Diversity and antibiotic resistance of Aeromonas spp. in drinking and waste water treatment plants

What is the Difference between Conventional Drinking Water, Potable Reuse Water, and Nonpotable Reuse Water? A Microbiome Perspective

As water reuse applications expand, there is a need for more comprehensive means to assess water quality. Microbiome analysis could provide the ability to supplement fecal indicators and pathogen profiling toward defining a "healthy" drinking water microbiota while also providing insight into the impact of treatment and distribution. Here, we utilized 16S rRNA gene amplicon sequencing to identify signature features in the composition of microbiota across a wide spectrum of water types (potable conventional, potable reuse, and nonpotable reuse). A clear distinction was found in the composition of microbiota as a function of intended water use (e.g., potable vs nonpotable) across a very broad range of U.S. water systems at both the point of compliance (Betadisper p > 0.01; ANOSIM p < 0.01, r-stat = 0.71) and point of use (Betadisper p > 0.01; ANOSIM p < 0.01, r-stat = 0.41). Core and discriminatory analysis further served in identifying distinct differences between potable and nonpotable water microbiomes. Taxa were identified at both the phylum (Desulfobacterota, Patescibacteria, and Myxococcota) and genus (Aeromonas and NS11.12_marine_group) levels that effectively discriminated between potable and nonpotable waters, with the most discriminatory taxa being core/abundant in nonpotable waters (with few exceptions, such as Ralstonia being abundant in potable conventional waters). The approach and findings open the door to the possibility of microbial community signature profiling as a water quality monitoring approach for assessing efficacy of treatments and suitability of water for intended use/reuse application.

Two colistin resistance-producing Aeromonas strains, isolated from coastal waters in Zhejiang, China: characteristics, multi-drug resistance and pathogenicity

Introduction

Aeromonas spp. are ubiquitous inhabitants of ecosystems, and many species are opportunistically pathogenic to humans and animals. Multidrug-resistant (MDR) Aeromonas species have been widely detected in hospitals, urban rivers, livestock, and aquatic animals.

Results

In this study, we identified two Aeromonas isolates, namely Aeromonas veronii 0728Q8Av and Aeromonas caviae 1029Y16Ac, from coastal waters in Zhejiang, China. Both isolates exhibited typical biochemical characteristics and conferred MDR to 11 kinds of antibiotics, remaining susceptible to ceftazidime. Whole-genome sequencing revealed that both isolates harbored multiple antibiotic resistance genes (ARGs) and several mobile genetic elements (MGEs) on the chromosomes, each containing a resistance genomic island (GI), a typical class 1 integron, a transposon, and various insertion sequences (ISs). Most ARGs were situated within the multiple resistance GI, which contained a class 1 integron and a transposon in both Aeromonas isolates. Furthermore, a chromosomal mcr-3.16 gene was identified in A. veronii 0728Q8Av, while a chromosomal mcr-3.3 was found in A. caviae 1029Y16Ac. Both mcr-3 variants were not located within but were distanced from the multidrug resistance GI on the chromosome, flanking by multiple ISs. In addition, a mcr-3-like was found adjacent to mcr-3.16 to form a tandem mcr-3.16-mcr-3-like-dgkA structure; yet, Escherichia coli carrying the recombinants of mcr-3-like did not exhibit resistance to colistin. And an incomplete mcr-3-like was found adjacent to mcr-3.3 in A. caviae 1029Y16Ac, suggesting the possibility that mcr-3 variants originated from Aeromonas species. In vivo bacterial pathogenicity test indicated that A. veronii 0728Q8Av exhibited moderate pathogenicity towards infected ayu, while A. caviae 1029Y16Ac was non-virulent.

Discussion

Thus, both Aeromonas species deserve further attention regarding their antimicrobial resistance and pathogenicity.

Bioaerosol Sampling Devices and Pretreatment for Bacterial Characterization: Theoretical Differences and a Field Experience in a Wastewater Treatment Plant

Studies on bioaerosol bacterial biodiversity have relevance in both ecological and health contexts, and molecular methods, such as 16S rRNA gene-based barcoded sequencing, provide efficient tools for the analysis of airborne bacterial communities. Standardized methods for sampling and analysis of bioaerosol DNA are lacking, thus hampering the comparison of results from studies implementing different devices and procedures. Three samplers that use gelatin filtration, swirling aerosol collection, and condensation growth tubes for collecting bioaerosol at an aeration tank of a wastewater treatment plant in Trieste (Italy) were used to determine the bacterial biodiversity. Wastewater samples were collected directly from the untreated sewage to obtain a true representation of the microbiological community present in the plant. Different samplers and collection media provide an indication of the different grades of biodiversity, with condensation growth tubes and DNA/RNA shieldTM capturing the richer bacterial genera. Overall, in terms of relative abundance, the air samples have a lower number of bacterial genera (64 OTUs) than the wastewater ones (75 OTUs). Using the metabarcoding approach to aerosol samples, we provide the first preliminary step toward the understanding of a significant diversity between different air sampling systems, enabling the scientific community to orient research towards the most informative sampling strategy.

Involvement of functional metabolism promotes the enrichment of antibiotic resistome in drinking water: Based on the PICRUSt2 functional prediction

Biofilters are the important source and sink of antibiotic resistance genes (ARGs) and antibiotic resistance bacteria (ARB) in the drinking water. Current studies generally ascribed the prevalence of BAR in biofilter from the perspective of gene behavior, i.e. horizontal gene transfer (HGT), little attentions have been paid on the ARGs carrier- ARB. In this study, we proposed the hypothesis that ARB participating in pollutant metabolism processes and becoming dominant is an important way for the enrichment of ARGs. To verify this, the antibiotic resistome and bacterial functional metabolic pathways of a sand filter was profiled using heterotrophic bacterial plate counting method (HPC), high-throughput qPCR, Illumina Hiseq sequencing and PICRUSt2 functional prediction. The results illustrated a significant leakage of ARB in the effluent of the sand filter with an average absolute abundance of approximately 102-103 CFU/mL. Further contribution analysis revealed that the dominant genera, such as Acinetobacter spp., Aeromonas spp., Elizabethkingia spp., and Bacillus spp., were primary ARGs hosts, conferring resistance to multiple antibiotics including sulfamethoxazole, tetracycline and β-lactams. Notably, these ARGs hosts were involved in nitrogen metabolism, including extracellular nitrate/nitrite transport and nitrite reduction, which are crucial in nitrification and denitrification in biofilters. For example, Acinetobacter spp., the dominant bacteria in the filter (relative abundance 69.97 %), contributed the majority of ARGs and 53.79 % of nitrite reduction function. That is, ARB can predominate by participating in the nitrogen metabolism pathways, facilitating the enrichment of ARGs. These findings provide insights into the stable presence of ARGs in biofilters from a functional metabolism perspective, offering a significant supplementary to the mechanisms of the emergence, maintenance, and transmission of BARin drinking water.

Exploring Aeromonas dhakensis in Aldabra giant tortoises: a debut report and genetic characterization

Aeromonas dhakensis (A. dhakensis) is becoming an emerging pathogen worldwide, with an increasingly significant role in animals and human health. It is a ubiquitous bacteria found in terrestrial and aquatic milieus. However, there have been few reports of reptile infections. In this study, a bacterial strain isolated from a dead Aldabra giant tortoise was identified as A. dhakensis HN-1 through clinical observation, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS), and gene sequencing analysis. Subsequently, to evaluate its pathogenicity, the detection of virulence genes and mice infection experiments were performed. A. dhakensis HN-1 was found to contain seven virulence genes, including alt, ela, lip, act, aerA, fla, and hlyA. Mice infected with A. dhakensis HN-1 exhibited hemorrhage of varying degrees in multiple organs. The half-maximal lethal dose (LD50) value of A. dhakensis HN-1 for mice was estimated to be 2.05 × 107 colony forming units (CFU)/mL. The antimicrobial susceptibility test revealed that A. dhakensis HN-1 was resistant to amoxicillin, penicillin, ampicillin and erythromycin. This is the first report of A. dhakensis in Aldabra giant tortoises, expanding the currently known host spectrum. Our findings emphasize the need for One Health surveillance and extensive research to reduce the spread of A. dhakensis across the environment, humans, and animals.

