The Bacterial Mobile Resistome Transfer Network Connecting the Animal and Human Microbiomes

Evaluation of probiotic properties and safety of a Bacillus strain for shrimp farming: Integrating in vitro testing, genomic analysis and in vivo validation

This study evaluated the probiotic properties and safety of Bacillus subtilis subsp. inaquosorum BSXE-2102 through in vitro testing, genomic analysis, and in vivo validation in shrimp farming. In vitro assays revealed the potent antagonistic activity of BSXE-2102 against 8 aquatic pathogenic strains. Genomic analysis of BSXE-2102 unveiled multiple genes responsible for the biosynthesis of 12 secondary metabolites, indicating its potential in combating pathogens. The identification of stress tolerance and adhesion-related genes suggested that BSXE-2102 has the ability to survive and colonize the host environment. The presence of numerous genes involved in the metabolism of carbohydrates, lipids, and amino acids, as well as the biosynthesis of 13 amino acids, 5 organic acids, and 7 vitamins, highlighted its role in food digestion and nutrition provision. Additionally, genes related to immune stimulation were identified, underscoring its potential immunomodulatory effects. Safety assessments, including antibiotic resistance tests, hemolytic assays, and genomic analyses, indicated that BSXE-2102 was sensitive to all antibiotics tested and did not carry high-risk antibiotic resistance genes. The strain also exhibited no hemolytic activity and lacked high-risk virulence factor-coding genes. The in vivo feeding experiment demonstrated that dietary supplementation with BSXE-2102 (at concentrations of 1 × 105, 1 × 106, 1 × 107, and 1 × 108 CFU/g) improved growth performance, enhanced 8 serological immune parameters, upregulated the expression levels of 8 hepatopancreatic immune-related genes, and increased resistance against Vibrio parahaemolyticus of Penaeus vannamei to varying degrees. These results were consistent with the findings from in vitro assays and genomic analyses. Collectively, the in vitro, genomic, and in vivo findings supported the safe use of B. subtilis BSXE-2102 as a potential probiotic to enhance the growth performance, immune capacity, and disease resistance of P. vannamei. A supplementation concentration of 1 × 107-8 CFU/g for the strain in shrimp feed is recommended.

Different fates between extracellular and intracellular antimicrobial resistome in full-scale activated sludge and membrane bioreactor processes

Treated effluent of wastewater treatment plants (WWTPs) are major sources of extracellular antimicrobial resistance genes (eARGs) into aquatic environments. This study aimed to clarify the fate and origins of eARGs from influent to treated effluent at a full-scale WWTP. The compositions of eARG and intracellular ARG (iARG) were acquired via shotgun metagenomic sequencing in influent wastewater, activated sludge, and treated effluent of the target WWTP, where identical wastewater was treated by conventional activated sludge (CAS) and membrane bioreactor (MBR) processes. The proportion of eARGs to iARGs increased from influent to effluent in both processes, reaching almost half of the total ARG. Most eARGs in influent were associated with clinically important antimicrobials, whereas eARGs in sludge and effluent were dominated by aminoglycoside resistance genes of aadA and APH variants. Although the eARGs composition in influent wastewater mirrored that of iARGs, a substantial shift occurred in activated sludge and effluent, highlighting the presence of distinct dissemination and reduction mechanisms between eARGs and iARGs. Notably, the origin of eARGs in treated effluent was mainly iARGs in the effluent rather than the carryover of eARG from activated sludge, which were substantially reduced in MBR, compared to CAS. Consequently, these differences in selective mechanisms led to different fates between eARG and iARG during wastewater treatment.

Extended-Spectrum-Beta-Lactamase (ESBL)-Producing Escherichia coli in Laying Hens: Slaughterhouse Prevalence and Antibiotic Resistance Patterns

Background: Laying hens, which are widely utilized for consumption and export in various regions, experience prolonged antibiotic exposure due to their longer lifespan, increasing the risk of antibiotic resistance and impacting the microbial environment of poultry slaughterhouses. Given the significance of extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli in food safety, this study aimed to investigate the prevalence of ESBL genes in E. coli isolated from a laying hen slaughterhouse in Konya, Turkey. Methods: Sampling was conducted using a convenient sampling approach, and a total of 150 samples were collected from a single slaughterhouse over six visits during both warm (June-August) and cold (January-March) seasons to evaluate seasonal variations. Samples were categorized into environmental sources (personnel, air, wastewater, eggs) and carcass-related sources (cloaca, carcasses at critical control points, final product). Classical cultural and molecular techniques and antimicrobial susceptibility tests were used for ESBL presence and gene characterization. For sequence analysis, the bidirectional Sanger Gene sequence analysis method was applied. Results: PCR-based detection identified 10 of the 17 isolates as E. coli by amplifying the uspA gene, and bidirectional Sanger sequencing further confirmed these isolates at the species level. The E. coli isolates were detected at various sampling areas, including personnel, carcasses after evisceration, and raw wastewater samples collected at different time points. In the multiplex PCR analysis, most ESBL isolates were positive for the blaCTX-M gene. The co-existence of blaTEM and blaCTX-M genes was detected in five samples. Additionally, three genes (blaSHV, blaCTX-M, and blaOXA) were identified in a carcass sample after evisceration. All ESBL-producing isolates harbored the blaCTX-M1 gene, and multiple antibiotic resistance was observed across all isolates. The presence of these genes was strongly associated with resistance to ampicillin, amoxicillin-clavulanic acid, aztreonam, cefepime, cefpodoxime, cefuroxime, and cephalothin, highlighting the critical role of blaCTX-M in driving the multidrug resistance patterns observed in this study. The highest resistance rate (80%) was observed in "personnel" and "carcass samples after evisceration", while all isolates remained sensitive to carbapenems (imipenem and meropenem). Conclusions: Our findings highlight the importance of the laying hen slaughter line as a potential source of contamination with ESBL-producing E. coli, which poses significant implications for food safety and public health. These findings underscore the need for improved control measures to mitigate ESBL E. coli transmission in poultry processing and highlight the importance of optimizing antibiotic use strategies in laying hen farming.

CARPDM: cost-effective antibiotic resistome profiling of metagenomic samples using targeted enrichment

Better interrogation of antimicrobial resistance requires new approaches to detect the associated genes in metagenomic samples. Targeted enrichment is an ideal method for their sequencing and characterization. However, no open-source, up-to-date hybridization probe set targeting antimicrobial resistance genes exists. Here, we describe the Comprehensive Antibiotic Resistance Probe Design Machine (CARPDM), a probe design software package made to run alongside all future Comprehensive Antibiotic Resistance Database releases. To test its efficacy, we have created and tested two separate probe sets: allCARD, which enriches all genes encoded in the Comprehensive Antibiotic Resistance Database's protein homolog models (n = 4,661), and clinicalCARD, which focuses on a clinically relevant subset of resistance genes (n = 323). We demonstrate that allCARD increases the number of reads mapping to resistance genes by up to 594-fold. clinicalCARD performs similarly when clinically relevant genes are present, increasing the number of resistance-gene mapping reads by up to 598-fold. In parallel with this development, we have established a protocol to synthesize any probe set in-house, saving up to 350 dollars per reaction. Together, these probe sets, their associated design program CARPDM, and the protocol for in-house synthesis will democratize metagenomic resistome analyses, allowing researchers access to a cost-effective and efficient means to explore the antibiotic resistome.IMPORTANCEAntimicrobial resistance threatens to undermine all modern medicine and is driven by the spread of antimicrobial resistance genes among pathogens, environments, patients, and animals. DNA sequencing of complex samples, such as wastewater, shows considerable promise for tracking these genes and making risk assessments. However, these methods suffer from high costs and low detection limits, plus a requirement for frequent redesign due to the constantly evolving diversity of resistance genes. Building upon our Comprehensive Antibiotic Resistance Database, our research provides software for on-demand renewal, based on the latest knowledge of resistance gene diversity, of our novel bait-capture hybridization platform that simultaneously reduces cost and increases detection levels for DNA sequencing of complex samples. The significance of our research is in the development of new software tools, reagent synthesis protocols, and hybridization enrichment protocols to provide affordable, high-resolution metagenomics DNA sequencing, which we test using environmental and wastewater samples.

Genome Analysis of 6222 Bacterial Isolates from Livestock and Food Environments in Spain to Decipher the Antibiotic Resistome

Background/Objectives: Antimicrobial resistance (AMR) poses a significant threat to global health and the economy, with projected costs ranging from $300 billion to $1 trillion annually and an estimated 10 million deaths per year by 2050. The food chain, from primary production to retail, represents a critical entry point for antimicrobial resistant bacteria into communities. This underscores the need for a coordinated "One Health" approach, integrating efforts in animal production, environmental health, and human healthcare to address this global concern. This study aimed to characterize the global resistome in Spanish primary production by sequencing 6222 bacterial genomes from animal origin. Methods and Results: Whole genome sequencing was performed on bacterial isolates collected from various farms and analyzed using a validated bioinformatic pipeline. The analysis revealed a diverse range of bacterial species, with Enterobacteriaceae being the most prevalent family. Escherichia coli was the most common species, followed by Salmonella enterica and Pseudomonas aeruginosa. This study identified 1072 antimicrobial resistance genes coding for 43 different classes of resistance, potentially conferring resistance to 81 antimicrobials. Additionally, 79 different plasmid types were detected, highlighting the potential for horizontal gene transfer. Conclusions: The resistome analysis revealed genes conferring resistance to various antibiotic classes, as well as antiseptics, disinfectants, and efflux pump-mediated resistance. This comprehensive characterization of AMR genes circulating in bacteria from primary production provides crucial insights into the ecology of AMR in Spanish livestock.

