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• Published: 15 March 2024

Metagenomic insights into the wastewater resistome before and after purification at large‑scale wastewater treatment plants in the Moscow city

• Shahjahon Begmatov 1 ,
• Alexey V. Beletsky 1 ,
• Alexander G. Dorofeev 2 ,
• Nikolai V. Pimenov 2 ,
• Andrey V. Mardanov 1 &
• Nikolai V. Ravin 1  

Scientific Reports volume  14 , Article number:  6349 ( 2024 ) Cite this article

796 Accesses

Metrics details

• Antimicrobials
• Microbial communities
• Industrial microbiology

Wastewater treatment plants (WWTPs) are considered to be hotspots for the spread of antibiotic resistance genes (ARGs). We performed a metagenomic analysis of the raw wastewater, activated sludge and treated wastewater from two large WWTPs responsible for the treatment of urban wastewater in Moscow, Russia. In untreated wastewater, several hundred ARGs that could confer resistance to most commonly used classes of antibiotics were found. WWTPs employed a nitrification/denitrification or an anaerobic/anoxic/oxic process and enabled efficient removal of organic matter, nitrogen and phosphorus, as well as fecal microbiota. The resistome constituted about 0.05% of the whole metagenome, and after water treatment its share decreased by 3–4 times. The resistomes were dominated by ARGs encoding resistance to beta-lactams, macrolides, aminoglycosides, tetracyclines, quaternary ammonium compounds, and sulfonamides. ARGs for macrolides and tetracyclines were removed more efficiently than beta-lactamases, especially ampC , the most abundant ARG in the treated effluent. The removal efficiency of particular ARGs was impacted by the treatment technology. Metagenome-assembled genomes of multidrug-resistant strains were assembled both for the influent and the treated effluent. Ccomparison of resistomes from WWTPs in Moscow and around the world suggested that the abundance and content of ARGs depend on social, economic, medical, and environmental factors.

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Introduction.

The spread of antimicrobial resistance (AMR) in the environmental microbiome has become one of the frequently noted problems in recent years, along with global climate change, food security and other technological challenges. Numerous studies show that from year to year, in addition to increasing the cost of hospitalization and treatment of patients infected with multidrug-resistant bacteria, the number of deaths of such patients is growing 1 , 2 . Understanding the mechanisms underlying the emergence, selection and dissemination of AMR, and antibiotic resistance genes (ARGs), is required for the development of sustainable strategies to control and minimize this threat. The dissemination of antibiotic resistant bacteria (ARB) and ARGs occurs differently and this process is more active in urban territories rather than in rural ones. The rate of spread of ARGs and ARB in urban areas is obviously determined by the high population density and, as a rule, wastewater which flows from these areas contains both ARG and ARB. Most antibiotics used in medicine, agriculture and the food industry, as well as resistant bacteria, end up in wastewater. Wastewater treatment plants (WWTPs) therefore could provide a comprehensive overview of ARG abundance, diversity and genomic backgrounds in particular region 3 . Moreover, wastewater and WWTPs are places where ARGs and ARB are particularly abundant and are often considered “hotspots” for the formation of strains with multiple resistance and one of the main sources of the spread of AMR in the environment 4 .

Despite numerous studies on the role of WWTPs in resistome diversity and dissemination, each new study is, in terms of time and geography, unique, as many urban areas and countries have not yet been studied. In addition, some studies are dedicated to explore only one component of the wastewater treatment system, such as wastewater, activated sludge or treated effluent, and there is a lack of research that would give a comprehensive view of the diversity and change in the composition of the resistome at different stages of water cleaning, from wastewater to treated effluent, released into the environment.

Usually, wastewater treatment in large facilities takes place in three stages. The first stage includes physical methods of water cleaning, the second stage is microbiological treatment in bioreactors with activated sludge (AS), and the third stage is the final treatment of water and its disinfection. At the second stage, than could be performed using several technologies, microorganisms of AS are used to remove organic matter, ammonium, and (in more complex processes) phosphorus 5 . At this stage, the removal of microorganisms present in the wastewater, including ARB, occurs due to their adsorption on AS particles, which are removed along with excess AS. The efficiency of this process differs for various bacteria and depends on the purification technology used. Therefore, purification technologies directly affect the removal of particular ARGs and ARB, however, this issue was poorly studied 6 .

ARGs representing all known resistance mechanisms have been found in WWTP environments 7 . ARGs for beta-lactams, macrolides, quinolones, tetracyclines, sulfonamides, trimethoprim, and multidrug efflux pump genes have been found in the incoming wastewater, AS, and treated effluent in various countries 7 , 8 . Recently, Munk and coauthors (2022) using metagenomics methods characterized resistomes of 757 urban wastewater samples from 243 cities in 101 countries covering 7 major geographical regions. They reported regional patterns in wastewater resistomes that differed between subsets corresponding to drug classes and were partly driven by taxonomic variation 3 . Although this study did not analyzes the composition of the wastewater resistome after treatment, there are numerous evidences that the prevalence of ARB and ARG in rivers may increase downstream from the point of discharge of treated wastewater into them 9 , 10 . In a study of WWTPs in Germany, 123 types of clinically significant antibiotic resistance genes were found in treated wastewater discharged into water bodies 11 . An analysis of the presence of 30 ARGs at different stages of wastewater treatment at WWTPs in Northern China showed that the content of most ARGs in the treated effluent was lower compared to the influent entering the treatment, although an increase in the abundance of some ARGs and their release into the environment was also observed 12 . A metagenomic analysis of WWTP in Hong Kong revealed seasonal changes in the content of several types of ARG and its decrease in the treated effluent 13 , 14 . Most ARGs were reduced by more than 98% in the treated effluent compared to the wastewater entering the treatment 14 . Some other studies have also reported a decrease in ARGs after wastewater treatment 15 , 16 , 17 . However, in other studies, no changes in the ARG content or even an increase were observed 17 , 18 , 19 . Although there are numerous studies of resistomes in WWTP-related environments the distribution of samples was geographically biased and covered mostly North America, Western Europe, Eastern Asia (mostly China), Australasia, and few places in South America/Caribbean and Sub-Saharan Africa 3 .