Horizontal transfer potential of antibiotic resistance genes in wastewater treatment plants unraveled by microfluidic-based mini-metagenomics

Wastewater treatment plants (WWTPs) are known to harbor antibiotic resistance genes (ARGs), which can potentially spread to the environment and human populations. However, the extent and mechanisms of ARG transfer in WWTPs are not well understood due to the high microbial diversity and limitations of molecular techniques. In this study, we used a microfluidic-based mini-metagenomics approach to investigate the transfer potential and mechanisms of ARGs in activated sludge from WWTPs. Our results show that while diverse ARGs are present in activated sludge, only a few highly similar ARGs are observed across different taxa, indicating limited transfer potential. We identified two ARGs, ermF and tla-1, which occur in a variety of bacterial taxa and may have high transfer potential facilitated by mobile genetic elements. Interestingly, genes that are highly similar to the sequences of these two ARGs, as identified in this study, display varying patterns of abundance across geographic regions. Genes similar to ermF found are widely found in Asia and the Americas, while genes resembling tla-1 are primarily detected in Asia. Genes similar to both genes are barely detected in European WWTPs. These findings shed light on the limited horizontal transfer potential of ARGs in WWTPs and highlight the importance of monitoring specific ARGs in different regions to mitigate the spread of antibiotic resistance.

Nosocomial infections by diverse carbapenemase-producing Aeromonas hydrophila associated with combination of plumbing issues and heat waves

BACKGROUND

Aquatic opportunistic pathogen Aeromonas hydrophila, known to persist in low-nutrient chlorinated waters, can cause life-threatening infections. Two intensive care units experienced a cluster of Aeromonas infections following outdoor temperature spikes coinciding with recurrent plumbing issues, with fatalities due to severe underlying comorbidities co-occurring with extensively-drug resistant (XDR) Aeromonas.

METHODS

We investigated this cluster using whole genome sequencing to assess genetic relatedness of isolates and identify antimicrobial resistance determinants. Three A. hydrophila were isolated from patients staying in or adjacent to rooms with plumbing issues during or immediately after periods of elevated outdoor temperatures. Sinks and faucets were swabbed for culture.

RESULTS

All A. hydrophila clinical isolates exhibited carbapenem resistance but were not genetically related. Diverse resistance determinants corresponding to extensively-drug resistant were found, including co-occurring KPC-3 and VIM-2, OXA-232, and chromosomal CphA-like carbapenemase genes, contributing to major treatment challenges. All 3 patients were treated with multiple antibiotic regimens to overcome various carbapenemase classes and expired due to underlying comorbidities. Environmental culture yielded no Aeromonas.

CONCLUSIONS

While the investigation revealed no singular source of contamination, it supports a possible link between plumbing issues, elevated outdoor temperatures and incidence of nosocomial Aeromonas infections. The diversity of carbapenemase genes detected in these wastewater-derived Aeromonas warrants heightened infection prevention precautions during periods of plumbing problems especially with heat waves.

Parabens as environmental contaminants of aquatic systems affecting water quality and microbial dynamics

Among different pollutants of emerging concern, parabens have gained rising interest due to their widespread detection in water sources worldwide. This occurs because parabens are used in personal care products, pharmaceuticals, and food, in which residues are generated and released into aquatic environments. The regulation of the use of parabens varies across different geographic regions, resulting in diverse concentrations observed globally. Concentrations of parabens exceeding 100 μg/L have been found in wastewater treatment plants and surface waters while drinking water (DW) sources typically exhibit concentrations below 6 μg/L. Despite their low levels, the presence of parabens in DW is a potential exposure route for humans, raising concerns for both human health and environmental microbiota. Although a few studies have reported alterations in the functions and characteristics of microbial communities following exposure to emerging contaminants, the impact of the exposure to parabens by microbial communities, particularly biofilm colonizers, remains largely understudied. This review gathers the most recent information on the occurrence of parabens in water sources, as well as their effects on human health and aquatic organisms. The interactions of parabens with microbial communities are reviewed for the first time, filling the knowledge gaps on the effects of paraben exposure on microbial ecosystems and their impact on disinfection tolerance and antimicrobial resistance, with potential implications for public health.

Removal of intI1, ARGs, and SARS-CoV-2 and changes in bacterial communities in four sewage treatment facilities

Currently, discharge regulations for wastewater treatment plants (WWTPs) are based on conventional parameters, but more is needed to ensure safe water reuse. In particular, emerging pollutants, as antimicrobials and antibiotic resistance genes (ARGs), are not considered. This research focuses on the fate of emerging biological contaminants during wastewater treatment in Mexico City. intI1 and the ARGs cphA-02, OXA-10 and sul1 were analyzed by qPCR; pathogenic bacteria species were characterized by high throughput sequencing of complete 16S rRNA gene, and fragments of SARS-CoV-2 were quantified by RT-qPCR. Conventional parameters (chemical oxygen demand and coliform bacteria) were also determined. Two sampling campaigns (rainy and dry seasons) were carried out in four municipal WWTPs in Mexico City, representing five biological treatment processes: conventional activated sludge, extended aeration activated sludge, membrane bioreactor, direct anaerobic digestion, and constructed wetland, followed by ultraviolet light or chlorine disinfection. In most cases, gene fragments of SARS-CoV-2 were eliminated below the detection limit of RT-qPCR. The abundance of intI1 positively correlated with the sul1, OXA-10, and cphA-02 abundances; intI1 and the ARGs here studied were partially removed in the WWTPs, and in most cases, the number of copies per second discarded in the sludge were higher those in the effluent. The treatment processes decreased the abundance of dominant bacterial groups in the raw wastewater, while enriching bacterial groups in the effluent and the biological sludge, with possible pollutant removal capabilities. Bacterial communities in the raw wastewater showed the predominance of the genus Arcobacter (from 62.4 to 86.0 %) containing potentially pathogenic species. Additionally, DNA of some species persisted after the treatment processes: A. johnsonii, A. junii, A. caviae, A. hydrophila, A. veronii, A. butzleri, A. cryaerophilus, Chryseobacterium indologenes, Hafnia paralvei, M. osloensis, Pseudomonas putida and Vibrio cholerae, which deserves special attention in future regulation for safe water reuse.

Anthropogenic contributions to antibiotic resistance gene pollution in household drinking water revealed by machine-learning-based source-tracking

Although the presence of antibiotic resistance genes (ARGs) in drinking water and their potential horizontal gene transfer to pathogenic microbes are known to pose a threat to human health, their pollution levels and potential anthropogenic sources are poorly understood. In this study, broad-spectrum ARG profiling combined with machine-learning-based source classification SourceTracker was performed to investigate the pollution sources of ARGs in household drinking water collected from 95 households in 47 cities of eight countries/regions. In total, 451 ARG subtypes belonging to 19 ARG types were detected with total abundance in individual samples ranging from 1.4 × 10-4 to 1.5 × 10° copies per cell. Source tracking analysis revealed that many ARGs were highly contributed by anthropogenic sources (37.1%), mainly wastewater treatment plants. The regions with the highest detected ARG contribution from wastewater (∼84.3%) used recycled water as drinking water, indicating the need for better ARG control strategies to ensure safe water quality in these regions. Among ARG types, sulfonamide, rifamycin and tetracycline resistance genes were mostly anthropogenic in origin. The contributions of anthropogenic sources to the 20 core ARGs detected in all of the studied countries/regions varied from 36.6% to 84.1%. Moreover, the anthropogenic contribution of 17 potential mobile ARGs identified in drinking water was significantly higher than other ARGs, and metagenomic assembly revealed that these mobile ARGs were carried by diverse potential pathogens. These results indicate that human activities have exacerbated the constant input and transmission of ARGs in drinking water. Our further risk classification framework revealed three ARGs (sul1, sul2 and aadA) that pose the highest risk to public health given their high prevalence, anthropogenic sources and mobility, facilitating accurate monitoring and control of anthropogenic pollution in drinking water.

Antibiotic Resistance in Selected Emerging Bacterial Foodborne Pathogens-An Issue of Concern?

Antibiotic resistance (AR) and multidrug resistance (MDR) have been confirmed for all major foodborne pathogens: Campylobacter spp., Salmonella spp., Escherichia coli and Listeria monocytogenes. Of great concern to scientists and physicians are also reports of antibiotic-resistant emerging food pathogens-microorganisms that have not previously been linked to food contamination or were considered epidemiologically insignificant. Since the properties of foodborne pathogens are not always sufficiently recognized, the consequences of the infections are often not easily predictable, and the control of their activity is difficult. The bacteria most commonly identified as emerging foodborne pathogens include Aliarcobacter spp., Aeromonas spp., Cronobacter spp., Vibrio spp., Clostridioides difficile, Escherichia coli, Mycobacterium paratuberculosis, Salmonella enterica, Streptocccus suis, Campylobacter jejuni, Helicobacter pylori, Listeria monocytogenes and Yersinia enterocolitica. The results of our analysis confirm antibiotic resistance and multidrug resistance among the mentioned species. Among the antibiotics whose effectiveness is steadily declining due to expanding resistance among bacteria isolated from food are β-lactams, sulfonamides, tetracyclines and fluoroquinolones. Continuous and thorough monitoring of strains isolated from food is necessary to characterize the existing mechanisms of resistance. In our opinion, this review shows the scale of the problem of microbes related to health, which should not be underestimated.