Co-resistance is the dominant mechanism of co-selection and dissemination of antibiotic resistome in nano zinc oxide polluted soil

The broader soil bacterial community responses at ecotoxicologically relevant levels of nano ZnO (nZnO) focussing on co-selection of antibiotic resistance (AR) were investigated. nZnO imposed a stronger influence than the bulk counterpart (bZnO) on antibiotic resistance genes (ARGs) with multidrug resistance (MDR) systems being predominant (63 % of total ARGs). Proliferation of biomarker ARGs especially for last resort antibiotic like vancomycin was observed and Streptomyces hosted multiple ARGs. nZnO was the major driver of the resistome with efflux systems dominating the AR mechanism. Environmental risk associated with nZnO was mediated through metal driven co-selection of ARGs and their probable transfer to eukaryotic hosts through horizontal gene transfer (HGT) via mobile genetic elements (MGEs). Novel resistance genes tetA, mdtA, int and tnpA validated in our study can be used as biomarkers for rapid detection of nZnO toxicity in soils. qRT-PCR validation of resistome in the rhizosphere soil microbiome of turmeric indicated that Zn levels decreased by 16 % compared to bulk soil with 80 % bioaccumulation in rhizomes at 1000 mg Zn kg-1 and subsequent down regulation of ARGs. Expression of key biosynthetic genes for curcumin in turmeric rhizomes showed an increase up to 500 mg Zn kg-1 as nZnO. Validation of co-selection phenomenon in microcosm with 10 mg kg-1 tetracycline without added Zn indicated 20 % upregulation of Zn resistance genes (ZRGs) like czcA, yiip and zntA.

Acquired Bacterial Resistance to Antibiotics and Resistance Genes: From Past to Future

The discovery, commercialization, and regular administration of antimicrobial agents have revolutionized the therapeutic paradigm, making it possible to treat previously untreatable and fatal infections. However, the excessive use of antibiotics has led to develop resistance soon after their use in clinical practice, to the point of becoming a global emergency. The mechanisms of bacterial resistance to antibiotics are manifold, including mechanisms of destruction or inactivation, target site modification, or active efflux, and represent the main examples of evolutionary adaptation for the survival of bacterial species. The acquirement of new resistance mechanisms is a consequence of the great genetic plasticity of bacteria, which triggers specific responses that result in mutational adaptation, acquisition of genetic material, or alteration of gene expression, virtually producing resistance to all currently available antibiotics. Understanding resistance processes is critical to the development of new antimicrobial agents to counteract drug-resistant microorganisms. In this review, both the mechanisms of action of antibiotic resistance (AMR) and the antibiotic resistance genes (ARGs) mainly found in clinical and environmental bacteria will be reviewed. Furthermore, the evolutionary background of multidrug-resistant bacteria will be examined, and some promising elements to control or reduce the emergence and spread of AMR will be proposed.

Impact of different continuous fertilizations on the antibiotic resistome associated with a subtropical triple-cropping system over one decade

The prevalence of antibiotic resistance genes (ARGs) in agricultural soils has garnered significant attention. However, the long-term impacts of various nitroge (N)-substitution fertilization regimes on the distribution of soil ARGs and their dominant drivers in a subtropical triple-cropping system remain largely unexplored. This study employed a metagenomic approach to analyze soil ARGs, microbial communities, mobile genetic elements (MGEs), and viruses from a maize-maize-cabbage rotation field experiment with five different fertilization regimes. Soil samples were collected in 2012 and 2021. A total of 615 unique ARG subtypes were identified, with multidrug, bacitracin, and rifamycin resistance genes being the most abundant. Notably, ARG types. the continuous application of fresh chicken manure (CM) over 10 years significantly increased both the count of unique ARG subtypes and the total ARG abundance compared to other fertilization regimes, such as inorganic fertilizer and composted chicken manure. Specifically, the abundance of genes associated with antibiotic target replacement (e.g., sul1 and sul2) in the CM-treated soil rose by 8.83-fold from 2021 to 2012. Our random forest analysis revealed that the abundance of three MGEs (QacEdelta, plasmids, and IstB), two viral families (Myoviridae and Podoviridae), two bacterial phyla (Chloroflexi and Planctomycetes), and two environmental factors (pH and soil organic matter (SOM)) significantly influenced the distribution of ARGs. Furthermore, variance decomposition analysis underscored the critical roles of the three MGEs and the two viral families in the dissemination of ARGs, suggesting that horizontal gene transfer (HGT) may play a key role in ARG spread. These findings enhance our understanding of how different fertilization practices influence ARG dissemination in subtropical triple-cropping agroecosystems over the long term and provide valuable insights for optimizing fertilization management strategies.

Comparative analysis of fungal and bacterial composition in natural wines and their closest pesticide-treated counterparts

Fermentation produces diverse consumables like bread, wine, beer, and cheese, with fungi playing a key role. This study sequenced fungal and bacteria DNA from 46 commercial wines, paired by vineyard proximity, harvest time, and grape variety. One in each pair was natural, while the other had pesticide treatments and microbial adjunctions. Bacteria profiles were studied using targeted sequencing of the V3-V4 region of the 16 S rRNA gene while fungal profiles were studied with ITS gene targeted sequencing. Significant variability was observed in the microbial content of these wines. We identified 19 unique fungal species in natural wines, absent in pesticide-treated ones. Some have known health roles. The most abundant was Penicillium jiangxiense in Lot-et-Garonne, known for its antitumor properties. Hyphopichia pseudoburtonii, with notable aromatic properties, was also detected, commonly found in insect and fish microbiota. Antrodia favescens, related to the medicinal Antrodia cinnamomea, was identified in another location, known for its role in Chinese herbal medicine against cancer and metabolic diseases. Ochrocladosporium elatum, recognized for its antioxidant and antibacterial activities, was found elsewhere. Additionally, natural wines exhibited greater bacterial biodiversity, contributing to unique tastes and potential health benefits.

Global dissemination of the beta-lactam resistance gene blaTEM-1 among pathogenic bacteria

Antibiotic resistance presents a burgeoning global health crisis, with over 70 % of pathogenic bacteria now exhibiting resistance to at least one antibiotic. This study leverages a vast dataset of 618,853 pathogenic bacterial genomes from the NCBI pathogen detection database, offering comprehensive insights into antibiotic resistance patterns, species-specific profiles, and transmission dynamics of resistant pathogens. We centered our investigation on the beta-lactam resistance gene blaTEM-1, found in 43,339 genomes, revealing its extensive distribution across diverse species and isolation sources. The study unveiled the prevalence of 15 prominent antibiotic resistance genes (ARGs), including those conferring resistance to beta-lactam, aminoglycoside, and tetracycline antibiotics. Distinct resistance patterns were observed between Gram-positive and Gram-negative bacteria, indicating the influence of phylogeny on resistance dissemination. Notably, the blaTEM-1 gene demonstrated substantial prevalence across a wide array of bacterial species (8) and a high number of isolation sources (11). Genetic context analysis revealed associations between blaTEM-1 and mobile genetic elements (MGEs) like transposons and insertion sequences. Additionally, we observed recent horizontal transfer events involving clusters of blaTEM-1 genes and MGEs underscore the potential of MGEs in facilitating the mobilization of ARGs. Our findings underscore the importance of adopting a One Health approach to global genomic pathogen surveillance, aiming to uncover the transmission routes of ARGs and formulate strategies to address the escalating antibiotic resistance crisis.

Antimicrobial-resistant genes in feces from otters (Lontra longicaudis) within the Peñas Blancas river basin, Costa Rica

Antimicrobial resistance poses a growing threat to human health, yet its implications for wildlife remain a subject of ongoing research. River otters inhabiting the Peñas Blancas River face exposure to various anthropogenic activities in their habitat, potentially leading to the accumulation of antibiotic-resistant genes (ARGs) with unknown consequences for their health. This study aimed to identify specific ARGs in otter feces from this river basin, employing quantitative polymerase chain reaction (qPCR), DNA sequencing of ARGs, and phylogenetic analysis techniques. Over the period from 2019 to 2022, we collected 102 fecal samples from otters through the Peñas Blancas River watershed, spanning its upper and middle basins. We assessed the bacterial presence via the 16S rRNA gene through qPCR analysis and screened for 12 ARGs. Sequences of 16 ARG-positive samples were subsequently analyzed using Maximum-likelihood-base taxonomic placement. In total, 56 samples tested positive for the 16S rRNA gene, with 24 exhibiting at least one ARG. Notably, three samples showcased a "multi-resistance microbiome". qPCR analyses identified seven distinct ARGs: tetB (in 26.8 % of the samples), sulI (21.4 %), sulII (21.4 %), qnrS (10.7 %), tetQ (8.9 %), tetW (7.1 %), and tetA (3.6 %). Phylogenetic analysis confirmed the taxonomic association of all detected ARGs, which were compared with The Comprehensive Antibiotic Resistance Database. Our findings underscore the importance of comprehending the spread of ARGs in wildlife populations, with river otters serving as potential sentinels for ARG dissemination. Moreover, they highlight the potential impact of anthropogenic activities on the health of aquatic ecosystems, emphasizing the need for proactive measures to mitigate antimicrobial resistance in natural environments.