In order to expand the geographical coverage and our knowledge about global resistome abundance and diversity, we analyzed resistomes of wastewater before and after treatment at large-scale WWTPs in the city of Moscow (Russia). Although Moscow WWTPs are among the largest in the world and may play an important role in the spread of antibiotic resistance, the resistomes of municipal wastewaters in Moscow have not previously been studied by modern molecular genetic methods. Previously we performed 16S rRNA gene profiling of AS microbial communities at large-scale WWTPs responsible for the treatment of municipal wastewater ion Moscow 5 . Comparison of microbial communities of AS samples from WWTPs in Moscow and worldwide revealed that Moscow samples clustered together indicating the importance of influent characteristics, related to local social and environmental factors, for wastewater microbiomes 5 . For example, due to the relatively low cost of water for household consumption, wastewater in Moscow has a relatively low content of organic matter. Apparently the presence of ARB and ARGs in communal wastewater depends on the frequency of antibiotic use and the range of drugs used. These factors differ in different countries and cities. Therefore, the characterization of the resistome and the role of Moscow WWTPs in the dispersion of ARGs is an important goal. Of particular interest is also the assessment of the impact of wastewater treatment technology on the composition of the resistome and the degree of ARG removal.

Here we present the first metagenomic overview of the composition of resistome of influent wastewater, AS and treated effluent released into the environment at two Moscow WWTPs employing different treatment technologies.

Characteristics of WWTPs and water chemistry

The Lyuberetskiy WWTP complex of JSC “Mosvodokanal” carry out the treatment of wastewater in the city of Moscow with a capacity of about 2 million m 3 per day. This complex consists of several wastewater treatment units (hereafter referred to as WWTPs). They purify the same inflow wastewater but otherwise are independent installations between which there is no transfer and mixing of AS. Two WWTPs implementing different technologies for wastewater treatment were chosen as the objects of study. The first one (LOS) is operated using anaerobic/anoxic/oxic process, also known as the University of Cape Town (UCT) technology. There the sludge mixture first enters the anaerobic zone, where phosphate-accumulating microorganisms (PAO) consume easily degradable organics, then to the anoxic zone, where denitrification and accumulation of phosphates by denitrifying PAO occur, and finally to the aerobic zone, where organic matter and ammonium are oxidized while PAO accumulate large quantities of polyphosphate. The second WWTP (NLOS2) uses a simpler nitrification–denitrification technology (N-DN). In the aerobic zones organics and ammonium are oxidized, while in the anoxic zone nitrate is reduced to gaseous nitrogen. This treatment technology removes organic matter and nitrogen, but was not specially aimed to remove phosphates. The production capacity of LOS is approximately 2 times more than that of NLOS2; there are no other important differences between these WWTPs besides treatment technology.

Sampling and chemical analysis

Wastewater and AS samples were collected in September 2022 and kindly provided by “Mosvodokanal” JSC. The temperature of water samples was about 24 °C. Samples of AS from bioreactors of two WWTPs were taken in 50 ml Falcon tubes (BD Biosciences). Wastewater samples (influent and effluents from two WWTPs) were taken in 5 L plastic bottles. The cells were collected by centrifugation at 3000 g for 20 min at 4 °C.

Wastewater quality values, namely, biochemical oxygen demand (five days incubation) (BOD 5 ), chemical oxygen demand (COD), total suspended solids (TSS), sludge volume index (SVI), ammonium nitrogen (N-NH 4 ), nitrate nitrogen (N-NO 3 ), nitrite nitrogen (N-NO 2 ) and phosphorus (P-PO 4 ) in the influent and effluents of two WWTPs were measured by the specialized laboratory “MSULab” according to the Federal inspection of environmental management’s protocols for chemical analyses of water.

DNA isolation, 16S rRNA gene sequencing and analysis

Total genomic DNA was isolated using a Power Soil DNA isolation kit (Qiagen, Germany). DNA for each sample was isolated in four parallel replicates, which were then pooled. PCR amplification of 16S rRNA gene fragments comprising the V3–V4 variable regions was performed using the universal primers 341F (5′-CCTAYG GGDBGCWSCAG) and 806R (5′-GGA CTA CNVGGG THTCTAAT) 20 . The obtained PCR fragments were bar-coded and sequenced on Illumina MiSeq (2 × 300 nt reads). Pairwise overlapping reads were merged using FLASH v.1.2.11 21 . All sequences were clustered into operational taxonomic units (OTUs) at 97% identity using the USEARCH v.11 program 22 . Low quality reads were removed prior to clustering, chimeric sequences and singletons were removed during clustering by the USEARCH algorithms. To calculate OTU abundances, all reads obtained for a given sample were mapped to OTU sequences at a 97% global identity threshold by USEARCH. The taxonomic assignment of OTUs was performed by searching against the SILVA v.138 rRNA sequence database using the VSEARCH v. 2.14.1 algorithm 23 .

The diversity indices at a 97% OTU cut-off level were calculated using USEARCH v.11 22 . To avoid sequencing depth bias, the numbers of reads for each sample were randomly sub-sampled to the size of the smallest set.

Sequencing of metagenomic DNA, contigs assembly and binning of MAGs

Metagenomic DNA was sequenced using the Illumina HiSeq2500 platform according to the manufacturer’s instructions (Illumina Inc., San Diego, CA, USA). The sequencing of a paired-end (2 × 150 bp) NEBNext Ultra II DNA Library prep kit (NEB) generated from 145 to 257 million read pairs per sample. Adapter removal and trimming of low-quality sequences (Q < 30) were performed using Cutadapt v.3.4 24 and Sickle v.1.33 ( https://github.com/najoshi/sickle ), respectively. The resulting Illumina reads were de novo assembled into contigs using SPAdes v.3.15.4 in metagenomic mode 25 .

The obtained contigs were binned into metagenome-assembled genomes (MAGs) using 3 different programs: MetaBAT v.2.2.15 26 , MaxBin v.2.2.7 27 and CONCOCT v.1.1.0 28 . The results of the three binning programs were merged into an optimized set of MAGs using DAS Tool v.1.1.4 29 . The completeness of the MAGs and their possible contamination (redundancy) were estimated using CheckM v.1.1.3 30 with lineage-specific marker genes. The assembled MAGs were taxonomically classified using the Genome Taxonomy Database Toolkit (GTDB-Tk) v.2.0.0 31 and Genome Taxonomy database (GTDB) 32 .