Mapping human pathogens in wastewater using a metatranscriptomic approach

The monitoring of cities' wastewaters for the detection of potentially pathogenic viruses and bacteria has been considered a priority during the COVID-19 pandemic to monitor public health in urban environments. The methodological approaches frequently used for this purpose include deoxyribonucleic acid (DNA)/Ribonucleic acid (RNA) isolation followed by quantitative polymerase chain reaction (qPCR) and reverse transcription (RT)‒qPCR targeting pathogenic genes. More recently, the application of metatranscriptomic has opened opportunities to develop broad pathogenic monitoring workflows covering the entire pathogenic community within the sample. Nevertheless, the high amount of data generated in the process requires an appropriate analysis to detect the pathogenic community from the entire dataset. Here, an implementation of a bioinformatic workflow was developed to produce a map of the detected pathogenic bacteria and viruses in wastewater samples by analysing metatranscriptomic data. The main objectives of this work was the development of a computational methodology that can accurately detect both human pathogenic virus and bacteria in wastewater samples. This workflow can be easily reproducible with open-source software and uses efficient computational resources. The results showed that the used algorithms can predict potential human pathogens presence in the tested samples and that active forms of both bacteria and virus can be identified. By comparing the computational method implemented in this study to other state-of-the-art workflows, the implementation analysis was faster, while providing higher accuracy and sensitivity. Considering these results, the processes and methods to monitor wastewater for potential human pathogens can become faster and more accurate. The proposed workflow is available at https://github.com/waterpt/watermonitor and can be implemented in currently wastewater monitoring programs to ascertain the presence of potential human pathogenic species.

Occurrence of Aeromonas Species in the Cutaneous Mucus of Barbour’s Seahorses (Hippocampus barbouri) as Revealed by High-Throughput Sequencing

Although several studies have described the bacterial community composition associated with marine fish, there is limited information related to seahorses. Moreover, previous studies have demonstrated that the skin microbiota is useful for determining health status and common disorders in the host. This study, therefore, aimed to explore the skin bacterial community composition in Barbour’s seahorse (Hippocampus barbouri) using high-throughput sequencing of 16S ribosomal RNA genes. Water and sediment samples from the surrounding environment were also analyzed for comparative purposes. The results revealed that sequences affiliated with the Shewanellaceae family were dominant in the skin of female Barbour’s seahorses and sediment samples, whereas sequences affiliated with the Bacillaceae family were dominant in the skin of male Barbour’s seahorses. Interestingly, sequences affiliated with the Aeromonas genus were found in the skin of Barbour’s seahorses, whose abundance was slightly similar between the female and male specimens. Further comparative analysis showed that the presence of Aeromonas species in the skin of Barbour’s seahorses was strongly influenced by the surrounding sediment. Given that some Aeromonas species are known to be important pathogens in humans and fish, these results may be used for further research on the dependency of the skin microbial composition on the environment as well as determine whether the presence of Aeromonas and other detected species has implications on seahorse health.

Multidrug-resistant Aeromonas bacteria prevalence in Nile tilapia broodstock

BACKGROUND

Aeromonas hydrophila is an opportunistic pathogen. Thus, it has received significant attention mainly in the fish sectors with high production scales. Nile tilapia broodstock confined in the environment of fish hatcheries can be stressed. Hence, they are vulnerable to A. hydrophila.

RESULTS

Sequencing of the gyr B gene revealed the presence of 18 different A. hydrophila strains (kdy 10,620-10,637), which were deposited in the NCBI under accession numbers ON745861-ON745878. The median lethal doses of the isolates ranged from 2.62 × 10⁴ to 3.02 × 10⁶ CFU/mL. Antibiotic resistant genes, sulfonamide (sul1) and tetracycline (tetA) were found in the eighteen isolates. Approximately 83.3% of A. hydrophila strains were sensitive to ciprofloxacin and florfenicol. Further, eight A. hydrophila strains had high MDR indices at 0.27-0.45. All isolates presented with hemolysin activity. However, only 72.22% of them had proteolytic activity, and only 61.11% could form biofilms. Bacterial isolates harbored different pattern virulence genes, the heat-stable cytotonic enterotoxin (ast), cytotoxic enterotoxin (act), and hemolysin (hly) genes were the most prevalent. Also, a trial to inhibit bacterial growth was conducted using titanium dioxide nanoparticles (TiO₂ NPs) with three sizes (13, 32, and 123 nm). If A. hydrophila strains with a high MDR index were tested against TiO₂ NPs (20 µg/mL) for 1, 12, and 24 h, those with a small size had a greater bactericidal action than large ones. Bacterial strains were inhibited at different percentages in response to TiO₂ NP treatment.

CONCLUSIONS

Nile tilapia broodstock, mortality is associated with different A. hydrophila strains, which harbored virulent and MDR genes. Furthermore, TiO₂ NPs had bactericidal activity, thereby resulting in a considerable reduction in bacterial load.

Characterization of Third Generation Cephalosporin- and Carbapenem-Resistant Aeromonas Isolates from Municipal and Hospital Wastewater

Antibiotic resistance (AR) remains one of the greatest threats to global health, and Aeromonas species have the potential to spread AR in the aquatic environment. The spread of resistance to antibiotics important to human health, such as third-generation cephalosporins (3GCs) and carbapenems, is of great concern. We isolated and identified 15 cefotaxime (3GC)- and 51 carbapenem-resistant Aeromonas spp. from untreated hospital and treated municipal wastewater in January 2020. The most common species were Aeromonas caviae (58%), A. hydrophila (17%), A. media (11%), and A. veronii (11%). Almost all isolates exhibited a multidrug-resistant phenotype and harboured a diverse plasmidome, with the plasmid replicons ColE, IncU, and IncR being the most frequently detected. The most prevalent carbapenemase gene was the plasmid-associated blaKPC-2 and, for the first time, the blaVIM-2, blaOXA-48, and blaIMP-13 genes were identified in Aeromonas spp. Among the 3GC-resistant isolates, the blaGES-5 and blaMOX genes were the most prevalent. Of the 10 isolates examined, three were capable of transferring carbapenem resistance to susceptible recipient E. coli. Our results suggest that conventionally treated municipal and untreated hospital wastewater is a reservoir for 3GC- and carbapenem-resistant, potentially harmful Aeromonas spp. that can be introduced into aquatic systems and pose a threat to both the environment and public health.

Pollution and health-risk assessments of Cr-contaminated soils from a tannery waste lagoon, Hebei, north China: With emphasis on Cr speciation

In this paper, heavy metals (i.e., V, Cr, Co, Cu, Zn, Cd, Pb, and Sb) in soils from a tannery waste lagoon, Hebei, north China were investigated. Element concentrates were determined by a portable X-ray fluorescence in situ and an inductively coupled plasma mass spectrometry in the lab. Two sets of indexes, including geological accumulation index, contamination factor, and pollution load index, and hazard quotient and total carcinogenic risk were adopted to evaluate the pollution and health-risk of heavy metals. A scanning electron microscopy in conjunction with an energy dispersive X-ray spectroscopy and an X-ray photoelectron spectroscopy was used to observe chromium occurrence and speciation. With an average of 6493.11 mg/kg, chromium contents in the lagoon soils reached up to 12971.19 mg/kg, 211-times higher than the threshold of Chinese soils (61.00 mg/kg). Elevated Cr contents resulted in significantly high pollution and noncarcinogenic and carcinogenic risks in the studied area. Chromium in most soils occurred predominately as Cr³⁺ (60-74%), and to a lesser extent, Cr⁶⁺. The mechanism responsible for decreasing Cr⁶⁺ percentages in soils with increasing depth was summarized: Cr⁶⁺ favors aqueous environment; soil moisture decreased with increasing depth; in soils especially in the lower portion, Cr⁶⁺ was reduced by Fe⁰ and Fe², transforming into Cr³⁺ and Fe³⁺. In addition, the alkaline condition promoted Cr³⁺ to precipitate, resulting more Cr³⁺ absorbing in soils. The intimate association of Cr and Fe in soils (i.e., Cr mainly occurred in Fe oxides and dolomite) further confirmed our assumptions. A combined application of microorganism (e.g., Aeromonas hydrophila) and biochar (prepared from maize stalk or peanut shells) were recommended to alleviate Cr pollution in the soils.