Antibiotic Resistance in Fermented Foods Chain: Evaluating the Risks of Emergence of Enterococci as an Emerging Pathogen in Raw Milk Cheese

Fermented foods, particularly fermented dairy products, offer significant health benefits but also present serious concerns. Probiotic bacteria, such as lactic acid bacteria (LAB), found in these foods have been strongly linked to the selection and dissemination of antibiotic resistance genes (ARGs). This study aims to examine the potential risks associated with fermented foods, despite their importance in human nutrition, by analyzing the entire production chain from raw material acquisition to storage. Focusing on cheese production as a key fermented food, the study will investigate various aspects, including dairy farm management, milk acquisition, milk handling, and the application of good manufacturing practices (GMP) and good hygiene practices (GHP) in cheese production. The findings of this review highlight that ARGs found in LAB are similar to those observed in hygiene indicator bacteria like E. coli and pathogens like S. aureus. The deliberate use of antibiotics in dairy farms and the incorrect use of disinfectants in cheese factories contribute to the prevalence of antibiotic-resistant bacteria in cheeses. Cheese factories, with their high frequency of horizontal gene transfer, are environments where the microbiological diversity of raw milk can enhance ARG transfer. The interaction between the raw milk microbiota and other environmental microbiotas, facilitated by cross-contamination, increases metabolic communication between bacteria, further promoting ARG transfer. Understanding these bacterial and ARG interactions is crucial to ensure food safety for consumers.

Prevalence of Antibiotic Resistance Genes in Differently Processed Smoothies and Fresh Produce from Austria

Plant-derived foods are potential vehicles for microbial antibiotic resistance genes (ARGs), which can be transferred to the human microbiome if consumed raw or minimally processed. The aim of this study was to determine the prevalence and the amount of clinically relevant ARGs and mobile genetic elements (MGEs) in differently processed smoothies (freshly prepared, cold-pressed, pasteurized and high-pressure processed) and fresh produce samples (organically and conventionally cultivated) to assess potential health hazards associated with their consumption. The MGE ISPps and the class 1 integron-integrase gene intI1 were detected by probe-based qPCR in concentrations up to 104 copies/mL in all smoothies, lettuce, carrots and a single tomato sample. The highest total (2.2 × 105 copies/mL) and the most diverse ARG and MGE loads (16/26 targets) were observed in freshly prepared and the lowest prevalences (5/26) and concentrations (4.1 × 103 copies/mL) in high-pressure-processed (HPP) smoothies. BlaCTX-M-1-15 (1.2 × 105 c/mL) and strB (6.3 × 104 c/mL) were the most abundant, and qacEΔ1 (95%), blaTEM1 (85%), ermB and sul1 (75%, each) were the most prevalent ARGs. QnrS, vanA, sat-4, blaKPC, blaNDM-1 and blaOXA-10 were never detected. HPP treatment reduced the microbial loads by ca. 5 logs, also destroying extracellular DNA potentially encoding ARGs that could otherwise be transferred by bacterial transformation. The bacterial microbiome, potential pathogens, bacterial ARG carriers and competent bacteria able to take up ARGs were identified by Illumina 16S rRNA gene sequencing. To reduce the risk of AMR spread from smoothies, our data endorse the application of DNA-disintegrating processing techniques such as HPP.

Oropharyngeal resistome remains stable during COVID-19 therapy, while fecal resistome shifts toward a less diverse resistotype

Antimicrobial resistance poses a serious threat to global public health. The COVID-19 pandemic underscored the need to monitor the dissemination of antimicrobial resistance genes and understand the mechanisms driving this process. In this study, we analyzed changes to the oropharyngeal and fecal resistomes of patients with COVID-19 undergoing therapy in a hospital setting. A targeted sequencing panel of 4,937 resistance genes was used to comprehensively characterize resistomes. Our results demonstrated that the oropharyngeal resistome is homogeneous, showing low variability over time. In contrast, fecal samples clustered into two distinct resistotypes that were only partially related to enterotypes. Approximately half of the patients changed their resistotype within a week of therapy, with the majority transitioning to a less diverse and ermB-dominated resistotype 2. Common macrolide resistance genes were identified in over 80% of both oropharyngeal and fecal samples, likely originating from streptococci. Our findings suggest that the fecal resistome is a dynamic system that can exist in certain "states" and is capable of transitioning from one state to another. To date, this is the first study to comprehensively describe the oropharyngeal resistome and its variability over time, and one of the first studies to demonstrate the temporal dynamics of the fecal resistotypes.

Antimicrobial resistance in plant endophytes associated with poultry-manure application revealed by selective culture and whole genome sequencing

Poultry manure is widely used as organic fertilizer in agriculture during the cultivation of crops, but the persistent high-level use of antibiotics in poultry production has raised concerns about the selection for reservoirs of antimicrobial resistance genes (ARGs). Previous studies have shown that the addition of poultry manure can increase the abundance of genes associated with resistance to tetracyclines, aminoglycosides, fluoroquinolones, sulfonamides, bacitracin, chloramphenicol, and macrolide-lincosamide-streptogramin in soil and plants. Understanding the microbial populations that harbor these ARGs is important to identify microorganisms that could enter the human food chain. Here, we test the hypothesis that environmental exposure to poultry manure increases the occurrence of antimicrobial resistance (AMR) in plant endophytes using selective culture, phenotypic Antibiotic Susceptibility Testing (AST), phylogenetic analysis, and whole genome sequencing (WGS). Endophytes from poultry manure treated Sorghum bicolor (L.) Moench plant root and stem samples showed increased phenotypic and genotypic resistance against multiple antibiotics compared to untreated controls. Comparison of AMR phenotype-to-genotype relationships highlighted the detection of multi-drug resistant (MDR) plant endophytes, demonstrating the value of genomic surveillance for emerging drug-resistant pathogens. The increased occurrence of ARGs in poultry manure-exposed endophytes highlights the need for responsible antibiotic use in poultry and animal farming to reduce contamination of ecological niches and transgression into endophytic plant microbiome compartments. It also emphasizes the requirement for proper manure management practices and vigilance in monitoring and surveillance efforts to tackle the growing problem of antibiotic resistance and preserve the efficacy of antibiotics for human and veterinary medicine.

Transfer dynamics of antimicrobial resistance among gram-negative bacteria

Antimicrobial resistance (AMR) in gram-negative bacteria (GNBs) is a significant global health concern, exacerbated by mobile genetic elements (MGEs). This review examines the transfer of antibiotic resistance genes (ARGs) within and between different species of GNB facilitated by MGEs, focusing on the roles of plasmids and phages. The impact of non-antibiotic chemicals, environmental factors affecting ARG transfer frequency, and underlying molecular mechanisms of bacterial resistance evolution are also discussed. Additionally, the study critically assesses the impact of fitness costs and compensatory evolution driven by MGEs in host organisms, shedding light on the transfer frequency of ARGs and host evolution within ecosystems. Overall, this comprehensive review highlights the factors and mechanisms influencing ARG movement among diverse GNB species and underscores the importance of implementing holistic One-Health strategies to effectively address the escalating public health challenges associated with AMR.

Tetracycline resistance gene transfer from Escherichia coli donors to Salmonella Heidelberg in chickens is impacted by the genetic context of donors

Chicken ceca are a rich source of bacteria, including zoonotic pathogens such as Salmonella enterica. The microbiota includes strains/species carrying antimicrobial resistance genes and horizontal transfer of resistance determinants between species may increase the risk to public health and farming systems. Possible sources of these antimicrobial resistance donors - the eggshell carrying bacteria from the hen vertically transmitted to the offspring, or the barn environment where chicks are hatched and raised - has been little explored. In this study, we used Salmonella enterica serovar Heidelberg to evaluate if layer chicks raised in different environments (using combinations of sterilized or non-sterile eggs placed in sterilized isolation chambers or non-sterile rooms) acquired transferable tetracycline resistance genes from surrounding bacteria, especially Escherichia coli. Two-day old chicks were challenged with an antibiotic-susceptible S. Heidelberg strain SH2813nalR and Salmonella recovered from the cecum of birds at different timepoints to test the in vivo acquisition of tetracycline resistance. Tetracycline-resistant E. coli isolates recovered from birds from the in vivo experiment were used to test the in vitro transfer of tetracycline resistance genes from E. coli to Salmonella. Even though Salmonella SH2813nalR colonized the 2-day old chicks after oral challenge, tetracycline-resistant Salmonella transconjugants were not recovered, as previously observed. In vitro experiments provided similar results. We discuss several hypotheses that might explain the absence of transconjugants in vitro and in vivo, despite the presence of diverse plasmids in the recovered E. coli. The factors that can inhibit/promote antimicrobial resistance transfers to Salmonella for different plasmid types need further exploration.