ARG identification

Open reading frames (ORFs) were predicted in assembled contigs using Prodigal v.2.6.3 33 . ARGs were predicted using the NCBI AMRFinderPlus v.3.11.4 ( https://github.com/ncbi/amr/wiki ) command line tool and its associated database 34 . The predicted protein sequences of all ORFs were analyzed in this tool with parameter “-p”.

Efficiency of wastewater treatment

Two wastewater treatment technologies were used in the investigated WWTPs,—nitrification/denitrification at NLOS2 and more advanced anaerobic/anoxic/oxic UCT process at LOS. LOS removed more than 99.5% of organic matter (according to the BOD5 data) and more than 99.9% of ammonium while the performance of NLOS2 was poorer (Table 1 ). Particularly noticeable differences were observed in nitrate and nitrite concentrations in the effluents suggesting the lower efficiency of denitrification in the NLOS2. Interestingly, although the NLOS2 unit was not designed to remove phosphorus, the concentration of phosphates in the treated effluent at this WWTP is only slightly higher than at LOS. The treated influent at LOS contains fewer solids consistently with lower SVI. Overall, the technology used at LOS plant is more efficient.

Microbiomes of the influent wastewater, activated sludge and treated effluent

The 16S rRNA gene profiling of microbial communities revealed 1013 species-level OTUs (97% identity) in the influent and 1.2–1.7 times more OTUs in the AS and treated effluent samples (Supplemental Table S1 ). The Shannon diversity indices correlated with the number of detected OTUs and increased in the series “influent” – “activated sludge” – “effluent” at each WWTP (Supplemental Table S2 ).

Analysis of the microbiome of wastewater supplied for biological treatment showed that that the most numerous phyla in the microbial community were Firmicutes (28.4% of all 16S rRNA gene sequences), Campylobacterota (28.0%), Proteobacteria (20.9%), and Bacteroidota (10.5%) (Fig.  1 ). These were mainly representatives of the fecal microbiota, which are often found in wastewater. The phylum Firmicutes was dominated by Streptococcaceae (9.7%, mostly S treptococcus sp.), Lachnospiraceae (5.9%), Ruminococcaceae (3.0%), Carnobacteriaceae (1.7%), Peptostreptococcaceae (1.6%) and Veillonellaceae (1.4%). Most of Campylobacterota belonged to the family Arcobacteraceae (26.8%) of the genera Arcobacter (19.9%), Pseudarcobacter (2.5%) and uncultured lineage (4.3%), as well as by sulfur-oxidizing Sulfurospirillum (1.0%). Among the Proteobacteria the most abundant genera were Acinetobacter (7.8%) , Aeromonas (1.8%) and Pseudomonas (1.1%). Most of the identified Bacteroidota were typical fecal contaminants such as members of the genera Bacteroides (2.6%), Macellibacteroides (1.5%), Prevotella (1.4%), and Cloacibacterium (1.2%).

Microbial community composition in the influent, AS and treated effluent samples according to 16S rRNA gene profiling. The composition is displayed at the phylum level. INFL, influent wastewater; AS-LOS, AS at LOS plant; CW-LOS, treated effluent at LOS plant; AS-NLOS2, AS at NLOS2 plant; CW-NLOS2, treated effluent at NLOS2 plant.

Activated sludge of WWTP bioreactors is a complex microbial community consisting of physiologically and phylogenetically heterogeneous groups of microorganisms involved in the removal of major contaminants from wastewater. The composition of AS microbiomes was very different from the microbiome of incoming wastewater (Fig.  1 ). The phyla Campylobacterota (less than 0.5%) and Firmicutes (2–4%) were much less abundant in AS microbiomes. Proteobacteria was the dominant group in the microbiomes of AS (23–40%), but its composition differed from the microbiome of influent wastewater: instead of the fecal microflora (Enterobacterales and others) the AS community harbored lineages involved in the purification processes ( Competibacteraceae , Rhodocyclaceae , Nitrosomonadaceae , etc.). Likewise, Bacteroidota were among the most numerous phyla in AS microbiomes at both LOS (6.5%) and NLOS2 (14.1%), but instead of Bacteroidales mostly comprised Chitinophagales and Sphingobacteriales typical for AS communities. The numerous groups of AS community also included Chloroflexi (22% and 10% in LOS and NLOS2, respectively), Patescibacteria (1.8% and 9.9%), Nanoarchaeota (4.3% and 9.1%), Nitrospirota (3.9% and 7.3%), Verrucomicrobiota and Myxococcota (about 4% in both WWTPs). Bacteria that play an important role in the removal of nitrogen ( Nitrospira and Nitrosomonas ) and phosphorus ( Dechloromonas ), as well as glycogen-accumulating Ca . Competibacter, have been found in large numbers. The abundance of these functional groups is consistent with the high efficiency of nitrogen and phosphorus removal.

The main source of microorganisms in treated effluent is the AS, from which they are washed out; bacteria from the influent water may also be present in minor amounts. Therefore, as expected, the microbiome composition of treated wastewater was similar to that of activated sludge. Consistently, compositions of microbiomes of treated effluent were similar to that of AS samples. However, some differences were observed, in particular, the microbiomes of the treated effluent contained many Cyanobacteria (7.74% and 3.49% for LOS and NLOS2, respectively) which were found in minor amounts both in the influent water and in the ASs (< 0.5%). Probably, these light-dependent bacteria proliferate in the final clarifier and then can be easily washed out with the effluent.

Diversity of resistomes

The results of metagenomic analysis of incoming wastewater revealed 544 ARGs in the assembled contigs, classified into 33 AMR gene families (Table 2 and Supplemental Table S3 ). Among the most numerous were classes A, C, D and metallo- beta-lactamases, rifampin ADP-ribosyltransferase, Erm 23S ribosomal RNA methyltransferase, aminoglycoside nucleotidyl-, acetyl- and phospho-transferases, the ABC-F type ribosomal protection proteins, chloramphenicol acetyltransferase, trimethoprim-resistant dihydrofolate reductase, quaternary ammonium compound efflux SMR transporters, lincosamide nucleotidyltransferases, tetracycline efflux MFS transporters and tetracycline resistance ribosomal protection proteins (Table 2 ). These genes may enable antibiotic inactivation (373 genes), target protection (85 genes), efflux (44 genes) and target replacement (25 genes).