Characterization of virulence and antimicrobial resistance genes of Aeromonas media strain SD/21-15 from marine sediments in comparison with other Aeromonas spp

Aeromonas media is a Gram-negative bacterium ubiquitously found in aquatic environments. It is a foodborne pathogen associated with diarrhea in humans and skin ulceration in fish. In this study, we used whole genome sequencing to profile all antimicrobial resistance (AMR) and virulence genes found in A. media strain SD/21-15 isolated from marine sediments in Denmark. To gain a better understanding of virulence and AMR genes found in several A. media strains, we included 24 whole genomes retrieved from the public databanks whose isolates originate from different host species and environmental samples from Asia, Europe, and North America. We also compared the virulence genes of strain SD/21-15 with A. hydrophila, A. veronii, and A. salmonicida reference strains. We detected Msh pili, tap IV pili, and lateral flagella genes responsible for expression of motility and adherence proteins in all isolates. We also found hylA, hylIII, and TSH hemolysin genes in all isolates responsible for virulence in all isolates while the aerA gene was not detected in all A. media isolates but was present in A. hydrophila, A. veronii, and A. salmonicida reference strains. In addition, we detected LuxS and mshA-Q responsible for quorum sensing and biofilm formation as well as the ferric uptake regulator (Fur), heme and siderophore genes responsible for iron acquisition in all A. media isolates. As for the secretory systems, we found all genes that form the T2SS in all isolates while only the vgrG1, vrgG3, hcp, and ats genes that form parts of the T6SS were detected in some isolates. Presence of bla MOX-9 and bla OXA-427 β-lactamases as well as crp and mcr genes in all isolates is suggestive that these genes were intrinsically encoded in the genomes of all A. media isolates. Finally, the presence of various transposases, integrases, recombinases, virulence, and AMR genes in the plasmids examined in this study is suggestive that A. media has the potential to transfer virulence and AMR genes to other bacteria. Overall, we anticipate these data will pave way for further studies on virulence mechanisms and the role of A. media in the spread of AMR genes.

Potential Pathogenicity of Aeromonas spp. Recovered in River Water, Soil, and Vegetation from a Natural Recreational Area

The genus Aeromonas is widely distributed in aquatic environments and is recognized as a potential human pathogen. Some Aeromonas species are able to cause a wide spectrum of diseases, mainly gastroenteritis, skin and soft-tissue infections, bacteremia, and sepsis. Currently, untreated river water is used for irrigation and recreational purposes. In this study, the Aeromonas spp. present in a river recreational environment was investigated by quantifying its presence in water, soil, and vegetation using three techniques: qPCR, plate counting in selective ADA medium, and Most Probable Number, in parallel. The presence of clones in the three types of samples was elucidated through genotyping with the ERIC-PCR technique, whereas the identification of the isolated Aeromonas was carried out by sequencing the rpoD gene. Finally, the pathogenic potential of some of the strains was explored by studying the presence and expression of virulence genes characteristic of the genus, their antimicrobial susceptibility profile, as well as the quantification of their cell damage and intracellular survival in an in vitro macrophages infection model. The results showed the presence of Aeromonas in all samples with the three quantification methods, with Aeromonas popoffii being the most prevalent species. The presence of strains with the same genotype (ERIC-PCR) was also confirmed in different samples. Some of the strains showed a high level of cell damage and intracellular bacterial survival, as well as the presence of various virulence factors. Furthermore, these strains showed resistance to some of the antibiotics tested and used therapeutically in both humans and animals. These results indicate that the presence of Aeromonas in this environment may represent a biosanitary risk that could be a public health problem.

Urbanization promotes specific bacteria in freshwater microbiomes including potential pathogens

Freshwater ecosystems are characterized by complex and highly dynamic microbial communities that are strongly structured by their local environment and biota. Accelerating urbanization and growing city populations detrimentally alter freshwater environments. To determine differences in freshwater microbial communities associated with urbanization, full-length 16S rRNA gene PacBio sequencing was performed in a case study from surface waters and sediments from a wastewater treatment plant, urban and rural lakes in the Berlin-Brandenburg region, Northeast Germany. Water samples exhibited highly habitat specific bacterial communities with multiple genera showing clear urban signatures. We identified potentially harmful bacterial groups associated with environmental parameters specific to urban habitats such as Alistipes, Escherichia/Shigella, Rickettsia and Streptococcus. We demonstrate that urbanization alters natural microbial communities in lakes and, via simultaneous warming and eutrophication and creates favourable conditions that promote specific bacterial genera including potential pathogens. Our findings are evidence to suggest an increased potential for long-term health risk in urbanized waterbodies, at a time of rapidly expanding global urbanization. The results highlight the urgency for undertaking mitigation measures such as targeted lake restoration projects and sustainable water management efforts.

Role of environmental stresses in elevating resistance mutations in bacteria: Phenomena and mechanisms

Mutations are an important origin of antibiotic resistance in bacteria. While there is increasing evidence showing promoted resistance mutations by environmental stresses, no retrospective research has yet been conducted on this phenomenon and its mechanisms. Herein, we summarized the phenomena of stress-elevated resistance mutations in bacteria, generalized the regulatory mechanisms and discussed the environmental and human health implications. It is shown that both chemical pollutants, such as antibiotics and other pharmaceuticals, biocides, metals, nanoparticles and disinfection byproducts, and non-chemical stressors, such as ultraviolet radiation, electrical stimulation and starvation, are capable of elevating resistance mutations in bacteria. Notably, resistance mutations are more likely to occur under sublethal or subinhibitory levels of these stresses, suggesting a considerable environmental concern. Further, mechanisms for stress-induced mutations are summarized in several points, namely oxidative stress, SOS response, DNA replication and repair systems, RpoS regulon and biofilm formation, all of which are readily provoked by common environmental stresses. Given bacteria in the environment are confronted with a variety of unfavorable conditions, we propose that the stress-elevated resistance mutations are a universal phenomenon in the environment and represent a nonnegligible risk factor for ecosystems and human health. The present review identifies a need for taking into account the pollutants' ability to elevate resistance mutations when assessing their environmental and human health risks and highlights the necessity of including resistance mutations as a target to prevent antibiotic resistance evolution.

Antimicrobial Resistance Monitoring of Water Environments: A Framework for Standardized Methods and Quality Control

Antimicrobial resistance (AMR) is a grand societal challenge with important dimensions in the water environment that contribute to its evolution and spread. Environmental monitoring could provide vital information for mitigating the spread of AMR; this includes assessing antibiotic resistance genes (ARGs) circulating among human populations, identifying key hotspots for evolution and dissemination of resistance, informing epidemiological and human health risk assessment models, and quantifying removal efficiencies by domestic wastewater infrastructure. However, standardized methods for monitoring AMR in the water environment will be vital to producing the comparable data sets needed to address such questions. Here we sought to establish scientific consensus on a framework for such standardization, evaluating the state of the science and practice of AMR monitoring of wastewater, recycled water, and surface water, through a literature review, survey, and workshop leveraging the expertise of academic, governmental, consulting, and water utility professionals.

Antimicrobial Resistance Monitoring of Water Environments: A Framework for Standardized Methods and Quality Control

Antimicrobial resistance (AMR) is a grand societal challenge with important dimensions in the water environment that contribute to its evolution and spread. Environmental monitoring could provide vital information for mitigating the spread of AMR; this includes assessing antibiotic resistance genes (ARGs) circulating among human populations, identifying key hotspots for evolution and dissemination of resistance, informing epidemiological and human health risk assessment models, and quantifying removal efficiencies by domestic wastewater infrastructure. However, standardized methods for monitoring AMR in the water environment will be vital to producing the comparable data sets needed to address such questions. Here we sought to establish scientific consensus on a framework for such standardization, evaluating the state of the science and practice of AMR monitoring of wastewater, recycled water, and surface water, through a literature review, survey, and workshop leveraging the expertise of academic, governmental, consulting, and water utility professionals.