Research on antibiotic resistance genes in wild and artificially bred green turtles (Chelonia mydas)

Sea turtles, vital to marine ecosystems, face population decline. Artificial breeding is a recovery strategy, yet it risks introducing antibiotic resistance genes (ARGs) to wild populations and ecosystems. This study employed metagenomic techniques to compare the distribution characteristics of ARGs in the guts of wild and artificially bred green turtles (Chelonia mydas). The findings revealed that the total abundance of ARGs in C. mydas that have been artificially bred was significantly higher than that in wild individuals. Additionally, the abundance of mobile genetic elements (MGEs) co-occurring with ARGs in artificially bred C. mydas was significantly higher than in wild C. mydas. In the analysis of bacteria carrying ARGs, wild C. mydas exhibited greater bacterial diversity. Furthermore, in artificially bred C. mydas, we discovered 23 potential human pathogenic bacteria (HPB) that contain antibiotic resistance genes. In contrast, in wild C. mydas, only one type of HPB carrying an antibiotic resistance gene was found. The findings of this study not only enhance our understanding of the distribution and dissemination of ARGs within the gut microbial communities of C. mydas, but also provide vital information for assessing the potential impact of releasing artificially bred C. mydas on the spread of antibiotic resistance.

Metagenomic insights into resistome, mobilome and virulome in different fecal waste

Fecal waste is a significant source of antimicrobial resistance (AMR) pollution and provides valuable insights into the AMR development in animal and human populations within the "One health" framework. Various genetic elements, including antibiotic resistance genes (ARGs), biocide and metal resistance genes (BMGs), mobile genetic elements (MGEs), and virulence factor genes (VFGs), are crucial AMR risk determinants (ARDs). However, few studies focused on compositional characteristics of ARDs in different feces. Here, we analyzed 753 public metagenomes from human, pig, chicken, and cattle feces, revealing significant differences in ARD richness and abundance across fecal types, notably lowest in cattle samples. Tetracycline, multi-metal, and -biocide resistance genes were dominant resistome. A few core genes contributed to 25.6%-91.1% of gene abundance, and their correlations were stronger in cattle samples. Procrustes analysis showed that microbial composition had higher correlations with ARGs (M2 = 0.579) and BMGs (M2 = 0.519). Gammaproteobacteria was identified as major ARD-hosts especially in human and pig feces, and they mainly carried multi-resistance genes. MGEs exhibited direct positive effects on ARGs and BMGs, indirectly impacting VFGs. Utilizing random forest methods, we identified 42 indicator genes for tracking AMR pollution originating from fecal sources in the environments. This study offers new insights into understanding and controlling the AMR pollution of fecal waste from human and food animals.

Effects of sulfamethazine and tetracycline at molecular, cellular and tissue levels in Eisenia fetida earthworms

Soil contamination by antibiotics is a global issue of great concern that contributes to the rise of bacterial antibiotic resistance and can have toxic effects on non-target organisms. This study evaluated the variations of molecular, cellular, and histological parameters in Eisenia fetida earthworms exposed to sulfamethazine (SMZ) and tetracycline (TC), two antibiotics commonly found in agricultural soils. The earthworms were exposed for 14 days to a series of concentrations (0, 10, 100, and 1000 mg/kg) of both antibiotics. SMZ and TC did not affect the survival of E. fetida, however, other effects at different levels of biological complexity were detected. The two highest concentrations of SMZ reduced the viability of coelomocytes. At the highest TC concentration, there was a noticeable decline in cell viability, acetylcholinesterase activity (neurotoxicity), and the relative presence of mucopolysaccharides in the epidermis (mucous production). Glutathione S-transferase activity decreased in all TC treatments and at the highest SMZ concentration. However, levels of malondialdehyde and protein carbonyls did not change, suggesting an absence of oxidative stress. Tetracycline was neurotoxic to E. fetida and changed the integrity of the epidermis. Both antibiotics altered the intestinal microbiota of E. fetida, leading to a reduction in the relative abundance of bacteria from the phyla Proteobacteria and Bacteroidetes, while causing an increase in the phylum Actinobacteroidota. All observed changes indicate that both SMZ and TC can disrupt the earthworms' immune system and gut microbiome, while fostering the growth of bacteria that harbour antibiotic resistance genes. Finally, both antibiotics exerted additional metabolic and physiological effects that increased the vulnerability of E. fetida to pathogens.

Investigating the changing taxonomy and antimicrobial resistance of bacteria isolated from door handles in a new infectious disease ward pre- and post-patient admittance

Healthcare-associated infections (HAIs) are a significant burden to health systems, with antimicrobial resistance (AMR) further compounding the issue. The hospital environment plays a significant role in the development of HAIs, with microbial surveillance providing the foundation for interventions. We sampled 40 door handles at a newly built hospital prior to patients being admitted and then 6 and 12 months after this date. We utilized 16S rDNA sequencing to identify unique colonies, disc diffusion assays to assess the antibiotic resistance of Staphylococcus spp., and whole-genome sequenced (WGS) multidrug-resistant (MDR) isolates. Before patient admission, 43% of sites harbored Staphylococcus spp., increasing to 55% and 65% at six and 12 months, respectively, while Bacillus spp. saw a large increase from 3% to 68% and 85%, respectively. No ESKAPE pathogens were identified. Staphylococcus spp. showed relatively low resistance to all antibiotics except cefoxitin (56%) before patient admittance. Resistance was highest after 6 months of ward use, with an increase in isolates susceptible to all antibiotics after 12 months (11% and 54% susceptibility, respectively). However, MDR remained high. WGS revealed blaZ (25/26), and mecA (22/26) and aac6-aph2 (20/26) were the most abundant resistance genes. Two Staphylococcus hominis isolates identified at the first two time points, respectively, and three Staphylococcus epidermidis isolates identified at all three time points, respectively, were believed to be clonal. This study highlighted the prevalence of a resistant reservoir of bacteria recoverable on high-touch surfaces and the long-term persistence of Staphylococcus spp. first introduced prior to patient admission.

IMPORTANCE

Healthcare-associated infections (HAIs) are a significant burden to health systems, conferring increased morbidity, mortality, and financial costs to hospital admission. Antimicrobial resistance (AMR) further compounds the issue as viable treatment options are constrained. Previous studies have shown that environmental cleaning interventions reduced HAIs. To ensure the effectiveness of these, it is important to analyze the hospital environment at a microbial level, particularly high-touch surfaces which see frequent human interaction. In addition to identifying infectious microorganisms, it is also beneficial to assess typically non-infectious organisms, as traits including AMR can be transferred between the two. Our study identified that there were high levels of antibiotic resistance in typically non-infectious organisms found on high touch surfaces on a hospital ward. However, the organisms identified suggested that the cleaning protocols in place were sufficient, with their presence being due to repeated recolonization events through human interaction after cleaning had taken place.

Data-Driven Approaches in Antimicrobial Resistance: Machine Learning Solutions

Background/Objectives: The emergence of antimicrobial resistance (AMR) due to the misuse and overuse of antibiotics has become a critical threat to global public health. There is a dire need to forecast AMR to understand the underlying mechanisms of resistance for the development of effective interventions. This paper explores the capability of machine learning (ML) methods, particularly unsupervised learning methods, to enhance the understanding and prediction of AMR. It aims to determine the patterns from AMR gene data that are clinically relevant and, in public health, capable of informing strategies. Methods: We analyzed AMR gene data in the PanRes dataset by applying unsupervised learning techniques, namely K-means clustering and Principal Component Analysis (PCA). These techniques were applied to identify clusters based on gene length and distribution according to resistance class, offering insights into the resistance genes' structural and functional properties. Data preprocessing, such as filtering and normalization, was conducted prior to applying machine learning methods to ensure consistency and accuracy. Our methodology included the preprocessing of data and reduction of dimensionality to ensure that our models were both accurate and interpretable. Results: The unsupervised learning models highlighted distinct clusters of AMR genes, with significant patterns in gene length, including their associated resistance classes. Further dimensionality reduction by PCA allows for clearer visualizations of relationships among gene groupings. These patterns provide novel insights into the potential mechanisms of resistance, particularly the role of gene length in different resistance pathways. Conclusions: This study demonstrates the potential of ML, specifically unsupervised approaches, to enhance the understanding of AMR. The identified patterns in resistance genes could support clinical decision-making and inform public health interventions. However, challenges remain, particularly in integrating genomic data and ensuring model interpretability. Further research is needed to advance ML applications in AMR prediction and management.

Hydroxyl radicals dominated the reduction of antibiotic resistance genes by inactivating Gram-negative bacteria during soil electrokinetic treatment

Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are emerging contaminants that widely exist in the environment. Effective reduction of ARB and ARGs from soil and water could be achieved by electrokinetic remediation (EKR) technology. In water, hydroxyl radicals (·OH) are proved to play a major role in the EKR process; while the reduction mechanism of ARB and ARGs is still unclear in soil. In this study, different concentrations of hydroxyl radical scavengers (salicylic acid) were added to the EKR system to explore the possible role of ·OH in the reduction of ARB and ARGs. The results showed that generally, ·OH played a more vital role in the reduction of ARB (65.24-72.46%) compared to the reduction of total cultivable bacteria (57.50%). And ·OH contributed to a higher reduction of sul genes (60.94%) compared to tet genes (47.71%) and integrons (36.02%). It was found that the abundance of Gram-negative bacteria (Chloroflexi, Acidobacteria and norank_c_Acidobacteria) was significantly reduced, and the correlation between norank_f_Gemmatimonadaceae and sul1 was weakened in the presence of ·OH. Correlation analysis indicated that the abundance of ARGs (especially sul1) was closely related to the Gram-negative bacteria (Proteobacteria, Acidobacteria, and Gemmatimonadetes) in the soil EKR treatment. Moreover, changes in bacterial community structure affected the abundance of ARB and ARGs indirectly. Overall, this study revealed the reduction mechanism of ARB and ARGs by ·OH in the soil EKR system for the first time. These findings provide valuable support for soil remediation efforts focusing on controlling antibiotic resistance.