The abovementioned genes confer resistance to most of commonly used drugs: beta-lactams (198 genes), macrolides (74 genes), rifamycin (60 genes), aminoglycosides (51 genes), tetracycline (27 genes), phenicols (27 genes), diaminopyrimidines (19 genes), quaternary ammonium compounds (16 genes), glycopeptides (15 genes), lincosamide (13 genes), fosfomycine (12 genes) and drugs of 11 others classes (Fig.  2 ).

ARGs identified in wastewater and AS samples categorized by drug classes.

About twice less ARGs were identified in AS samples from both WWTPs. Like in the influent, beta-lactamases of classes A, D, and metallo-beta-lactamases were the most numerous, while only a few genes for class C enzymes were found (Table 2 ). Other families of ARGs, numerous in the influent, were also numerous in AS microbiomes. A notable difference between the resistomes of the AS samples is the greater number of rifampin-ADP-ribosyltransferase genes ( arr ) in NLOS2 compared to LOS (63 vs 33). The largest number of arr genes was assigned to Bacteroidota, and the lower relative abundance of this phylum in AS at LOS likely explains these differences. Like in the wastewater, resistance to beta-lactams, macrolides, rifamycin, aminoglycosides, and tetracyclines was the most common (Fig.  2 ). On the contrary, genes for some drug classes were underrepresented in AS resistomes, especially for diaminopyrimidines (3 and 2 genes for LOS and NLOS2, respectively) and glycopeptide antibiotics (2 and 0 genes).

The results of metagenomic analysis of treated effluent showed that the diversity of these resistomes was only slightly higher than that of the corresponding AS samples. This result was expected since the main source of microorganisms in the effluent is activated sludge, from which they are partially washed. However, resistomes of treated effluent at both WWTPs contains about twice more class A beta-lactamase genes than AS samples suggesting less efficient absorption of their host bacteria at AS particles (Table 2 ).

Quantitative analysis of antibiotic resistance genes of WWTP

The results described above provide information on the diversity of resistance genes, but not on their abundance in the metagenomes, which depends on the abundance of corresponding bacterial hosts. To quantify the shares of individual ARGs in the metagenome and resistome, the amounts of metagenomic reads mapped to the corresponding ARGs in contigs were determined. In total, the resistome accounted for about 0.05% of the metagenome of wastewater supplied for treatment, while the shares of resistomes in the metagenomes of AS and treated effluent samples were 0.02% and 0.014% at the LOS and NLOS2 WWTPs, respectively.

Quantitative analysis of the content of individual ARGs in metagenomes showed that the structure of the influent resistome was very different from that of AS and treated effluent. The relative content of ARGs accounting for more than 1% in at least one analyzed resistome is shown in Fig.  3 . The LOS and NLOS2 WWTPs differed significantly from each other, and the differences between the AS and effluent resistomes at each WWTP were much less pronounced.

The relative abundancies of particular ARGs in the resistomes. Only ARGs with shares greater than 1% in at least one sample are shown, all other ARGs are shown as “others”.

The resistome of the influent was not only the most diverse, but also the most even in composition. The shares of none of the ARGs exceeded 5% of the resistome, and the 23 most common ARGs accounted for a half of the resistome. The most abundant ten ARGs were qacE, sul1, ampC, blaOXA, msr(E), erm(B), mph(E), tet(C), aph(3'')-Ib and aph(6)-Id, conferring resistance to antiseptics, sulfonamides, beta-lactams, macrolides, aminoglycosides (streptomycin), and tetracyclines.

AS and treated effluent at LOS plant was strongly dominated by a single AGR type, class C beta-lactamase ampC , accounting for about 45% of their resistomes. This gene was also the most abundant one in the resistomes of AS and effluent at NLOS2 (14.8% and 18.2%, respectively). Apparently it originates from the influent wastewater supplied for treatment where its share in the resistome was 3.2%. AmpC β-lactamases are considered clinically important cephalosporinases encoded on the chromosomes and plasmids of various bacteria (especially Enterobacteriaceae ), where they mediate resistance to cephalothin, cefazolin, cefoxitin and most penicillins 35 . Close homologues of this gene, with a nucleotide sequence identity of 99.8–100%, have been found in plasmids and chromosomes of various Proteobacteria ( Thauera, Sphingobium, Aeromonas etc.). Since in all samples ampC was found in short contigs with very high coverage, it is likely widespread in the genomes of various bacteria in different genetic contexts.

The second most abundant ARG in the resistomes of AS samples was sulfonamide-resistant dihydropteroate synthase ( sul1 ). It accounted for 4–5% of AS and treated effluent resistomes in LOS and for about 11% in NLOS2, while its share in the influent water resistome was about 5%. The sul1 gene is usually found in class 1 integrons being linked to other resistance genes, including qacE 36 . Consistently, sul1 and qacE were found in one contig assembled for the influent water samples and assigned to Gammaproteobacteria. Another sulfonamide-resistance gene, sul2 , was also numerous, accounting for about 2% of the resistomes in the influent and LOS samples, and for about 4% in the AS and water treated at NLOS2.

Since ARGs entering the activated sludge and then into the treated effluent originate mostly from wastewater supplied for treatment, the absolute majority of ARGs present in the influent in significant amounts (more than 0.2% resistome) in were also found in AS and effluent samples. The only exception macrolide 2′-phosphotransferase gene mph(B) accounting for 0.51% in the influent resistome. Likewise, all ARGs accounting for more than 0.2% of resistomes in the treated effluent were present also in the influent.

