Antibiotic resistomes in face-mask biofilm along an urban river: Multiple drivers and co-occurrence with human opportunistic pathogens

Antibiotic resistance genes and virulence factors in the plastisphere in wastewater treatment plant effluent: Health risk quantification and driving mechanism interpretation

Microplastics (MPs) are ubiquitous in wastewater treatment plants (WWTPs) and provide a unique niche for the spread of pollutants. To date, risk assessments and driving mechanisms of pathogens, antibiotic resistance genes (ARGs), and virulence factors (VFs) in the plastisphere are still lacking. Here, the microbiota, ARGs, VFs, their potential health risks, and biologically driving mechanisms on polythene (PE), polyethylene terephthalate (PET), poly (butyleneadipate-co-terephthalate) and polylactic acid blends (PBAT/PLA), PLA MPs, and gravel in WWTP effluent were investigated. The results showed that plastisphere and gravel biofilm harbored more distinctive microorganisms, promoting the uniqueness of pathogens, ARGs, and VFs compared to WWTP effluent. The abundance of major pathogens, ARGs, and VFs in the plastisphere was 1.01-1.35 times higher than that in the effluent. The high health risk of ARGs (HRA) calculated by fully considering the abundance, clinical relevance, pathogenicity, accessibility and mobility, and the high proportion of resistance contigs with mobile genetic elements confirmed that the plastisphere posed the highest potential health risk. Candidatus Microthrix and Candidatus Promineifilum were the essential hosts of ARGs and VFs in the plastisphere and gravel biofilm, respectively. High metabolic activity such as amino acid metabolism and biosynthesis of secondary metabolites, and highly expressed key genes increased the synthesis of ARGs and VFs. The primary mechanisms driving ARG enrichment in the plastisphere were enhanced microbial metabolic activity, increased frequency of horizontal gene transfer, heightened antibiotic inactivation and efflux, and reduced cell permeability. This study provided new insights into the ARGs, VFs, and health risks of the plastisphere and emphasized the importance of strict control of wastewater discharge.

Microbial communities and mobile genetic elements determine the variations of antibiotic resistance genes for a continuous year in the urban river deciphered by metagenome assembly

Antibiotic resistance genes (ARGs) have become emerging environmental contaminants influenced by intricate regulatory factors. However, there is a lack of comprehensive studies on the evolution and distribution of ARGs over a full year in urban rivers, which serve as significant reservoirs of ARGs due to dynamic human activities. In this study, we conducted a 12-month metagenomic assembly to explore the microbial communities, ARGs, mobile genetic elements (MGEs) coexisting with ARGs, ARGs hosts, and the impact of environmental factors. Bacitracin (32%-47%) and multidrug (13%-24%) were detected throughout the year, constituting over 60% of the total abundance, making them the primary ARGs types. The assembly mechanisms of microbial communities and ARGs were primarily driven by stochastic processes. Integrase, IntI1, recombinase, and transposase were identified as the main MGEs coexisting with ARGs. Procrustes analysis revealed a significant structural association, indicating that the composition of host communities likely plays crucial roles in the seasonal composition and distribution of ARGs. Human pathogenic bacteria (HPBs) were identified in the summer, autumn, and winter, with Escherichia coli, Klebsiella pneumoniae, Acinetobacter lwoffii, and Burkholderiales bacterium being the primary HPBs. Mantle tests and PLS-PM equation analysis indicated that microbial communities and MGEs are the most critical factors determining the distribution and composition of ARGs in the river. Environmental factors (including water properties and nutrients) and ARGs hosts influence the evolution and abundance of ARGs by directly regulating microbial communities and MGEs. This study provides critical insights into risk assessment and management of ARGs in urban rivers.

Distinct species turnover patterns shaped the richness of antibiotic resistance genes on eight different microplastic polymers

Elucidating the formation mechanism of plastisphere antibiotic resistance genes (ARGs) on different polymers is necessary to understand the ecological risks of plastisphere ARGs. Here, we explored the turnover and assembly mechanism of plastisphere ARGs on 8 different microplastic polymers (4 biodegradable (bMPs) and 4 non-biodegradable microplastics (nMPs)) by metagenomic sequencing. Our study revealed the presence of 479 ARGs with abundance ranging from 41.37 to 58.17 copies/16S rRNA gene in all plastispheres. These ARGs were predominantly multidrug resistance genes. The richness of plastisphere ARGs on different polymers had a significant correlation with the contribution of species turnover to plastisphere ARGs β diversity. Furthermore, polymer type was the most critical factor affecting the composition of plastisphere ARGs. More opportunistic pathogens carrying diverse ARGs on BMPs (PBAT, PBS, and PHA) with higher horizontal gene transfer potential may further magnify the ecological risks and human health threats. For example, the opportunistic pathogens Riemerella anatipestifer, Vibrio campbellii, and Vibrio cholerae are closely related to human production and life, which were the important potential hosts of many plastisphere ARGs and mobile genetic elements on BMPs. Thus, we emphasize the urgency of developing the formation mechanism of plastisphere ARGs and the necessity of controlling BMPs and ARG pollution, especially BMPs, with ever-increasing usage in daily life.