Aeromonas and Human Health Disorders: Clinical Approaches

The genus Aeromonas comprises more than 30 Gram-negative bacterial species and naturally inhabitants from aquatic environments. These microorganisms, commonly regarded as pathogens of fish and several other animals, have been gaining prominence on medical trial due to its ability to colonize and infect human beings. Besides water, Aeromonas are widely spreaded on most varied sources like soil, vegetables, and food; Although its opportunistic nature, they are able to cause infections on immunocompromised or immunocompetent patients. Aeromonas species regarded as potential human pathogens are usually A. hydrophila, A. caviae, and A. veronii biovar sobria. The main clinical manifestations are gastrointestinal tract disorders, wound, and soft tissue infections, as well as septicemia. Regarding to antibiotic responses, the bacteria present a diversified susceptibility profile and show inherence resistance to ampicillin. Aeromonas, as an ascending genus in microbiology, has been carefully studied aiming comprehension and development of methods for detection and medical intervention of infectious processes, not fully elucidated in medicine. This review focuses on current clinical knowledge related to human health disorders caused by Aeromonas to contribute on development of efficient approaches able to recognize and impair the pathological processes.

Plasmidome analysis of a hospital effluent biofilm: Status of antibiotic resistance

Plasmids are widely involved in the dissemination of characteristics within bacterial communities. Their genomic content can be assessed by high-throughput sequencing of the whole plasmid fraction of an environment, the plasmidome. In this study, we analyzed the plasmidome of a biofilm formed in the effluents of the teaching hospital of Clermont-Ferrand (France). Our analysis discovered >350 new complete plasmids, with a length ranging from 1219 to 40,193 bp. Forty-two plasmid incompatibility (Inc) groups were found among all the plasmid contigs. Ten large plasmids, described here in detail, were reconstructed from plasmid contigs, seven of which carried antibiotic resistance genes. Four plasmids potentially confer resistance to numerous families of antibiotics, including carbapenems, aminoglycosides, colistin, and chloramphenicol. Most of these plasmids were affiliated to Proteobacteria, a phylum of Gram-negative bacteria. This study therefore illustrates the composition of an environmental mixed biofilm in terms of plasmids and antibiotic resistance genes.

A Synergistic Effect of Moringa oleifera-Based Coagulant and Ultrafiltration for the Wastewater Treatment Collected from Final ETP

Provision of safe drinking water, devoid of aetiologies, is an all-time challenge due to the usage of unsafe chemicals in most of the water treatment processes. The main objective of the present paper is to evaluate the use of Moringa oleifera (MO) as a natural coagulant in coagulation/flocculation (C/F) followed by the ultrafiltration (UF) of Final Effluent Treatment Plant wastewater treatment which can also be employed as an alternative to the present conventional methods of treatment. Process efficiency was evaluated in terms of chemical oxygen demand (COD), biochemical oxygen demand (BOD), turbidity, total hardness, alkalinity, ammoniacal nitrogen, and zeta potential along with permeability and fouling behaviour of the membrane. A significant improvement in both the physical and chemical characteristics of the effluent quality is showing a clearer colour and a greater reduction in BOD (89.74%) and COD (63.80%) values, while pH was in the acceptable range for effluent disposal. The results indicate a lower membrane fouling rate (49%), an increase in permeate flow, and better quality of the permeate, proving that the C/F-UF treatment is an effective and efficient technique for wastewater treatment. Eventually, the treated wastewater obtained with this process generates better quality water and preserves the aquatic ecosystem.

Emergence of blaNDM– 1-Carrying Aeromonas caviae K433 Isolated From Patient With Community-Acquired Pneumonia

To demonstrate the detailed genetic characteristics of a bla_NDM–1-carrying multidrug-resistant Aeromonas caviae strain, the complete genome of the A. caviae strain K433 was sequenced by Illumina HiSeq and Oxford nanopore platforms, and mobile genetic elements associated with antibiotic resistance genes were analyzed by a series of bioinformatics methods. A. caviae K433 which was determined to produce class B carbapenemase, was resistant to most antibiotics tested except amikacin. The genome of K433 consisted of a chromosome cK433 (6,482-kb length) and two plasmids: pK433-qnrS (7.212-kb length) and pK433-NDM (200.855-kb length), the last being the first investigated bla_NDM-carrying plasmid from Aeromonas spp. By comparison of the backbone and MDR regions from the plasmids studied, they involved a highly homologous sequence structure. This study provides in-depth genetic insights into the plasmids integrated with bla_NDM-carrying genetic elements from Aeromonas spp.

A comprehensive review on current technologies for removal of endocrine disrupting chemicals from wastewaters

In the recent years, endocrine disrupting compounds (EDCs) has received increasing attention due to their significant toxic effects on human beings and wildlife by affecting their endocrine systems. As an important group of emerging pollutant, EDCs have been detected in various aquatic environments, including surface waters, groundwater, wastewater, runoff, and landfill leachates. Their removal from water resources has also been an emerging concern considering growing population as well as reducing access to fresh water resources. EDC removal from wastewaters is highly dependent on physicochemical properties of the given EDCs present in each wastewater types as well as various aquatic environments. Due to chemical, physical and physicochemical diversities in these parameters, variety of technologies consisting of physical, biological, electrochemical, and chemical processes have been developed for their removal. This review highlights that the effectiveness of EDC removal is highly dependent of selecting the appropriate technology; which decision is made upon a full wastewater chemical characterization. This review aims to provide a comprehensive perspective about all the current technologies used for EDCs removal from various aquatic matrices along with rising challenges such as the antimicrobial resistance gene transfer during EDC treatment.

The High Risk of Bivalve Farming in Coastal Areas With Heavy Metal Pollution and Antibiotic-Resistant Bacteria: A Chilean Perspective

Anthropogenic pollution has a huge impact on the water quality of marine ecosystems. Heavy metals and antibiotics are anthropogenic stressors that have a major effect on the health of the marine organisms. Although heavy metals are also associate with volcanic eruptions, wind erosion or evaporation, most of them come from industrial and urban waste. Such contamination, coupled to the use and subsequent misuse of antimicrobials in aquatic environments, is an important stress factor capable of affecting the marine communities in the ecosystem. Bivalves are important ecological components of the oceanic environments and can bioaccumulate pollutants during their feeding through water filtration, acting as environmental sentinels. However, heavy metals and antibiotics pollution can affect several of their physiologic and immunological processes, including their microbiome. In fact, heavy metals and antibiotics have the potential to select resistance genes in bacteria, including those that are part of the microbiota of bivalves, such as Vibrio spp. Worryingly, antibiotic-resistant phenotypes have been shown to be more tolerant to heavy metals, and vice versa, which probably occurs through co- and cross-resistance pathways. In this regard, a crucial role of heavy metal resistance genes in the spread of mobile element-mediated antibiotic resistance has been suggested. Thus, it might be expected that antibiotic resistance of Vibrio spp. associated with bivalves would be higher in contaminated environments. In this review, we focused on co-occurrence of heavy metal and antibiotic resistance in Vibrio spp. In addition, we explore the Chilean situation with respect to the contaminants described above, focusing on the main bivalves-producing region for human consumption, considering bivalves as potential vehicles of antibiotic resistance genes to humans through the ingestion of contaminated seafood.

Environmental structure impacts microbial composition and secondary metabolism

Determining the drivers of microbial community assembly is a central theme of microbial ecology, and chemical ecologists seek to characterize how secondary metabolites mediate these assembly patterns. Environmental structure affects how communities assemble and what metabolic pathways aid in that assembly. Here, we bridged these two perspectives by addressing the chemical drivers of community assembly within a spatially structured landscape with varying oxygen availability. We hypothesized that structured environments would favor higher microbial diversity and metabolite diversity. We anticipated that the production of a compound would be more advantageous in a structured environment (less mixing) compared to an unstructured environment (more mixing), where the molecule would have a diminished local effect. We observed this to be partially true in our experiments: structured environments had similar microbial diversity compared to unstructured environments but differed significantly in the metabolites produced. We also found that structured environments selected for communities with higher evenness, rather than communities with higher richness. This supports the idea that when characterizing the drivers of community assembly, it matters less about who is there and more about what they are doing. Overall, these data contribute to a growing effort to approach microbial community assembly with interdisciplinary tools and perspectives.

The dietary supplementation of zinc oxide and selenium nanoparticles enhance the immune response in freshwater fish Oreochromis mossambicus against aquatic pathogen Aeromonas hydrophila

BACKGROUND

Green nanoparticles are subjected as an immunostimulant against bacterial pathogens.