Metagenomic profiling of cecal microbiota and antibiotic resistome in rodents

The rodent gut microbiota is a known reservoir of antimicrobial resistance, yet the distribution of antibiotic resistance genes (ARGs) within rodent cecal microbial communities and the specific bacterial species harboring these ARGs remain largely underexplored. This study employed high-throughput sequencing of 122 samples from five distinct rodent species to comprehensively profile the diversity and distribution of ARGs and to identify the bacterial hosts of these genes. A gene catalog of the rodent cecal microbiome was constructed, comprising 22,757,369 non-redundant genes. Analysis of the microbial composition and diversity revealed that Bacillota and Bacteroidota were the dominant bacterial phyla across different rodent species, with significant variations in species composition among the rodents. In total, 3703 putative antimicrobial resistance protein-coding genes were identified, corresponding to 392 unique ARG types classified into 32 resistance classes. The most enriched ARGs in the rodent cecal microbiome were associated with multidrug resistance, followed by glycopeptide and elfamycin antibiotics. Procrustes analysis demonstrated a correlation between the structure of the microbial community and the resistome. Metagenomic assembly-based host tracking indicated that most ARG-carrying contigs originated from the bacterial family Oscillospiraceae. Additionally, 130 ARGs showed significant correlations with mobile genetic elements. These findings provide new insights into the cecal microbiota and the prevalence of ARGs across five rodent species. Future research on a wider range of wild rodent species carrying ARGs will further elucidate the mechanisms underlying the transmission of antimicrobial resistance.

Modulation of fecal microbiota and reductions in fecal antibiotic resistance genes (ARGs) driven by Weissella-fermented feed in growing pigs

Probiotics-induced feed fermentation can improve the composition of microbiota, leading to benefits in pig production. However, the influence of probiotics-driven feed fermentation on pollution reduction is limited. This study aimed to analyze the impact of Weissella-based feed fermentation on the chemical characteristics, changes in microbial abundance, and antibiotic resistance genes (ARGs). Moreover, the possible mechanism and the association among them was also analyzed. First, pigs reared on fermented feed exhibited improved growth performance. The fermentation group showed a significant reduction in emissions of total phosphorus (TP), total carbon (TC), organic matter (OM), copper (Cu), and zinc (Zn) levels in feces compared to the control group. The fermentation group also showed a significant decrease in the ARGs, especially for the tetX, tetW, tetQ, tetL, tetO, tet32, tet44, ermG, ermF, CfxA2, CfxA3, aph3-III, aadA, and ant9-I, compared to the control group. The primary functional microbiota, characterized by increased levels of Bifidobacterium, Megasphaera, and Mitsuokella, and decreased levels of Methanosphaera, and Ruminiclostridium, displayed both negative and positive correlations with ARGs, TC, TP, OM, Cu, and Zn. Furthermore, a significant association was observed between the alterations in microbiota and ARGs and the lactic acid concentration in the fermented feed. The molecular docking results showed a good fit between lactate dehydrogenase and three antibiotics, particularly tetracycline. In conclusion, these results offer novel targets and strategies to address environmental pollutants associated with pig farming.

Metagenomics reveals the potential transmission risk of resistomes from urban park environment to human

Urban parks play a significant role in urban ecosystems and are strongly associated with human health. Nevertheless, the biological contamination of urban parks - opportunistic pathogens and antibiotic resistance genes (ARGs) - has been poorly reported. Here, metagenomic and 16 S rRNA sequencing methods were used to study the distribution and assembly of opportunistic pathogens and ARGs in soil and water from nine parks in Lanzhou city, and further compared them with local human gut microbiomes to investigate the potential transmission risk. Our results revealed that the most important type of drug resistance in urban parks was multidrug resistance, with various resistance mechanisms. Approximately half of ARGs were shared between human gut and park environment, and it was noteworthy that cross-species transmission might exist among some high-risk ARGs, such as mepA and mdtE, with a significant enrichment in human gut. Metagenomic binning uncovered several bacterial genomes carrying adjacent ARGs, MGEs, and virulence genes, indicating a possibility that these genes may jointly transfer among different environments, particularly from park environment to human. Our results provided a reference point for the management of environmental pollutants in urban parks.

Molecular characterization and antibiotic resistance of Staphylococcus aureus strains isolated from patients with diarrhea in Korea between the years 2007 and 2022

To investigate the molecular characteristics and antibiotic resistance of Staphylococcus aureus isolates from patients with diarrhea in Korea, 327 S. aureus strains were collected between 2007 and 2022. The presence of staphylococcal enterotoxin (SE) and toxic shock syndrome toxin-1 (TSST-1) genes in S. aureus isolates was determined by PCR. The highest expression of the TSST-1 gene was found in the GIMNO type (43.1% of GIMNO type). GIMNO type (Type I) refers to each staphylococcal enterotoxin (SE) gene gene (initials of genes): G = seg; I = sei; M = selm; N = seln; O = selo. Moreover, Type I isolates showed a significantly higher resistance to most antibiotics. A total of 195 GIMNO-type S. aureus strains were analyzed using multilocus sequence typing (MLST), and 18 unique sequence types (STs) were identified. The most frequent sequence type was ST72 (36.9%), followed by ST5 (22.1%) and ST30 (16.9%). Interestingly, ST72 strains showed a higher prevalence of MRSA than the other STs. In conclusion, our results were the first reported for S. aureus strains in Korea, which significantly expanded S. aureus genotype information for the surveillance of pathogenic S. aureus and may provide important epidemiological information to resolve several infectious diseases caused by S. aureus.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01478-9.

The impact of antibiotic exposure on antibiotic resistance gene dynamics in the gut microbiota of inflammatory bowel disease patients

Background

While antibiotics are commonly used to treat inflammatory bowel disease (IBD), their widespread application can disturb the gut microbiota and foster the emergence and spread of antibiotic resistance. However, the dynamic changes to the human gut microbiota and direction of resistance gene transmission under antibiotic effects have not been clearly elucidated.

Methods

Based on the Human Microbiome Project, a total of 90 fecal samples were collected from 30 IBD patients before, during and after antibiotic treatment. Through the analysis workflow of metagenomics, we described the dynamic process of changes in bacterial communities and resistance genes pre-treatment, during and post-treatment. We explored potential consistent relationships between gut microbiota and resistance genes, and established gene transmission networks among species before and after antibiotic use.

Results

Exposure to antibiotics can induce alterations in the composition of the gut microbiota in IBD patients, particularly a reduction in probiotics, which gradually recovers to a new steady state after cessation of antibiotics. Network analyses revealed intra-phylum transfers of resistance genes, predominantly between taxonomically close organisms. Specific resistance genes showed increased prevalence and inter-species mobility after antibiotic cessation.

Conclusion

This study demonstrates that antibiotics shape the gut resistome through selective enrichment and promotion of horizontal gene transfer. The findings provide insights into ecological processes governing resistance gene dynamics and dissemination upon antibiotic perturbation of the microbiota. Optimizing antibiotic usage may help limit unintended consequences like increased resistance in gut bacteria during IBD management.

Infant age inversely correlates with gut carriage of resistance genes, reflecting modifications in microbial carbohydrate metabolism during early life

The infant gut microbiome is increasingly recognized as a reservoir of antibiotic resistance genes, yet the assembly of gut resistome in infants and its influencing factors remain largely unknown. We characterized resistome in 4132 metagenomes from 963 infants in six countries and 4285 resistance genes were observed. The inherent resistome pattern of healthy infants (N = 272) could be distinguished by two stages: a multicompound resistance phase (Months 0-7) and a tetracycline-mupirocin-β-lactam-dominant phase (Months 8-14). Microbial taxonomy explained 40.7% of the gut resistome of healthy infants, with Escherichia (25.5%) harboring the most resistance genes. In a further analysis with all available infants (N = 963), we found age was the strongest influencer on the resistome and was negatively correlated with the overall resistance during the first 3 years (p < 0.001). Using a random-forest approach, a set of 34 resistance genes could be used to predict age (R 2 = 68.0%). Leveraging microbial host inference analyses, we inferred the age-dependent assembly of infant resistome was a result of shifts in the gut microbiome, primarily driven by changes in taxa that disproportionately harbor resistance genes across taxa (e.g., Escherichia coli more frequently harbored resistance genes than other taxa). We performed metagenomic functional profiling and metagenomic assembled genome analyses whose results indicate that the development of gut resistome was driven by changes in microbial carbohydrate metabolism, with an increasing need for carbohydrate-active enzymes from Bacteroidota and a decreasing need for Pseudomonadota during infancy. Importantly, we observed increased acquired resistance genes over time, which was related to increased horizontal gene transfer in the developing infant gut microbiome. In summary, infant age was negatively correlated with antimicrobial resistance gene levels, reflecting a composition shift in the gut microbiome, likely driven by the changing need for microbial carbohydrate metabolism during early life.

