factors of ARGs and discover the potential hosts of ARGs in dust. Here, 9 types of ARGs such as sulfonamide, tetracycline, and beta-lactamase and 71 subtypes of ARGs like sul1, tetM-01, and drfA1 were detected in dust. ARGs had varying distribution in different public places and seasons in dust. The abundances of total ARGs, MLSB and tetracycline genes were higher in spring than summer. The diversity of ARGs was highest in malls, follow by hospitals, schools, and parks. Additionally, multi-drug resistance genes in dust were more abundant in hospitals than in schools and parks. The microbes were distinguished as the most important driving factors for ARGs in dust, followed by the mobile genetic elements (MGEs) and different places, while dust physicochemical parameters only exert a negligible impact. Notably, several opportunistic pathogens like the Streptococcus, Vibrio, and Pseudomonas were inferred as potential hosts of high-risk ARGs such as mecA, tetM-02, and tetO-01 in dust because of strongly positive co-occurrence. These results imply that dust is likely an important reservoir of ARGs. We should realize that ARGs may be harbored in some opportunistic pathogens occur in dust and endanger human health because of dust contacting to human easily.

Can microplastics facilitate the emergence of infectious diseases?

Plastic pollution is a major environmental problem. Small plastic particles (called microplastics) have been reported to have pernicious effects on human and wildlife health, by altering physiological functions (e.g., immunity, metabolism) and interfering with commensal microorganisms. However, in addition to these direct toxic effects, we suggest that microplastic pollution might also exert deleterious effects, modifying (i) the exposure to pathogens (e.g., multi-drug resistant bacteria) and (ii) the dynamics of vector-borne diseases. Therefore, we argue that microplastics should be considered as a ubiquitous environmental hazard, potentially promoting the (re)emergence of infectious diseases. The implementation of multi- and interdisciplinary research projects are crucial to properly evaluate if microplastic pollution should be added to the current list of global health threats.