Potential multidrug resistant strains

One of the most important public health problems is the spread of multidrug resistant pathogens (MDR), which refers to resistance to at least one agent in three or more chemical classes of antibiotic (e.g. a beta-lactam, an aminoglycoside, a macrolide) 37 . Such strains can arrive with wastewater entering the treatment, and also form in AS communities. AS are dense and highly competitive microbial communities, which, along with the presence of sublethal concentrations of antibiotics and other toxicants in wastewater, creates ideal conditions not only for the selection of resistant strains, but also for the formation of multiple resistance through horizontal gene transfer 4 . To identify MDR bacteria, we binned metagenomic contigs into metagenome-assembled genomes (MAGs) and looked for MAGs comprising several ARGs. Only MAGs with more than 70% completeness and less than 15% contamination were selected for analysis: 117, 56, 72, 94 and 121 for influent, AS of LOS, effluent of LOS, AS of NLOS2 and effluent of NLOS2, respectively. Five MAGs of MDR bacteria were identified in the metagenome of the influent, one—in AS of LOS, two—in the LOS effluent and one in the NLOS2 effluent (Table 3 ). These MAGs were assigned to unclassified genus-level lineages of Ruminococcaceae and Cyclobacteriaceae, Phocaeicola vulgatus, Streptococcus parasuis, Ancrocorticia sp., Enterococcus sp., Bacillus cereus and Undibacterium sp.

Disscussion

We characterized the composition of microbial communities and the resistomes of influent wastewater, activated sludge and treated effluent from two WWTPs in city of Moscow, where various biological water treatment technologies are used. Among the predominant bacteria in the influent wastewater we found mainly fecal contaminants of the genera Collinsella , Bacteroides , Prevotella , Arcobacter , Arcobacteraceae , Blautia , Faecalibacterium, Streptococcus , Acinetobacter , Aeromonas and Veillonella 38 , 39 , 40 , 41 , 42 , 43 . Previously, we performed 16S rRNA gene profiling of wastewater before and after treatment at one WWTP (LOS) and revealed that all abovementioned potential pathogens were efficiently removed and their relative abundance in the water microbiome decreased by 50‒100 times 44 . Similar pattern of removal of potential pathogenic bacteria was observed here for NLOS2 where another water treatment technology is used.

An important indicator of the dissemination of ARG is the proportion of the resistome in the entire metagenome before and after wastewater treatment. In the influent, the resistome accounted for about 0.05% of the metagenome, which corresponds to approximately two ARGs per bacterial genome. Approximately the same values are typical for most countries 3 . After treatment, the fraction of the resistome in the wastewater metagenomes decreases, but, surprisingly, only by 2–4 times. However, since the total concentration of microorganisms in treated effluent is approximately two orders of magnitude lower than in raw wastewater, it is likely that the total abundance of ARGs in the treated effluent is significantly reduced.

Apparently, fecal contaminants effectively removed during treatment are not the only carriers of ARG in wastewater, which are also found in bacteria characteristic of activated sludge and thus appearing in the effluents. Unfortunately, due to the high diversity of microbiomes and the tendency of ARG to be present in multiple copies in different genomic environments, most of the contigs containing ARG turned out to be short, which did not allow to define their taxonomic affiliation.

The resistome of influent water includes 26 ARGs, the share of which is more than 1%. Among of them the prevalence of ampC, aadA, qacE, bla, qacF and qacL is specific for Moscow WWTPs, since these genes were not among the 50 most common ARGs according to the results of a worldwide analysis of wastewater resistomes in large cities 3 . Different ARGs were most “evenly” represented in the influent wastewater while in the AS and treated effluent, a clear selection of particular types of ARGs was observed, which obviously reflects a change in the composition of microbiomes. A vivid example is the increase in the proportion of ampC in the resistomes, especially at LOS.

The discovered ARGs can confer resistance to most classes of antibiotics and among the resistomes of the studied WWTPs in the city of Moscow, genes conferring resistance to beta-lactam antibiotics were the most common, they accounted for about 26% of the resistome in the water supplied for treatment (Fig.  4 ). Similar values have been observed for wastewater in some other countries, particularly in Eastern Europe and Brazil, where 20 to 25% of reads were assigned to ARGs conferring resistance to beta-lactams 3 . According to data for 2021, beta lactams accounted for about 40% of the total antibiotic consumption in Russia in the medical sector 45 .

The relative abundancies of ARGs in the resistomes categorized by drug classes.

Like in most wastewater resistomes in different countries, ARGs conferring resistance to macrolides, aminoglycosides and tetracycline were also among the most abundant in wastewater from Moscow (Fig.  4 ). Resistance to macrolides, rather than beta-lactams, was most common in wastewater from most countries in Europe and North America, while in Moscow ARGs to macrolide were the second most common. Macrolides and tetracyclines are also widely used in medicine in Russia (20% and 5% of total antibiotic consumption in 2021, respectively). On the contrary, medical consumption of aminoglycosides in Russia is rather low (< 1% of the total), therefore, the high abundance of relevant ARGs was unexpected. The opposite pattern was observed for quinolones, which make up about 22% of the antibiotics used in medicine, but their ARGs accounted for only about 1% of the resistome. However the main mechanisms of resistance to quinolones, mutations in the target enzymes, DNA gyrase and DNA topoisomerase IV, and increased drug efflux 46 , were not addressed in our study.

A peculiar feature of Moscow wastewater resistome was the high content of resistance genes to sulfonamides (about 9%), which were not among the major genes in wastewater resistomes worldwide 3 . Sulfonamides are synthetic antimicrobial agents that currently have limited use in the human medicine, alone or mainly in combination with trimethoprim (a dihydrofolate reductase inhibitor), in the treatment of uncomplicated respiratory, urinary tract and chlamydia infections 7 , 47 . Different sulfonamide ARGs ( sul1, sul2 and sul3 ) were detected in the wastewater in the some countries, including Denmark, Canada, Spain and China, applying culture dependent, independent and qPCR methods 7 . The opposite picture was observed for streptogramin resistance genes, which were among the ARGs in the majority of resistomes worldwide, but in Moscow wastewater they accounted for less than 1%. This is probably due to the limited use of this drug in Russia.

Another distinguishing feature of the resistome of wastewater in Moscow is the high content of ARGs conferring resistance to quaternary ammonium compounds (QAC), about 9%. It can be explained by the frequent use of these antiseptics in medicine. QACs are active ingredients in more than 200 disinfectants currently recommended for inactivation the SARS-CoV-2 (COVID-19) virus 48 . A recent study showed that the number of QACs used to inactivate the virus in public facilities, hospitals and households increased during the COVID-19 pandemic 49 . Indeed, the results of a study dedicated to the study of wastewater resistome worldwide 3 did not reveal the presence of QAC ARGs in the wastewater, since the samples for this study were collected before the pandemic.