The multi-kingdom microbiome catalog of the chicken gastrointestinal tract

Chicken is an important food animal worldwide and plays an important role in human life by providing meat and eggs. Despite recent significant advances in gut microbiome studies, a comprehensive study of chicken gut bacterial, archaeal, and viral genomes remains unavailable. In this study, we constructed a chicken multi-kingdom microbiome catalog (CMKMC), including 18,201 bacterial, 225 archaeal, and 33,411 viral genomes, and annotated over 6,076,006 protein-coding genes by integrating 135 chicken gut metagenomes and publicly available metagenome-assembled genomes (MAGs) from ten countries. We found that 812 and 240 MAGs in our dataset were putative novel species and genera, respectively, far beyond what was previously reported. The newly unclassified MAGs were predominant in Phyla Firmicutes_A (n = 263), followed by Firmicutes (n = 126), Bacteroidota (n = 121), and Proteobacteria (n = 87). Most of the classified species-level viral operational taxonomic units belong to Caudovirales. Approximately, 63.24 % of chicken gut viromes are predicted to infect two or more hosts, including complete circular viruses. Moreover, we found that diverse auxiliary metabolic genes and antibiotic resistance genes were carried by viruses. Together, our CMKMC provides the largest integrated MAGs and viral genomes from the chicken gut to date, functional insights into the chicken gastrointestinal tract microbiota, and paves the way for microbial interventions for better chicken health and productivity.

[Tracking transfers of resistance-carrying bacteria between animals, humans and the environment]

The fight against antibiotic resistance must incorporate the "One Health" concept to be effective. This means having a holistic approach embracing the different ecosystems, human, animal, and environment. Transfers of resistance genes may exist between these three domains and different stresses related to the exposome may influence these transfers. Various targeted or pan-genomic molecular biology techniques can be used to better characterise the dissemination of bacterial clones and to identify exchanges of genes and mobile genetic elements between ecosystems.

Antibiotics soil-solution chemistry: A review of environmental behavior and uptake and transformation by plants

The increased use of antibiotics by humans for various purposes has left the environment polluted. Antibiotic pollution remediation is challenging because antibiotics exist in trace amounts and only highly sensitive detection techniques could be used to quantify them. Nevertheless, their trace quantity is not a hindrance to their transfer along the food chain, causing sensitization and the development of antibiotic resistance. Despite an increase in the literature on antibiotic pollution and the development and transfer of antibiotic-resistant genes (ARGs), little attention has been given to the behavior of antibiotics at the soil-solution interface and how this affects antibiotic adsorption-desorption interactions and subsequent uptake and transformation by plants. Thus, this review critically examines the interactions and possible degradation mechanisms of antibiotics in soil and the link between antibiotic soil-solution chemistry and uptake by plants. Also, different factors influencing antibiotic mobility in soil and the transfer of ARGs from one organism to another were considered. The mechanistic and critical analyses revealed that: (a) the charge characteristics of antibiotics at the soil-root interface determine whether they are adsorbed to soil or taken up by plants; (b) antibiotics that avoid soil colloids and reach soil pore water can be absorbed by plant roots, but their translocation to the stem and leaves depends on the ionic state of the molecule; (c) few studies have explored how plants adapt to antibiotic pollution and the transformation of antibiotics in plants; and (d) the persistence of antibiotics in cropland soils can be influenced by the content of soil organic matter, coexisting ions, and fertilization practices. Future research should focus on the soil/solution-antibiotic-plant interactions to reveal detailed mechanisms of antibiotic transformation by plants and whether plant-transformed antibiotics could be of environmental risk.

Dissemination of antibiotic resistance genes is regulated by iron oxides: Insight into the influence on bacterial transformation

The transportation of antibiotic resistance genes (ARGs) in manure-soil-plant continuums poses risks to human health. Horizontal gene transfer, particularly for bacterial transformation, is an important way for ARG dissemination. As crucial components in soils, iron oxides impacted the fates of various abiotic and biotic contaminants due to their active properties. However, whether they can influence the transformation of ARGs is unknown, which waits to be figured out to boost the assessment and control of ARG spread risks. In this study, we have investigated the effects of goethite, hematite, and magnetite (0-250 mg/L, with sizes < 100 nm and > 100 nm) on the transfer of ampicillin resistance genes to Escherichia coli cells. At lower iron oxide concentrations, the transformation of ARGs was first facilitated (transformation frequency reached up to 3.38-fold higher), but the facilitating effects gradually weakened and eventually disappeared as concentrations further increased. Particle size and iron oxide type were not the universal determinants controlling the transformation. At lower concentrations, iron oxides interacted with proteins and phospholipids in E. coli envelope structures, and induced the overgeneration of intracellular reactive oxygen species. Consequently, they led to pore formation and permeability enhancement on the cell membrane, thus promoting the transformation. The facilitation was also associated with the carrier-like effect of iron oxides for antibiotic resistance plasmids. At higher concentrations, the weakened facilitations were attributed to the aggregation of iron oxides. In this study, we highlight the crucial roles of the concentrations (contents) of iron oxides on the dissemination of ARGs in soils; this study may serve as a reference for ARG pollution control in future agricultural production.

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.

Unraveling the diversity and dissemination dynamics of antimicrobial resistance genes in Enterobacteriaceae plasmids across diverse ecosystems

AIM

The objective of this study was to investigate the antimicrobial resistance genes (ARGs) in plasmids of Enterobacteriaceae from soil, sewage, and feces of food-producing animals and humans.

METHODS AND RESULTS

The plasmid sequences were obtained from the NCBI database. For the identification of ARG, comprehensive antibiotic resistance database (CARD), and ResFinder were used. Gene conservation and evolution were investigated using DnaSP v.6. The transfer potential of the plasmids was evaluated using oriTfinder and a MOB-based phylogenetic tree was reconstructed using Fastree. We identified a total of 1064 ARGs in all plasmids analyzed, conferring resistance to 15 groups of antibiotics, mostly aminoglycosides, beta-lactams, and sulfonamides. The greatest number of ARGs per plasmid was found in enterobacteria from chicken feces. Plasmids from Escherichia coli carrying multiple ARGs were found in all ecosystems. Some of the most abundant genes were shared among all ecosystems, including aph(6)-Id, aph(3'')-Ib, tet(A), and sul2. A high level of sequence conservation was found among these genes, and tet(A) and sul2 are under positive selective pressure. Approximately 62% of the plasmids carrying at least one ARG were potentially transferable. Phylogenetic analysis indicated a potential co-evolution of Enterobacteriaceae plasmids in nature.

CONCLUSION

The high abundance of Enterobacteriaceae plasmids from diverse ecosystems carrying ARGs reveals their widespread distribution and importance.

Metagenomics reveals the temporal dynamics of the rumen resistome and microbiome in goat kids

BACKGROUND

The gut microbiome of domestic animals carries antibiotic resistance genes (ARGs) which can be transmitted to the environment and humans, resulting in challenges of antibiotic resistance. Although it has been reported that the rumen microbiome of ruminants may be a reservoir of ARGs, the factors affecting the temporal dynamics of the rumen resistome are still unclear. Here, we collected rumen content samples of goats at 1, 7, 14, 28, 42, 56, 70, and 84 days of age, analyzed their microbiome and resistome profiles using metagenomics, and assessed the temporal dynamics of the rumen resistome in goats at the early stage of life under a conventional feeding system.

RESULTS

In our results, the rumen resistome of goat kids contained ARGs to 41 classes, and the richness of ARGs decreased with age. Four antibiotic compound types of ARGs, including drugs, biocides, metals, and multi-compounds, were found during milk feeding, while only drug types of ARGs were observed after supplementation with starter feed. The specific ARGs for each age and their temporal dynamics were characterized, and the network inference model revealed that the interactions among ARGs were related to age. A strong correlation between the profiles of rumen resistome and microbiome was found using Procrustes analysis. Ruminal Escherichia coli within Proteobacteria phylum was the main carrier of ARGs in goats consuming colostrum, while Prevotella ruminicola and Fibrobacter succinogenes associated with cellulose degradation were the carriers of ARGs after starter supplementation. Milk consumption was likely a source of rumen ARGs, and the changes in the rumen resistome with age were correlated with the microbiome modulation by starter supplementation.

CONCLUSIONS

Our data revealed that the temporal dynamics of the rumen resistome are associated with the microbiome, and the reservoir of ARGs in the rumen during early life is likely related to age and diet. It may be a feasible strategy to reduce the rumen and its downstream dissemination of ARGs in ruminants through early-life dietary intervention. Video Abstract.

Innovative Biomedical and Technological Strategies for the Control of Bacterial Growth and Infections

Antibiotics comprise one of the most successful groups of pharmaceutical products. Still, they have been associated with developing bacterial resistance, which has become one of the most severe problems threatening human health today. This context has prompted the development of new antibiotics or co-treatments using innovative tools to reverse the resistance context, combat infections, and offer promising antibacterial therapy. For the development of new alternatives, strategies, and/or antibiotics for controlling bacterial growth, it is necessary to know the target bacteria, their classification, morphological characteristics, the antibiotics currently used for therapies, and their respective mechanisms of action. In this regard, genomics, through the sequencing of bacterial genomes, has generated information on diverse genetic resources, aiding in the discovery of new molecules or antibiotic compounds. Nanotechnology has been applied to propose new antimicrobials, revitalize existing drug options, and use strategic encapsulating agents with their biochemical characteristics, making them more effective against various bacteria. Advanced knowledge in bacterial sequencing contributes to the construction of databases, resulting in advances in bioinformatics and the development of new antimicrobials. Moreover, it enables in silico antimicrobial susceptibility testing without the need to cultivate the pathogen, reducing costs and time. This review presents new antibiotics and biomedical and technological innovations studied in recent years to develop or improve natural or synthetic antimicrobial agents to reduce bacterial growth, promote well-being, and benefit users.