METHODS

Murraya koenigii berry extract-based synthesized zinc oxide nanoparticles (Mb-ZnO NPs) and selenium nanoparticles (Mb-Se NPs) were relatively analyzed for immunostimulation in serum and mucus fish Oreochromis mossambicus against Aeromonas hydrophila infections. Initial minimum inhibitory concentration (MIC) was determined for both Mb-ZnO NPs and Mb-Se NPs followed by specific growth rate (SGR), antioxidant level (Superoxide dismutase activity (SOD), Catalase activity (CA), and Glutathione peroxidase activity (GPx)), and immune parameters Myeloperoxidase activity (MPO), Respiratory burst activity (RBA), Lysozyme activity (LYZ), Alkaline phosphatase activity (ALP), Serum antiprotease activity and Natural complement activity (NAC).

RESULTS

The potential bacterial inhibition property of Mb-ZnO NPs and Mb-Se NPs exhibited the most negligible concentration of 25 and 15 μg mL^-1, respectively, against A. hydrophila. In addition, Mb-ZnO NPs and Mb-Se NPs exhibited 70-80 % and 90-95 % diminished biofilm activity at 50 μg mL^-1 that was viewed under an inverted research microscope and confocal laser scanning microscopy (CLSM). Protein leakage and nucleic acid leakage assay quantified oozed out protein and nucleic acid from A. hydrophila that confirms Mb-Se NPs exhibited vigorous antibacterial activity than Mb-ZnO NPs at tested concentrations. Oreochromis mossambicus fed with Mb-ZnO NPs and Mb-Se NPs supplemented diet at different concentrations (0.5 mg/kg, 1 mg/kg and 2 mg/kg) improved SGR along with a rise in the immune response of those fishes against A. hydrophila infection. Serum and mucus of fish fed with Mb-Se NPs supplemented diet exhibited a significant rise in antioxidant level SOD, CA and GPx at a dosage of 2 mg/kg. Likewise, lipid peroxidation assay detected significantly diminished oxidative stress in the serum and mucus of fish fed with Mb-Se NPs supplemented diet (2 mg/kg). Enhanced immune parameters in serum and mucus of fish fed with Mb-Se NPs supplemented diet determined by MPO, RBA, LYZ, ALP, Serum antiprotease activity and NAC.

CONCLUSION

Thus O. mossambicus fed with Mb-Se NPs supplemented diet was less prone to become infected by aquatic pathogen A. hydrophila established by challenge study. On the whole, Mb-Se NPs supplemented diet ensured the rise in antioxidant response that boosts the immune responses and reduces the chance of getting infected against A. hydrophila infections.

Controlling pathogenic risks of water treatment biotechnologies at the source by genetic editing means

Antimicrobial-resistant pathogens in the environment and wastewater treatment systems, many of which are also important pollutant degraders and are difficult to control by traditional disinfection approaches, have become an unprecedented treat to ecological security and human health. Here, we propose the adoption of genetic editing techniques as a highly targeted, efficient and simple tool to control the risks of environmental pathogens at the source. An 'all-in-one' plasmid system was constructed in Aeromonas hydrophila to accurately identify and selectively inactivate multiple key virulence factor genes and antibiotic resistance genes via base editing, enabling significantly suppressed bacterial virulence and resistance without impairing their normal phenotype and pollutant-degradation functions. Its safe application for bioaugmented treatment of synthetic textile wastewater was also demonstrated. This genetic-editing technique may offer a promising solution to control the health risks of environmental microorganisms via targeted gene inactivation, thereby facilitating safer application of water treatment biotechnologies.

Mobility of antibiotic resistance and its co-occurrence with metal resistance in pathogens under oxidative stress

The bacterial communities are challenged with oxidative stress during their exposure to bactericidal antibiotics, metals, and different levels of dissolved oxygen (DO) encountered in diverse environmental habitats. The frequency of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) co-selection is increased by selective pressure posed by oxidative stress. Hence, study of resistance acquisition is important from an evolutionary perspective. To understand the dependence of oxidative stress on the dissemination of ARGs and MRGs through a pathogenic bacterial population, 12 metagenomes belonging to gut, water and soil habitats were evaluated. The metagenome-wide analysis showed the chicken gut to pose the most diverse pool of ARGs (30.4 ppm) and pathogenic bacteria (Simpson diversity = 0.98). The most common types of resistances found in all the environmental samples were efflux pumps (13.22 ppm) and genes conferring resistance to vancomycin (12.4 ppm), tetracycline (12.1 ppm), or beta-lactam (9.4 ppm) antibiotics. Additionally, limiting DO level in soil was observed to increase the abundance of excision nucleases (uvrA and uvrB), DNA polymerase (polA), catalases (katG), and other oxidative stress response genes (OSGs). This was further evident from major variations occurred in antibiotic efflux genes due to the effect of DO concentration on two human pathogens, namely Salmonella enterica and Shigella sonnei found in all the selected habitats. In conclusion, the microbial community, when challenged with oxidative stress caused by environmental variations in oxygen level, tends to accumulate higher amounts of ARGs with increased dissemination potential through triggering non-lethal mutagenesis. Furthermore, the genetic linkage or co-occurrence of ARGs and MRGs provides evidence for selecting ARGs under high concentrations of heavy metals.

A Review on Occurrence and Spread of Antibiotic Resistance in Wastewaters and in Wastewater Treatment Plants: Mechanisms and Perspectives

This paper reviews current knowledge on sources, spread and removal mechanisms of antibiotic resistance genes (ARGs) in microbial communities of wastewaters, treatment plants and downstream recipients. Antibiotic is the most important tool to cure bacterial infections in humans and animals. The over- and misuse of antibiotics have played a major role in the development, spread, and prevalence of antibiotic resistance (AR) in the microbiomes of humans and animals, and microbial ecosystems worldwide. AR can be transferred and spread amongst bacteria via intra- and interspecies horizontal gene transfer (HGT). Wastewater treatment plants (WWTPs) receive wastewater containing an enormous variety of pollutants, including antibiotics, and chemicals from different sources. They contain large and diverse communities of microorganisms and provide a favorable environment for the spread and reproduction of AR. Existing WWTPs are not designed to remove micropollutants, antibiotic resistant bacteria (ARB) and ARGs, which therefore remain present in the effluent. Studies have shown that raw and treated wastewaters carry a higher amount of ARB in comparison to surface water, and such reports have led to further studies on more advanced treatment processes. This review summarizes what is known about AR removal efficiencies of different wastewater treatment methods, and it shows the variations among different methods. Results vary, but the trend is that conventional activated sludge treatment, with aerobic and/or anaerobic reactors alone or in series, followed by advanced post treatment methods like UV, ozonation, and oxidation removes considerably more ARGs and ARB than activated sludge treatment alone. In addition to AR levels in treated wastewater, it examines AR levels in biosolids, settled by-product from wastewater treatment, and discusses AR removal efficiency of different biosolids treatment procedures. Finally, it puts forward key-points and suggestions for dealing with and preventing further increase of AR in WWTPs and other aquatic environments, together with a discussion on the use of mathematical models to quantify and simulate the spread of ARGs in WWTPs. Mathematical models already play a role in the analysis and development of WWTPs, but they do not consider AR and challenges remain before models can be used to reliably study the dynamics and reduction of AR in such systems.

Virulence and Antimicrobial Resistance Pattern of Aeromonas spp. Colonizing European Pond Turtles Emys orbicularis and Their Natural Environment. First Study from Poland

The aim of the study was to isolate and identify species belonging to the Aeromonas genus and evaluate the antimicrobial resistance and virulence patterns of isolates colonizing European pond turtles (Emys orbicularis) from natural environment of Eastern Poland. In total, 74 turtles and 15 samples of water from their natural environment were examined. More than 40 strains were isolated and identified: A. bestiarum (n = 1), A. hydrophila (n = 13), A. allosaccharophila (n = 2), A. salmonicida (n = 3), and A. veronii (n = 23). The highest incidence of resistance was noted for ampicillin (100%) and sulfamethoxazole (62.0%), followed by erythromycin and colistin (both 40.5%). Moreover, eight strains were intermediately resistant to meropenem (19%). Most Aeromonas isolates were found to possess more than one virulence gene among fla, aer, hlyA, act, ela, alt, and ast. We showed that the population of free-living European pond turtles was highly colonized by Aeromonas spp. Such strains may be an infectious agent not only for the population of turtles but also for other species of animals inhabiting their natural environment. Moreover, the undesirable properties of water quality caused by the presence of drug-resistant aeromonads could have a negative impact on human health.