An important issue is the extent to which different water treatment technologies remove ARGs. The effective removal of ARG was primary due to a decrease in the concentration of microorganisms in treated effluent, since the share of resistome in the metagenome after treatment decreased by only 2.6 –3.7 times and the NLOS2 plant appeared to be more effective in this respect. However, compared to LOS, treated effluent at NLOS2 contains approximately twice as much suspended solids, probably due to poorer settling characteristics of the sludge indicated by the higher SVI. Therefore, the overall efficiency of removing ARGs from wastewater at two WWTPs may be similar.

Considering the relative abundances of ARGs in the resistomes, genes conferring resistance to macrolides and tetracyclines were removed more efficiently than beta lactamases, especially ampC , and rifampin ADP-ribosyltransferase genes. The low efficiency of removal of the ampC gene and the increase in its abundance in the resistome after wastewater treatment were previously reported for WWTPs in Germany 50 . Efficient removal of ARGs to macrolides ( ermB, ermF, mph(A), mef(A) ) and tetracyclines ( tet(A), tet(C), tet(Q), tet(W) ) has been reported in a number of studies worldwide 51 . ARGs enabling resistance to sulfonamides, tetracyclines and chloramphenicol were more efficiently removed at LOS than at NLOS2, while the opposite was observed for beta lactamases (Fig.  4 ). The later became the most abundant class of ARGs in the treated effluent.

Metagenomic analysis not only identified resistance genes, but also revealed probable MDR strains based on the analysis of assembled MAGs. We identified 9 such strains in both influent, AS and treated effluent. The real number of MDR strains is probably higher, since only a small fraction of all metagenomic contigs was included in the assembled high quality MAGs.

Phocaeicola vulgatus , (formerly Bacteroides vulgatus ), is a mutualistic anaerobic bacteria commonly found in the human gut microbiome and frequently involved in human infections. The results of whole genome analysis showed presence of blaTEM-1 and blaCMY-2 ARGs, which confers resistant to beta-lactams 52 , 53 . P. vulgatus was also identified as potential host for the transmission of tetracycline ARGs 54 . Streptococcus parasuis is an important zoonotic pathogen that causes primarily meningitis, sepsis, endocarditis, arthritis, and pneumonia in both pigs and humans 55 . A variety of MDR strains of this bacterium have been described. For instance, S. parasuis strain H35 was isolated from a lung sample of a pig in China; several ARGs, including optrA , catQ , erm(B), lsa(E), msr(D), mef(A), mdt(A), tet(M), lnu(B), aadE and two copies of aacA-aphD , were found in the chromosome and cfr(D) was detected on plasmid pH35-cfrD 56 . MDR strain of Bacillus cereus was identified in the effluent water microbiome. This bacterium is known as human pathogen and a common cause of food poisoning with toxin-producing property 57 . Bacillus cereus was isolated from drinking water treatment plant in China and antimicrobial susceptibility testing revealed that it was resistant to cefoxitin, penicillin tetracycline 58 , macrolide-lincosamide-streptogramin (MLSB), aminoglycoside and tetracycline antibiotics 59 . Assembled MAG B.cereus from effluent water contained ARGs conferring to macrolides, beta-lactams, fosfomycin and streptogramin and may be considered as MDR strain. Genomes of members of the genera Streptococcus (AS of LOS) and Enterococcus (influent), not identified at the species level, were found to contain multiple ARGs. Most of species of these genera are opportunistic and true pathogens known for their drug resistance 60 , 61 . One MAG from the influent water metagenome was assigned to uncultured lineage of the family Ruminococcaceae. Members of this family are typical non-pathogenic gut inhabitants, although genomes of some strains could harbor ARGs 62 .

Three MAGs retrieved from influent wastewater microbiome ( Ancrocorticia ) and treated effluent water ( Cyclobacteriaceae and Undibacterium ) were found to contain several ARGs. However, we found no evidences about pathogenic and MDR strains in these taxa. It is possible that these environmental bacteria acquired ARGs via horizontal gene from outside their lineages. WWTPs are an ideal environment for horizontal gene transfer (HGT), since when bacteria are exposed to strong selective pressures, such as the presence of antimicrobials, the horizontal acquisition of ARGs enables genetic diversification and create the potential for rapid gains in fitness 63 .

Conclusions

Metagenome sequencing of the raw wastewater, activated sludge and treated wastewater at two large WWTPs of the Moscow city revealed several hundreds of ARGs that could confer resistance to most commonly used classes of antibiotics.

Resistome accounted for about 0.05% of the wastewater metagenome and after wastewater treatment its share decreased by 3–4 times.

The resistomes were dominated by ARGs encoding resistance to beta-lactams, macrolides, aminoglycosides, tetracycline, QAC, and sulfonamides. A peculiar feature of Moscow wastewater resistome was the high content of ARGs to sulfonamides and limited occurrence of resistance to streptogramins.

ARGs for macrolides and tetracyclines were removed more efficiently than ARGs for beta-lactamases.

A comparison of wastewater resistomes from Moscow and around the world suggested that the abundance and content of ARG in wastewater depend on social, medical, and environmental factors.

Data availability

The raw data generated from 16S rRNA gene sequencing and metagenome sequencing have been deposited in the NCBI Sequence Read Archive (SRA) and are available via the BioProject PRJNA945245.

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Acknowledgements

This work was partly supported by the Russian Science Foundation (Project 22-74-00022 to S.B.).

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S.B. and N.V.R. designed and supervised the research project; A.G.D. collected the samples and analysed chemical composition of wastewater; A.V.M. performed 16S rRNA gene profiling and metagenome sequencing; S.B., A.V.B., N.V.P., and N.V.R. analysed the sequencing data; S.B. and N.V.R. wrote the manuscript. All authors have read and agreed to the published version of the manuscript.