Inter-plasmid transfer of antibiotic resistance genes accelerates antibiotic resistance in bacterial pathogens

Antimicrobial resistance is a major threat for public health. Plasmids play a critical role in the spread of antimicrobial resistance via horizontal gene transfer between bacterial species. However, it remains unclear how plasmids originally recruit and assemble various antibiotic resistance genes (ARGs). Here, we track ARG recruitment and assembly in clinically relevant plasmids by combining a systematic analysis of 2420 complete plasmid genomes and experimental validation. Results showed that ARG transfer across plasmids is prevalent, and 87% ARGs were observed to potentially transfer among various plasmids among 8229 plasmid-borne ARGs. Interestingly, recruitment and assembly of ARGs occur mostly among compatible plasmids within the same bacterial cell, with over 88% of ARG transfers occurring between compatible plasmids. Integron and insertion sequences drive the ongoing ARG acquisition by plasmids, especially in which IS26 facilitates 63.1% of ARG transfer events among plasmids. In vitro experiment validated the important role of IS26 involved in transferring gentamicin resistance gene aacC1 between compatible plasmids. Network analysis showed four beta-lactam genes (blaTEM-1, blaNDM-4, blaKPC-2, and blaSHV-1) shuffling among 1029 plasmids and 45 clinical pathogens, suggesting that clinically alarming ARGs transferred accelerate the propagation of antibiotic resistance in clinical pathogens. ARGs in plasmids are also able to transmit across clinical and environmental boundaries, in terms of the high-sequence similarities of plasmid-borne ARGs between clinical and environmental plasmids. This study demonstrated that inter-plasmid ARG transfer is a universal mechanism for plasmid to recruit various ARGs, thus advancing our understanding of the emergence of multidrug-resistant plasmids.

Convergence of resistance and evolutionary responses in Escherichia coli and Salmonella enterica co-inhabiting chicken farms in China

Sharing of genetic elements among different pathogens and commensals inhabiting same hosts and environments has significant implications for antimicrobial resistance (AMR), especially in settings with high antimicrobial exposure. We analysed 661 Escherichia coli and Salmonella enterica isolates collected within and across hosts and environments, in 10 Chinese chicken farms over 2.5 years using data-mining methods. Most isolates within same hosts possessed the same clinically relevant AMR-carrying mobile genetic elements (plasmids: 70.6%, transposons: 78%), which also showed recent common evolution. Supervised machine learning classifiers revealed known and novel AMR-associated mutations and genes underlying resistance to 28 antimicrobials, primarily associated with resistance in E. coli and susceptibility in S. enterica. Many were essential and affected same metabolic processes in both species, albeit with varying degrees of phylogenetic penetration. Multi-modal strategies are crucial to investigate the interplay of mobilome, resistance and metabolism in cohabiting bacteria, especially in ecological settings where community-driven resistance selection occurs.

Impacts of net cages on pollutant accumulation and its consequence on antibiotic resistance genes (ARGs) dissemination in freshwater ecosystems: Insights for sustainable urban water management

There has been increasing interest in the role of human activities in disseminating antibiotic-resistance genes (ARGs) in aquatic ecosystems. However, the influence of pollutant accumulation on anthropogenic pollutant-ARG synergistic actions is limited. This study explored the association of net cages with the propagation of anthropogenic pollutants and their consequences for influencing the enrichment of ARGs using high-throughput metagenomic sequencing. We showed that net cages could substantially impact the ecology of freshwater systems by enhancing i) ARG diversity and the tendency for ARG-horizontal gene transfer and ii) the overlap of mobile genetic elements (MGEs) with biocide-metal resistance genes (BMRGs) and ARGs. These findings suggested that the cotransfer of these three genetic determinants would be favored in net cage plots and that nonantibiotic factors such as metal(loid)s, particularly iron (Fe), displayed robust selective pressures on ARGs exerted by the net cage. The resistome risk scores of net cage sediments and biofilms were higher than those from off-net cage plots, indicating that the net cage-origin antibiotic resistome should be of great concern. The combination of deterministic and stochastic processes acting on bacterial communities could explain the higher ARG variations in cage plots (8.2%) than in off-cage plots (3.4%). Moreover, MGEs and pollutants together explained 43.3% of the total variation in ARG communities, which was higher than that of off-cage plots (8.8%), considering pollutants, environmental variables, MGEs, and assembly processes. These findings will inform the development of policies and guidelines to more effectively limit the spread of antimicrobial resistance and achieve the goal of sustainability in freshwater systems in urban areas.

Influence of age, socioeconomic status, and location on the infant gut resistome across populations

Antibiotic resistance is a growing global concern, with many ecological niches showing a high abundance of antibiotic resistance genes (ARGs), including the human gut. With increasing indications of ARGs in infants, this study aims to investigate the gut resistome profile during early life at a wider geographic level. To achieve this objective, we utilized stool samples data from 26 studies involving subjects aged up to 3 years from different geographical locations. The 32,277 Metagenome Assembled Genomes (MAGs) previously generated from shotgun sequencing reads from these studies were used for resistome analysis using RGI with the CARD database. This analysis showed that the distribution of ARGs across the countries in our study differed in alpha diversity and compositionally. In particular, the abundance of ARGs was found to vary by socioeconomic status and healthcare access and quality (HAQ) index. Surprisingly, countries having lower socioeconomic status and HAQ indices showed lower ARG abundance, which was contradictory to previous reports. Gram-negative genera, including Escherichia, Enterobacter, Citrobacter, and Klebsiella harbored a particularly rich set of ARGs, which included antibiotics that belong to the Reserve, Access or Watch category, such as glycopeptides, fluoroquinolones, sulfonamides, macrolides, and tetracyclines. We showed that ARG abundance exponentially decreased with time during the first 3 years of life. Many highly ARG-abundant species including Escherichia, Klebsiella, Citrobacter species that we observed are well-known pathobionts found in the infant gut in early life. High abundance of these species and a diverse range of ARGs in their genomes point toward the infant gut, acting as an ARG reservoir. This is a concern and further studies are needed to examine the causal effect and its consequences on long-term health.

Vaccination to Reduce Antimicrobial Resistance Burden-Data Gaps and Future Research

Antimicrobial resistance (AMR) poses an immediate danger to global health. If unaddressed, the current upsurge in AMR threatens to reverse the achievements in reducing the infectious disease-associated mortality and morbidity associated with antimicrobial treatment. Consequently, there is an urgent need for strategies to prevent or slow the progress of AMR. Vaccines potentially contribute both directly and indirectly to combating AMR. Modeling studies have indicated significant gains from vaccination in reducing AMR burdens for specific pathogens, reducing mortality/morbidity, and economic loss. However, quantifying the real impact of vaccines in these reductions is challenging because many of the study designs used to evaluate the contribution of vaccination programs are affected by significant background confounding, and potential selection and information bias. Here, we discuss challenges in assessing vaccine impact to reduce AMR burdens and suggest potential approaches for vaccine impact evaluation nested in vaccine trials.

Assessment of biofilm, enzyme production and antibiotic susceptibility of bacteria from milk pre- and post-pasteurization pipelines in Algeria

Bacterial biofilm is a major concern of dairy industry due to its association with milk contamination and its derived products. Algerian pasteurized milk shelf-life does not exceed one day, which may reflect the high level of contamination of this product and presence of extracellular enzymes such as lipases and proteases. This work aimed to investigate the microbial biodiversity in milk-processing surfaces of a dairy plant in Algeria. Therefore, stainless steel cylinders were placed in piping system of the dairy system before and after pasteurization of the milk, being removed after 7 days, for biofilm maturation and microorganism isolation and identification by mass spectrometry. Fifty-nine Gram-positive isolates were identified, namely Bacillus altitudinis, Bacillus cereus, Bacillus pumilus, Bacillus subtilis, Bacillus weithenstephanensis, Enterococcus casseliflavus, Enterococcus faecium, and Staphylococcus epidermidis. In addition, twenty-four Gram-negative isolates were identified, namely Acinetobacter schindleri Enterobacter cloacae, Enterobacter xiangfangensis, Leclercia adecarboxylata, and Raoultella ornithinolytica. Bacterial isolates showed ability for production of extracellular enzymes, being 49 % capable of both proteolytic and lipolytic activities. Milk isolates were tested for the ability to form biofilms on stainless steel. The cell numbers recovered on plate count agar plates from stainless steel biofilms ranged from 3.52 to 6.92 log10 CFU/cm2, being the maximum number detected for Enterococcus casseliflavus. Bacterial isolates showed intermediate and/or resistant profiles to multiple antibiotics. Resistance to amoxicillin, cefoxitin and/or erythromycin was commonly found among the bacterial isolates.