Temporal changes in the morphological and microbial diversity of biofilms on the surface of a submerged stone in the Danube River

Epilithic biofilms are ubiquitous in large river environments and are crucial for biogeochemical processes, but their community structures and functions remain poorly understood. In this paper, the seasonal succession in the morphological structure and the taxonomic composition of an epilithic bacterial biofilm community at a polluted site of the Danube River were followed using electron microscopy, high-throughput 16S rRNA gene amplicon sequencing and multiplex/taxon-specific PCRs. The biofilm samples were collected from the same submerged stone and carried out bimonthly in the littoral zone of the Danube River, downstream of a large urban area. Scanning electron microscopy showed that the biofilm was composed of diatoms and a variety of bacteria with different morphologies. Based on amplicon sequencing, the bacterial communities were dominated by the phyla Pseudomonadota and Bacteroidota, while the most abundant archaea belonged to the phyla Nitrososphaerota and Nanoarchaeota. The changing environmental factors had an effect on the composition of the epilithic microbial community. Critical levels of faecal pollution in the water were associated with increased relative abundance of Sphaerotilus, a typical indicator of "sewage fungus", but the composition and diversity of the epilithic biofilms were also influenced by several other environmental factors such as temperature, water discharge and total suspended solids (TSS). The specific PCRs showed opportunistic pathogenic bacteria (e.g. Pseudomonas spp., Legionella spp., P. aeruginosa, L. pneumophila, Stenotrophomonas maltophilia) in some biofilm samples, but extended spectrum β-lactamase (ESBL) genes and macrolide resistance genes could not be detected.

Effect of baicalin on eradicating biofilms of bovine milk derived Acinetobacter lwoffii

BACKGROUND

Acinetobacter lwoffii (A.lwoffii) is a serious zoonotic pathogen that has been identified as a cause of infections such as meningitis, bacteremia and pneumonia. In recent years, the infection rate and detection rate of A.lwoffii is increasing, especially in the breeding industry. Due to the presence of biofilms, it is difficult to eradicate and has become a potential super drug-resistant bacteria. Therefore, eradication of preformed biofilm is an alternative therapeutic action to control A.lwoffii infection. The present study aimed to clarify that baicalin could eradicate A.lwoffii biofilm in dairy cows, and to explore the mechanism of baicalin eradicating A.lwoffii.

RESULTS

The results showed that compared to the control group, the 4 MIC of baicalin significantly eradicated the preformed biofilm, and the effect was stable at this concentration, the number of viable bacteria in the biofilm was decreased by 0.67 Log10CFU/mL. The total fluorescence intensity of biofilm bacteria decreased significantly, with a reduction rate of 67.0%. There were 833 differentially expressed genes (367 up-regulated and 466 down-regulated), whose functions mainly focused on oxidative phosphorylation, biofilm regulation system and trehalose synthesis. Molecular docking analysis predicted 11 groups of target proteins that were well combined with baicalin, and the content of trehalose decreased significantly after the biofilm of A.lwoffii was treated with baicalin.

CONCLUSIONS

The present study evaluated the antibiofilm potential of baicalin against A.lwoffii. Baicalin revealed strong antibiofilm potential against A.lwoffii. Baicalin induced biofilm eradication may be related to oxidative phosphorylation and TCSs. Moreover, the decrease of trehalose content may be related to biofilm eradication.

The critical role of microplastics in the fate and transformation of sulfamethoxazole and antibiotic resistance genes within vertical subsurface-flow constructed wetlands

Constructed wetlands (CWs) are reservoirs of microplastics (MPs) in the environment. However, knowledge about the impact of MPs on antibiotic removal and the fate of antibiotic resistance genes (ARGs) is limited. We focused on sulfamethoxazole (SMX) as a representative compound to examine the effects of MPs on SMX removal and the proliferation and dissemination of two SMX-related ARGs (sul1 and sul2) in vertical subsurface-flow CW (VFCW) microcosm. The presence of MPs in the substrate was found to enhance the proliferation of microorganisms owing to the large specific surface area of the MPs and the release of dissolved organic carbon (DOC) on MP surfaces, which resulted in a high SMX removal ranging from 97.80 % to 99.80 %. However, the presence of MPs promoted microbial interactions and the horizontal gene transfer (HGT) of ARGs, which led to a significant increase in the abundances of sul1 and sul2 of 68.47 % and 17.20 %, respectively. It is thus imperative to implement rigorous monitoring strategies for MPs to mitigate their potential ecological hazards.