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Begmatov, S., Beletsky, A.V., Dorofeev, A.G. et al. Metagenomic insights into the wastewater resistome before and after purification at large‑scale wastewater treatment plants in the Moscow city. Sci Rep 14 , 6349 (2024). https://doi.org/10.1038/s41598-024-56870-0

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For affordable accommodation of students and make their living experience safe and better, the University maintains a comfortable dormitory. Every room is shared by two or three students, and each floor has a shared kitchen where students can cook their food. Members of the dormitory help the newcomers to settle in their new homes. For the safety of the students, the University’s security team maintains 24-hour surveillance and is capable of providing emergency response, if required.

To help students adjust to life at university, it has a dedicated Student Support System in place. Every group of new students is assigned to two professors who guide the students not only about studying but about living as well, helping students adjust to the new environment and feel comfortable.

To keep students fit and active, Sports Center on the campus is equipped with facilities to play various sports, including badminton, basketball, volleyball, table tennis, swimming, football, hockey, chess, etc. Student can unleash their creativity by indulging in extracurricular adventures offered by Student Organizations and Societies. On the campus, there are ample opportunities for self-improvement and taking part in music, dance, sports competitions, and theater. 

For peer support, the University has a Student Council in place which offers support in academic as well as non-academic matters making student life stress free.

For the social upliftment and help students connect with the society and local people, they are involved in community and welfare organized by the University, including medical outreach, health awareness programs, and blood donation camps.  The University Volunteer Center organizes a number of volunteer activities to help students contribute to social causes.

Living in Moscow, students can explore its cultural heritage, museums, historic buildings, the world-famous Alexander Garden, and much more. For traveling in Moscow, students don’t face any problems, thanks to its convenient and cheap transportation system, especially the Moscow Metro.

With the charm of Moscow and all the student facilities and support services offered by the University, student life at Pirogov Medical University is a delight.

TOP MEDICAL UNIVERSITIES IN RUSSIA

Perm State Medical University

Tver State Medical University

Orenburg State Medical University

Mari State University

Siberian State Medical University

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China's bid to decarbonize may have hidden costs

by Laura Reiley, Cornell University

Environmentalists rejoiced when China announced its commitment to reach carbon neutrality by 2060, but the decarbonization of China—which emits 27% of global carbon dioxide and a third of the world's greenhouse gases—may come with hidden costs and hard environmental choices, according to new research.

In a paper published in Communications Earth & Environment , Stefano Galelli, associate professor in the School of Civil and Environmental Engineering, in Cornell Engineering, and colleagues attempt to quantify how decarbonizing the China Southern Power Grid, which provides electricity to more than 300 million people, will negatively impact river basins, most of which run from China into downstream countries, and will reduce the amount of cropland in China.

"If we think of any major technological change, they always have costs and unintended consequences," Galelli said. "The sooner we realize and address them, the more sustainable and equitable the energy transition will be. We have to do it right."

Decarbonizing the grid by 2060 may be technically feasible but would require building several dams for hydropower production (roughly 32 GW) and converting about 40,000 square kilometers of cropland to support growth in solar and wind, Galelli said. Most of the dams would be placed on transboundary rivers, meaning those shared by two or more countries, resulting in potential negative ecological impacts in both China and downstream countries.

"A fundamental problem is these dams will alter the river flow," Galelli said. "Changing the way water flows in the river has huge impacts on the riverine ecosystems and the communities that rely on them."

Two major transboundary river basins that will be impacted are the Salween and Mekong, both major biodiversity hotspots, Galelli said. The Salween is shared by China (upstream) and Myanmar; the Mekong by China (upstream), Myanmar, Thailand, Laos, Cambodia, and Vietnam—thus, the impacts of additional damming are shared.

As an example, he said, Cambodia's Lower Mekong Basin is the center of that country's inland fishing industry. Cambodia has one of the world's largest inland fisheries, a main source of protein for the population of 16.8 million. With more than 100 large hydropower dams already on the Mekong River and its tributaries, and several more planned or under construction, the implications associated with China building additional dams must be considered, Galelli said.

Dams block the transport of sediments and nutrients from the upper reaches to the river mouth, and this reduces the productivity of ecosystems and fisheries. Blocking the transport of sediments also affects river deltas: If sediments do not reach the delta, saline intrusion becomes a bigger problem. Dams can also impact migratory fish species.

"The costs may outstrip the benefits," he said. "It would be important to account for these impacts when planning large-scale decarbonization efforts."

Decarbonization would also lead to ecological and sociological trade-offs in terms of land use, he said.

China's President Xi Jinping has ramped up efforts and rhetoric around food security, emphasizing self-sufficient food production in lieu of relying so heavily on imports. But with 18% of the world's population and only 10% of the planet's arable land, that's a tall order—one made even tougher with more land given over to support solar and wind power.

"Excluding sites that are protected—cities and national parks, for instance—what you're left with is cropland on which to build solar and wind power," Galelli said.

And with China's electric vehicle industry seeing stratospheric growth—China now leads global electric vehicle sales—demand for electricity will continue to rise. Coal power plants have historically been the dominant source of electricity for the China Southern Power Grid—but building enough wind and solar arrays to replace the electricity supply guaranteed by conventional coal plants will take up a lot of space, Galelli said.

And that space required for the construction of solar and wind plants may not be equitably divvied up. Their research shows that 43% of the total land requirements would likely be focused on the Guangxi province, where crops and grassland constitute the vast majority of the land. This might be a heavy burden for the province and result in significant ecological, social, and financial costs to local communities.

Many new solar technologies are being developed, he said. Floating solar panels could cover some of the surface of lakes behind existing and planned dams (fully covering the surface of these lakes would impede their oxygenation). Solar on roofs is also viable, but in general represents a small amount of surface area and can be plagued by mechanical problems.

Galelli lists agrivoltaics, which combines solar with agricultural activities; carbon sequestration from gas and coal plants; more efficient batteries; and electricity demand management as other promising technologies.

"Our work is based on a projection of need in 2060, but need is not set or known, and 36 years is a lot of time for technical innovation," he said.

As we make strides toward decarbonizing, he said, China is at the forefront.

"Doing it in strategic ways is very important. We have to start with ones that are less impactful," Galelli said. "We can make decisions that balance decarbonization efforts with the protection of local communities, water and land resources."

Journal information: Communications Earth & Environment

Provided by Cornell University

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Daily ingestion of alkaline electrolyzed water containing hydrogen influences human health, including gastrointestinal symptoms

Yoshinori tanaka.