Targeted elimination of Vancomycin resistance gene vanA by CRISPR-Cas9 system

OBJECTIVE

The purpose of this study is to reduce the spread of the vanA gene by curing the vanA-harboring plasmid of vancomycin-resistant using the CRISPR-Cas9 system.

METHODS

Two specific spacer sequence (sgRNAs) specific was designed to target the vanA gene and cloned into plasmid CRISPR-Cas9. The role of the CRISPR-Cas system in the plasmid elimination of drug-resistance genes was verified by chemically transformation and conjugation delivery methods. Moreover, the elimination efficiency in strains was evaluated by plate counting, PCR, and quantitative real-time PCR (qPCR). Susceptibility testing was performed by broth microdilution assay and by Etest strips (bioMérieux, France) to detect changes in bacterial drug resistance phenotype after drug resistance plasmid clearance.

RESULTS

In the study, we constructed a specific prokaryotic CRISPR-Cas9 system plasmid targeting cleavage of the vanA gene. PCR and qPCR results indicated that recombinant pCas9-sgRNA plasmid can efficiently clear vanA-harboring plasmids. There was no significant correlation between sgRNA lengths and curing efficiency. In addition, the drug susceptibility test results showed that the bacterial resistance to vancomycin was significantly reduced after the vanA-containing drug-resistant plasmid was specifically cleaved by the CRISPR-Cas system. The CRISPR-Cas9 system can block the horizontal transfer of the conjugated plasmid pUC19-vanA.

CONCLUSION

In conclusion, our study demonstrated that CRISPR-Cas9 achieved plasmid clearance and reduced antimicrobial resistance. The CRISPR-Cas9 system could block the horizontal transfer of plasmid carrying vanA. This strategy provided a great potential to counteract the ever-worsening spread of the vanA gene among bacterial pathogens and laid the foundation for subsequent research using the CRISPR-Cas9 system as adjuvant antibiotic therapy.

Risk characteristics of resistome coalescence in irrigated soils and effect of natural storage of irrigation materials on risk mitigation

Irrigation and fertilization are the routinely agricultural practices but also cause resistome coalescence, by which the entire microbiomes from irrigation materials invade soil microbial community, to transfer antibiotic resistance genes (ARGs) in the coalesced soils. Although studies have reported the effect of irrigation or fertilization on the prevalence and spread of ARGs in soils, risk characteristics of resistome coalescence in irrigation system remain to be demonstrated and few has shown whether natural storage of irrigation materials will reduce resistance risks. To fill the gaps, two microscopic experiments were conducted for deeply exploring resistance risks in the soils irrigated with wastewater and manure fertilizer from a perspective of community coalescence by metagenomic analysis, and to reveal the effect of natural storage of irrigation materials on the reduction of resistance risks in the coalesced soils. Results showed irrigation and coalescence significantly increased the abundance and diversity of ARGs in the soils, and introduced some emerging resistance genes into the coalesced community, including mcr-type, tetX, qacB, and an array of genes conferring resistance to carbapenem. Procrustes analysis demonstrated microbial community was significantly correlated with the ARGs in coalesced soils, and variance partitioning analysis quantified its dominant role on shaping resistome profile in the environment. Besides ARGs, abundant and diverse mobile genetic elements (MGEs) were also identified in the coalesced soils and co-existed on the ARG-carrying contigs, implying potential transfer risk of ARGs in the irrigation system. Further, the analysis of metagenome-assembled genomes (MAGs) confirmed the risk by recovering 358 ARGs-carrying MAGs and identifying the resistant bacteria that co-carried multiple ARGs and MGEs. As expected, the natural storage of irrigation water and manure fertilizer reduced about 27%-54% of ARGs, MGEs and virulence factors in the coalesced soils, thus caused the soils to move towards lower resistance risks to a certain extent.

Metagenomic Insight into The Global Dissemination of The Antibiotic Resistome

The global crisis in antimicrobial resistance continues to grow. Estimating the risks of antibiotic resistance transmission across habitats is hindered by the lack of data on mobility and habitat-specificity. Metagenomic samples of 6092 are analyzed to delineate the unique core resistomes from human feces and seven other habitats. This is found that most resistance genes (≈85%) are transmitted between external habitats and human feces. This suggests that human feces are broadly representative of the global resistome and are potentially a hub for accumulating and disseminating resistance genes. The analysis found that resistance genes with ancient horizontal gene transfer (HGT) events have a higher efficiency of transfer across habitats, suggesting that HGT may be the main driver for forming unique but partly shared resistomes in all habitats. Importantly, the human fecal resistome is historically different and influenced by HGT and age. The most important routes of cross-transmission of resistance are from the atmosphere, buildings, and animals to humans. These habitats should receive more attention for future prevention of antimicrobial resistance. The study will disentangle transmission routes of resistance genes between humans and other habitats in a One Health framework and can identify strategies for controlling the ongoing dissemination and antibiotic resistance.

The Impact of Bamboo Consumption on the Spread of Antibiotic Resistance Genes in Giant Pandas

The spread of antibiotic resistance genes (ARGs) in the environment exacerbates the contamination of these genes; therefore, the role plants play in the transmission of resistance genes in the food chain requires further research. Giant pandas consume different bamboo parts at different times, which provides the possibility of investigating how a single food source can affect the variation in the spread of ARGs. In this study, metagenomic analysis and the Comprehensive Antibiotic Resistance Database (CARD) database were used to annotate ARGs and the differences in gut microbiota ARGs during the consumption of bamboo shoots, leaves, and culms by captive giant pandas. These ARGs were then compared to investigate the impact of bamboo part consumption on the spread of ARGs. The results showed that the number of ARGs in the gut microbiota of the subjects was highest during the consumption of bamboo leaves, while the variety of ARGs was highest during the consumption of shoots. Escherichia coli, which poses a higher risk of ARG dissemination, was significantly higher in the leaf group, while Klebsiella, Enterobacter, and Raoultella were significantly higher in the shoot group. The ARG risk brought by bamboo shoots and leaves may originate from soil and environmental pollution. It is recommended to handle the feces of giant pandas properly and regularly monitor the antimicrobial and virulence genes in their gut microbiota to mitigate the threat of antibiotic resistance.

Importance of mobile genetic elements for dissemination of antimicrobial resistance in metagenomic sewage samples across the world

We are facing an ever-growing threat from increasing antimicrobial resistance (AMR) in bacteria. To mitigate this, we need a better understanding of the global spread of antimicrobial resistance genes (ARGs). ARGs are often spread among bacteria by horizontal gene transfer facilitated by mobile genetic elements (MGE). Here we use a dataset consisting of 677 metagenomic sequenced sewage samples from 97 countries or regions to study how MGEs are geographically distributed and how they disseminate ARGs worldwide. The ARGs, MGEs, and bacterial abundance were calculated by reference-based read mapping. We found systematic differences in the abundance of MGEs and ARGs, where some elements were prevalent on all continents while others had higher abundance in separate geographic areas. Different MGEs tended to be localized to temperate or tropical climate zones, while different ARGs tended to separate according to continents. This suggests that the climate is an important factor influencing the local flora of MGEs. MGEs were also found to be more geographically confined than ARGs. We identified several integrated MGEs whose abundance correlated with the abundance of ARGs and bacterial genera, indicating the ability to mobilize and disseminate these genes. Some MGEs seemed to be more able to mobilize ARGs and spread to more bacterial species. The host ranges of MGEs seemed to differ between elements, where most were associated with bacteria of the same family. We believe that our method could be used to investigate the population dynamics of MGEs in complex bacterial populations.

The migration regularity and removal mechanism of antibiotic resistance genes during in situ enzymatic hydrolysis and anaerobic digestion of food waste

This study developed a high efficiency compound enzyme (fungal mash) produced in situ from food waste (FW) used for improving hydrolysis and anaerobic digestion (AD) efficiency of FW. Results showed that the soluble COD and methane yield were respectively increased by 67.80% and 16.58% after 24 h in situ enzymatic hydrolysis of food waste by fungal mash. Furthermore, most of target ARGs in FW were also reduced by 45-94% after 24 h in situ enzymatic hydrolysis, while the total tested ARGs and intI1 were respectively further removed by 44-55% and 21-73% in subsequent AD process. In-depth analysis showed that fungal mash could effectively reduce potential hosts and control the horizontal transfer of ARGs during the in situ enzymatic hydrolysis and AD process. Ultimately, correlation analysis and redundancy analysis indicated that the evolution of bacterial communities and changes in intI1 where the common driving forces for the fate of ARGs.

What are the missing pieces needed to stop antibiotic resistance?

As recognized by several international agencies, antibiotic resistance is nowadays one of the most relevant problems for human health. While this problem was alleviated with the introduction of new antibiotics into the market in the golden age of antimicrobial discovery, nowadays few antibiotics are in the pipeline. Under these circumstances, a deep understanding on the mechanisms of emergence, evolution and transmission of antibiotic resistance, as well as on the consequences for the bacterial physiology of acquiring resistance is needed to implement novel strategies, beyond the development of new antibiotics or the restriction in the use of current ones, to more efficiently treat infections. There are still several aspects in the field of antibiotic resistance that are not fully understood. In the current article, we make a non-exhaustive critical review of some of them that we consider of special relevance, in the aim of presenting a snapshot of the studies that still need to be done to tackle antibiotic resistance.