Enhanced photocatalytic performance of PdO-loaded heterostructured nanobelts to degrade phenol

Heterostructured catalysts play a significant role in the photodegradation of pollutants in wastewater. Combining the large surface of nanobelts with the high photocatalytic property of titanium dioxide (TiO₂) nanoparticles is a promising method for preparing photocatalysts, which have an advanced photocatalytic activity and are easy to precipitate. In this work, titanium dioxide nanobelts (NB) and acid corroded titanium dioxide nanobelts (C-NB) were synthesized via a hydrothermal process under alkaline conditions. Their surfaces were then loaded with palladium oxide (PdO) nanoparticles to prepare heterostructured photocatalysts (PdO-NB and PdO-C-NB) by a well-designed chemical precipitation method. The photodegradation efficiencies of the four catalysts for phenol, as well as for methyl orange, were tested and the order of degradation efficiency was found to be PdO-C-NB > PdO-NB > C-NB > NB. A degradation efficiency of 61% for phenol was achieved within 90 min using PdO-C-NB, which was nearly twice as much as using NB. The enhanced photocatalytic property of PdO-C-NB was due to the large specific surface area, abundant photocatalytic active sites and the low recombination rate of electron-hole pairs. Therefore, the degradation of phenol and methyl orange was speeded up considerably. Considering the high catalytic activity of PdO-C-NB, the heterostructure catalyst is of great significance to the degradation of organic wastewater, and has an important impact on our ecological environment and human health.

Coming from the Wild: Multidrug Resistant Opportunistic Pathogens Presenting a Primary, Not Human-Linked, Environmental Habitat

The use and misuse of antibiotics have made antibiotic-resistant bacteria widespread nowadays, constituting one of the most relevant challenges for human health at present. Among these bacteria, opportunistic pathogens with an environmental, non-clinical, primary habitat stand as an increasing matter of concern at hospitals. These organisms usually present low susceptibility to antibiotics currently used for therapy. They are also proficient in acquiring increased resistance levels, a situation that limits the therapeutic options for treating the infections they cause. In this article, we analyse the most predominant opportunistic pathogens with an environmental origin, focusing on the mechanisms of antibiotic resistance they present. Further, we discuss the functions, beyond antibiotic resistance, that these determinants may have in the natural ecosystems that these bacteria usually colonize. Given the capacity of these organisms for colonizing different habitats, from clinical settings to natural environments, and for infecting different hosts, from plants to humans, deciphering their population structure, their mechanisms of resistance and the role that these mechanisms may play in natural ecosystems is of relevance for understanding the dissemination of antibiotic resistance under a One-Health point of view.

Metallo-β-lactamases in the Age of Multidrug Resistance: From Structure and Mechanism to Evolution, Dissemination, and Inhibitor Design

Antimicrobial resistance is one of the major problems in current practical medicine. The spread of genes coding for resistance determinants among bacteria challenges the use of approved antibiotics, narrowing the options for treatment. Resistance to carbapenems, last resort antibiotics, is a major concern. Metallo-β-lactamases (MBLs) hydrolyze carbapenems, penicillins, and cephalosporins, becoming central to this problem. These enzymes diverge with respect to serine-β-lactamases by exhibiting a different fold, active site, and catalytic features. Elucidating their catalytic mechanism has been a big challenge in the field that has limited the development of useful inhibitors. This review covers exhaustively the details of the active-site chemistries, the diversity of MBL alleles, the catalytic mechanism against different substrates, and how this information has helped developing inhibitors. We also discuss here different aspects critical to understand the success of MBLs in conferring resistance: the molecular determinants of their dissemination, their cell physiology, from the biogenesis to the processing involved in the transit to the periplasm, and the uptake of the Zn(II) ions upon metal starvation conditions, such as those encountered during an infection. In this regard, the chemical, biochemical and microbiological aspects provide an integrative view of the current knowledge of MBLs.

Identification, antibiotic resistance, and virulence profiling of Aeromonas and Pseudomonas species from wastewater and surface water

Aquatic environments are hotspots for the spread of antibiotic-resistant bacteria and genes due to pollution caused mainly by anthropogenic activities. The aim of this study was to evaluate the impact of wastewater effluents, informal settlements, hospital, and veterinary clinic discharges on the occurrence, antibiotic resistance profile and virulence signatures of Aeromonas spp. and Pseudomonas spp. isolated from surface water and wastewater. High counts of Aeromonas spp. (2.5 (± 0.8) - 3.3 (± 0.4) log₁₀ CFU mL^-1) and Pseudomonas spp. (0.6 (± 1.0) - 1.8 (± 1.0) log₁₀ CFU mL^-1) were obtained. Polymerase chain reaction (PCR) and MALDI-TOF characterization identified four species of Aeromonas and five of Pseudomonas. The isolates displayed resistance to 3 or more antibiotics (71% of Aeromonas and 94% of Pseudomonas). Aeromonas spp. showed significant association with the antibiotic meropenem (χ² = 3.993, P < 0.05). The virulence gene aer in Aeromonas was found to be positively associated with the antibiotic resistance gene blaOXA (χ² = 6.657, P < 0.05) and the antibiotic ceftazidime (χ² = 7.537, P < 0.05). Aeromonas recovered from both wastewater and surface water displayed high resistance to ampicillin and had higher multiple antibiotic resistance (MAR) indices close to the hospital. Pseudomonas isolates on the other hand exhibited low resistance to carbapenems but very high resistance to the third-generation cephalosporins and cefixime. The results showed that some of the Pseudomonas spp. and Aeromonas spp. isolates were extended-spectrum β-lactamase producing bacteria. In conclusion, the strong association between virulence genes and antibiotic resistance in the isolates shows the potential health risk to communities through direct and indirect exposure to the water.

The Role of Aquatic Ecosystems (River Tua, Portugal) as Reservoirs of Multidrug-Resistant Aeromonas spp

The inappropriate use of antibiotics, one of the causes of the high incidence of antimicrobial-resistant bacteria isolated from aquatic ecosystems, represents a risk for aquatic organisms and the welfare of humans. This study aimed to determine the antimicrobial resistance rates among riverine Aeromonas spp., taken as representative of the autochthonous microbiota, to evaluate the level of antibacterial resistance in the Tua River (Douro basin). The prevalence and degree of antibiotic resistance was examined using motile aeromonads as a potential indicator of antimicrobial susceptibility for the aquatic environment. Water samples were collected from the middle sector of the river, which is most impacted area by several anthropogenic pressures. Water samples were plated on an Aeromonas-selective agar, with and without antibiotics. The activity of 19 antibiotics was studied against 30 isolates of Aeromonas spp. using the standard agar dilution susceptibility test. Antibiotic resistance rates were fosfomycin (FOS) 83.33%, nalidixic acid (NA) 60%, cefotaxime (CTX) 40%, gentamicin (CN) 26.67%, tobramycin (TOB) 26.67%, cotrimoxazole (SXT) 26.67%, chloramphenicol (C) 16.67%, and tetracycline (TE) 13.33%. Some of the nalidixic acid-resistant strains were susceptible to fluoroquinolones. Multiple resistance was also observed (83.33%). The environmental ubiquity, the natural susceptibility to antimicrobials and the zoonotic potential of Aeromonas spp. make them optimal candidates for studying antimicrobial resistance (AMR) in aquatic ecosystems. Aquatic environments may provide an ideal setting for the acquisition and dissemination of antibiotic resistance because anthropogenic activities frequently impact them. The potential risk of multi- and pan-resistant bacteria transmission between animals and humans should be considered in a “One Health—One World” concept.

Detection of multi-drug resistance and AmpC β-lactamase/extended-spectrum β-lactamase genes in bacterial isolates of loggerhead sea turtles (Caretta caretta) from the Mediterranean Sea

Sea turtles are useful sentinels to monitor the dissemination of antimicrobial resistance (AMR) in the marine coastal ecosystems. Forty Gram negative bacteria were isolated from wounds of 52 injured Caretta caretta, living in the Mediterranean Sea. Bacteria were identified using 16S rRNA gene sequencing and tested for susceptibility to 15 antibiotics. In addition, NGS amplicon sequencing was performed to detect the presence of AmpC β-lactamase genes (bla_AmpC) and extended-spectrum β-lactamase (ESBL) genes (bla_CTX-M,bla_SHV,bla_TEM). Seventy-five percent of the isolates (30/40 isolates) exhibited multidrug resistance (MDR) phenotypes and 32.5% (13/40 isolates) were confirmed to be positive for at least one gene. The variants of ESBLs genes were bla_CTX-M-3,bla_TEM-236 and bla_SHV-12. Variants of the bla_AmpCβ-lactamase gene i.e., bla_ACT-24, bla_ACT-2, bla_ACT-17, bla_DHA-4 and bla_CMY-37, were also detected. In addition, 4 isolates were found simultaneously harboring CTX and AmpC genes while 2 strains harbored 3 genes (bla_{ACT-2+TEM-236+SHV-12}, and bla_{CTX-M-3+ACT-24+TEM-236}).