Dynamic evolution of antibiotic resistance genes in plastisphere in the vertical profile of urban rivers

Microplastics (MPs) can vertically transport in the aquatic environment due to their aging and biofouling, forming distinct plastisphere in different water layers. However, even though MPs have been regarded as hotspots for antibiotic resistance genes (ARGs), little is known about the propagation and transfer of ARGs in plastisphere in waters, especially in the vertical profile. Therefore, this study investigated the dynamic responses and evolution of ARGs in different plastisphere distributed vertically in an urbanized river. The biofilm biomass in the polylactic acid (PLA) plastisphere was relatively higher than that in the polyethylene terephthalate (PET), showing depth-decay variations. The ARGs abundance in plastisphere were much higher than that in the surrounding waters, especially for the PLA. In the vertical profiles, the ARGs abundance in the PET plastisphere increased with water depths, while the highest abundance of ARGs in the PLA mostly appeared at intermediate waters. In the temporal dynamic, the ARGs abundance in plastisphere increased and then decreased, which may be dominated by the MP types at the initial periods. After long-term exposure, the influences of water depths seemed to be strengthened, especially in the PET plastisphere. Compared with surface waters, the microbiota attached in plastisphere in deep waters showed high species richness, strong diversity, and complex interactions, which was basically consistent with the changes of nutrient contents in different water layers. These vertical variations in microbiota and nutrients (e.g., nitrogen) may be responsible for the propagation of ARGs in plastisphere in deep waters. The host bacteria for ARGs in plastisphere was also developed as water depth increased, leading to an enrichment of ARGs in deep waters. In addition, the abundance of ARGs in plastisphere in bottom waters was positively correlated with the mobile genetic elements (MGEs) of intI1 and tnpA05, indicative of a frequent horizontal gene transfer of ARGs. Overall, water depth played a critical role in the propagation of ARGs in plastisphere, which should not be ignored in a long time series. This study provides new insights into the dynamic evolution of ARGs propagation in plastisphere under increasing global MPs pollution, especially in the vertical profile.

Selection for antimicrobial resistance in the plastisphere

Microplastics and antimicrobials are widespread contaminants that threaten global systems and frequently co-exist in the presence of human or animal pathogens. Whilst the impact of each of these contaminants has been studied in isolation, the influence of this co-occurrence in driving antimicrobial resistance (AMR)1 in microplastic-adhered microbial communities, known as 'the Plastisphere', is not well understood. This review proposes the mechanisms by which interactions between antimicrobials and microplastics may drive selection for AMR in the Plastisphere. These include: 1) increased rates of horizontal gene transfer in the Plastisphere compared with free-living counterparts and natural substrate controls due to the proximity of cells, co-occurrence of environmental microplastics with AMR selective compounds and the sequestering of extracellular antibiotic resistance genes in the biofilm matrix. 2) An elevated AMR selection pressure in the Plastisphere due to the adsorbing of AMR selective or co-selective compounds to microplastics at concentrations greater than those found in surrounding mediums and potentially those adsorbed to comparator particles. 3) AMR selection pressure may be further elevated in the Plastisphere due to the incorporation of antimicrobial or AMR co-selective chemicals in the plastic matrix during manufacture. Implications for both ecological functioning and environmental risk assessments are discussed, alongside recommendations for further research.

Face mask derived micro(nano)plastics and organic compounds potentially induce threat to aquatic ecosystem security revealed by toxicogenomics-based assay

Micro(nano)plastics widely detected in aquatic environments have caused serious threat to water quality security. However, as a potential important source of micro(nano)plastics in surface water during the COVID-19 pandemic, the ecological risks of face mask waste to aquatic environments remain poorly understood. Herein, we comprehensively characterized the micro(nano)plastics and organic compounds released from four daily used face masks in aqueous environments and further evaluated their potential impacts on aquatic ecosystem safety by quantitative genotoxicity assay. Results from spectroscopy and high-resolution mass spectrum showed that plastic microfibers/particles (∼11%-83%) and leachable organic compounds (∼15%-87%) were dominantly emitted pollutants, which were significantly higher than nanoplastics (< ∼5%) based on mass of carbon. Additionally, a toxicogenomics approach using green fluorescence protein-fused whole-cell array revealed that membrane stress was the primary response upon the exposure to micro(nano)plastics, whereas the emitted organic chemicals were mainly responsible for DNA damage involving most of the DNA repair pathways (e.g., base/nucleotide excision repair, mismatch repair, double-strand break repair), implying their severe threat to membrane structure and DNA replication of microorganisms. Therefore, the persistent release of discarded face masks derived pollutants might exacerbate water quality and even adversely affect aquatic microbial functions. These findings would contribute to unraveling the potential effects of face mask waste on aquatic ecosystem security and highlight the necessity for more developed management regulations in face mask disposal.