Dependence of arsenic resistance and reduction capacity of Aeromonas hydrophila on carbon substrate

The high toxicity and prevalence of arsenic in the environment have aroused increasing research interest in understanding the mechanisms of microbial arsenic resistance. A wide spectrum of arsenic resistant microbes with ability of arsenic bio-transformation has been isolated from arsenic-contaminated environments. However, arsenic resistance processes and reduction abilities of microbes under various growth conditions remain poorly understood. In this work, a high correlation between the arsenic resistance and reduction ability of Aeromonas hydrophila and the carbon substrate was identified. Genome analysis suggests that the arsenic resistance system is widely present in Aeromonas genus, and the arsenic resistance was associated with the ars operon. The sensitivity of A. hydrophila to As(V) and As(III) depended heavily on the type of carbon substrate. The upregulated expression of arsA, arsB, arsD and/or downregulated expression of glpF might be responsible for the increased microbial tolerance to As(III). The As(V) reduction rate was also affected by the type of carbon substrate. Our results provide new insights into the impacts of carbon substrate on the arsenic biotoxicity as well as arsenic biotransformation processes.

Detection of carbapenem-resistance genes in bacteria isolated from wastewater in Ontario

Bacterial carbapenem resistance is a major public health concern since these antimicrobials are often the last resort to treat serious human infections. To evaluate methodologies for detection of carbapenem resistance, carbapenem-tolerant bacteria were isolated from wastewater treatment plants in Toronto, Ottawa, and Arnprior, Ontario. A total of 135 carbapenem-tolerant bacteria were recovered. Polymerase chain reaction (PCR) indicated the presence of carbapenem hydrolysing enzymes KPC ( n = 10), GES ( n = 5), VIM ( n = 7), and IMP ( n = 1), and β-lactamases TEM ( n = 7), PER ( n = 1), and OXA-variants ( n = 16). A subset of 46 isolates were sequenced and analysed using ResFinder and CARD-RGI. Both programs detected carbapenem resistance genes in 35 sequenced isolates and antimicrobial resistance genes (ARGs) conferring resistance to multiple class of other antibiotics. Where β-lactamase resistance genes were not initially identified, lowering the thresholds for ARG detection enabled identification of closely related β-lactamases. However, no known carbapenem resistance genes were found in seven sequenced Pseudomonas spp. isolates. Also of note was a multi-drug-resistant Klebsiella pneumoniae isolate from Ottawa, which harboured resistance to seven antimicrobial classes including β-lactams. These results highlight the diversity of genes encoding carbapenem resistance in Ontario and the utility of whole genome sequencing over PCR for ARG detection where resistance may result from an assortment of genes.

Antimicrobial resistance in Aeromonas species isolated from aquatic environments in Brazil

AIM

The current study was conducted to determine the antimicrobial resistance profile and genetic relatedness of Aeromonas sp. isolated from healthcare and urban effluents, wastewater treatment plant (WWTP) and river water.

METHODS AND RESULTS

We detected the presence of genes conferring resistance to β-lactam, quinolone and aminoglycoside. Multilocus sequence typing was carried out to differentiate the strains, and multilocus phylogenetic analysis was used to identify the species. A total of 28 cefotaxime-resistant Aeromonas sp. strains were identified, harbouring uncommon Guiana-extended-spectrum (GES)-type β-lactamases (GES-1, GES-5, GES-7 and GES-16). Multidrug-resistant Aeromonas sp. were found in hospital wastewater, WWTP and sanitary effluent, and A. caviae was identified as the most prevalent species (85·7%).

CONCLUSION

The release of untreated healthcare effluents, presence of antimicrobials in the environment, in addition to multidrug-resistant Aeromonas sp., are all potential factors for the spread of resistance.

SIGNIFICANCE AND IMPACT OF THE STUDY

We identified a vast repertoire of antimicrobial resistance genes (ARG) in Aeromonas sp. from diverse aquatic ecosystems, including those that encode enzymes degrading broad-spectrum antimicrobials widely used to treat healthcare-associated infections. Hospital and sanitary effluents serve as potential sources of bacteria harbouring ARG and are a threat to public health.

Recent Insights into Aeromonas salmonicida and Its Bacteriophages in Aquaculture: A Comprehensive Review

The emergence and spread of antimicrobial resistance in pathogenic bacteria of fish and shellfish have caused serious concerns in the aquaculture industry, owing to the potential health risks to humans and animals. Among these bacteria, Aeromonas salmonicida, which is one of the most important primary pathogens in salmonids, is responsible for significant economic losses in the global aquaculture industry, especially in salmonid farming because of its severe infectivity and acquisition of antimicrobial resistance. Therefore, interest in the use of alternative approaches to prevent and control A. salmonicida infections has increased in recent years, and several applications of bacteriophages (phages) have provided promising results. For several decades, A. salmonicida and phages infecting this fish pathogen have been thoroughly investigated in various research areas including aquaculture. The general overview of phage usage to control bacterial diseases in aquaculture, including the general advantages of this strategy, has been clearly described in previous reviews. Therefore, this review specifically focuses on providing insights into the phages infecting A. salmonicida, from basic research to biotechnological application in aquaculture, as well as recent advances in the study of A. salmonicida.

Spatiotemporal Changes of Antibiotic Resistance and Bacterial Communities in Drinking Water Distribution System in Wrocław, Poland

Antibiotic resistance of bacteria is an emerging problem in drinking water treatment. This paper presents the comparison of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) prevalence during the summer and winter season in a full-scale drinking water distribution system (DWDS) supplied by two water treatment plants (WTPs). The effect of distance from WTP and physical–chemical water parameters on its microbial properties was also tested. Bacterial consortia dwelling in bulk tap water were additionally compared by means of denaturating gradient gel electrophoresis (DGGE). The results showed that among ARB, bacteria resistant to ceftazidime (CAZ) were the most abundant, followed by bacteria resistant to amoxicillin (AML), ciprofloxacin (CIP), and tetracycline (TE). Numerous ARGs were detected in tested tap water samples. Only CAZ resistant bacteria were more prevalent in the season of increased antibiotic consumption, and only AML resistant bacteria relative abundances increase was statistically significant with the distance from a WTP. The investigated tap water meets all legal requirements. It is therefore safe to drink according to the law. Nevertheless, because antibiotic resistance could pose a threat to consumer health, it should be further monitored in DWDSs.

The determination of antimicrobial susceptibility by MIC and epidemiological cut-off values and the detection of resistance genes in Aeromonas species isolated from cultured fish

The present study was aimed at determining antimicrobial susceptibility by a CLSI standard microdilution testing protocol and detecting the resistance genes of motile Aeromonas species isolated from cultured fish. The importance of the minimum inhibitory concentrations was assessed based on statistically determined epidemiological cut-off values calculated by normalized resistance analysis. Unfortunately, CLSI epidemiological cut-off values are available only for Aeromonas salmonicida, and there is no further detailed data on Aeromonas isolated from aquatic animals. The antimicrobial susceptibilities of pre-identified motile Aeromonas species to florfenicol, tetracycline and sulfamethoxazole were determined by calculating epidemiological cut-off values with fully automated and freely available Excel spreadsheets, applying the normalized resistance interpretation (NRI) method. Furthermore, the presence of the antimicrobial resistance genes floR, tetA, tetB, tetC, tetD, tetE, tetH, sulI, sulII and sulIII was detected by PCR analysis and confirmed by sequence analysis. The presence of up to six different genes (multiple antimicrobial resistance) was determined in the Aeromonas isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: Significance and Impact of the Study: In this study, we investigated phenotypic and genotypic antimicrobial resistance characteristics by a novel method based on epidemiological cut-off values. This is the second comprehensive study on the antimicrobial susceptibility characteristics of Aeromonas species using NRI and epidemiological cut-off values. The present research is related to our previous researches focussed on the identification of motile Aeromonads, their prevalence in relation to different fish lengths, seasons and regions, and covered the investigation of Lactococcus garvieae, Yersinia ruckeri, Flavobacterium spp., Enterobacter spp. and Citrobacter spp.