1 Appliances Company, Panasonic Corporation, Shiga, Japan

Yasuhiro Saihara

Kyoko izumotani.

2 Osaka Municipal Health Promotion Center, Osaka, Japan

Hajime Nakamura

3 Osaka City University, Graduate School of Medicine, Osaka, Japan

Author contributions

In Japan, alkaline electrolyzed water (AEW) apparatus have been approved as a medical device. And for the patients with gastrointestinal symptoms, drinking AEW has been found to be effective in relieving gastrointestinal symptoms. But some users of AEW apparatus do not have abdominal indefinite complaint. Little attention has been given to the benefit for the users which have no abdominal indefinite complaint. The object of this study is to evaluate the effect on health, including gastrointestinal symptoms, when a person without abdominal indefinite complaint, etc ., drinks AEW on a daily basis. A double-blind, randomized controlled trial has been designed. Four-week period of everyday water drinking, PW drinking group: drink purified tap water as a placebo, AEW drinking group: drink alkaline electrolyzed water which made by electrolysis of purified tap water. Before the experiment and after the 4-week period of water drinking, Blood tests, physical fitness evaluations, and questionnaire evaluations is conducted. In this study, we did not specifically select patients with gastrointestinal symptoms. Sufficiently clear effect could not be confirmed. But the stools were more normal, and, as shown in the previous report, that drinking AEW is considered to contribute to intestinal normalization. In addition, when drinking AEW, a high proportion of the respondents said that they felt they were able to sleep soundly, and the proportion of subjects who answered that they felt good when awakening increased. The effect of reducing oxidative stress, thus allowing for improved sleep, was exhibited by drinking AEW containing hydrogen, which is considered to be an antioxidant substance. This research were approved by the Ethics Committee of the Osaka City University Graduate School of Medicine (No. 837) and were registered in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN ID: UMIN000031800) on March 22, 2018.

I NTRODUCTION

In Japan, water which is obtained on the cathode side by the electrolysis of tap water is called alkaline electrolyzed water (AEW) or reduced hydrogen water. 1 Improvement of gastrointestinal symptoms by ingesting AEW has been confirmed by Japanese researchers. For example, Naito et al. 2 reported the inhibitory effect of AEW ingestion on gastric mucosal disorder caused by aspirin, and Hayakawa et al. 3 reported the inhibitory effect of AEW ingestion on abnormal intestinal fermentation. Tashiro et al. 4 examined the effect of ingesting AEW or purified tap water (PW; as a placebo) at a rate of at 500 mL per day for 4 weeks in patients who had abdominal pain such as heartburn, stomach discomfort, abdominal bloating, diarrhea, constipation, etc ., and reported that the results of the AEW group were superior to those of the placebo group. 5 , 6 From these results, apparatus that produce AEW have been approved as medical devices by the Japanese Ministry of Health, Labour and Welfare. AEW is thought to be effective for functional gastrointestinal disorders. 5

Since AEW is produced by electrolyzing water, hydroxide ions, which are alkaline in nature, are generated. Hydrogen molecules are also generated on the electrode surface and dissolved in water. Therefore, AEW is alkaline water containing hydrogen. 1 In conventional efficacy studies, evaluations with respect to ingesting AEW have typically been conducted focusing on the alkalinity of the water. 2 , 3 , 4 , 5 In recent years, however, the assumed effectiveness of the antioxidant effect of dissolved hydrogen on various diseases has been reported. 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 Nevertheless, some users of AEW apparatus do not have any definite abdominal symptoms. In many cases, they are drinking AEW on a daily basis to improve their health, and many users also feel health benefits such as improvement in exercise capacity 12 . These may be thought to be due to the action of dissolved hydrogen. There have been no researched studies of these in detail. The object of this study is to evaluate the effect of daily ingestion of AEW on health, including gastrointestinal symptoms, in subjects without any definite abdominal symptoms.

P ARTICIPANTS AND M ETHODS

Participants.

Healthy men and women (20–60 years) who use the Osaka City Citizen Health Development Consultation Center were selected as test subjects to determine the health effect of daily AEW ingestion. It was aimed to clarify whether general subjects without gastrointestinal symptoms have another good effect besides gastrointestinal symptoms by drinking AEW which is good for gastrointestinal symptoms. We explained this purpose to the subjects and asked for research participation. Written informed consent was obtained from all subjects. All procedures used in this research were approved by the Ethics Committee of the Osaka City University Graduate School of Medicine (No. 837) and were registered in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN ID: UMIN000031800) on March 22, 2018. This study follows the Consolidated Standards of Reporting Trials (CONSORT) guidelines. A double-blind, randomized controlled trial has been designed, and the research design is shown in Figure 1 .

Research design.

Note: PW: Purified tap water; AEW: alkaline electrolyzed water.

Subjects were randomly divided into two groups, with an AEW group ( n = 30) and a PW group ( n = 30). Blood tests, physical fitness evaluations, and questionnaire evaluations were conducted before the experiment was initiated. Subjects were provided with AEW apparatus 1 that had been modified to produce only AEW or PW. They ingested 500 mL or more of freshly produced AEW or PW per day (they were required to ingest 200 mL immediately after awakening, and 300 mL or more during the rest of the day). After the end of the four-week period, blood tests, physical fitness evaluations, and questionnaire evaluations were conducted again to check whether the ingestion of AEW for four weeks had beneficial effects on the health of the subjects.

Blood sample/urinalysis

General blood test: Red blood cell count, white blood cell count, hemoglobin, hematocrit, and platelet count.

Blood biochemical examination: Total protein, albumin, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), γ-GTP, total cholesterol, high-density lipoprotein (HDL), cholesterol, low-density lipoprotein (LDL) cholesterol, neutral fat, uric acid, creatinine, and blood sugar.

Urinalysis: Urine sugar, urine protein, urine occult blood, and urine pH.

Physical measurements

Right/left grip strength, right/left leg muscle strength, vertical jump, whole body reaction time, standing time on one leg with eyes closed, sit-up, seated forward bend, and resting blood pressure.

Questionnaire variables

Gastrointestinal symptoms (stomachache, heartburn, heavy stomach, lower abdominal pain, bloated stomach), urinary frequency, condition of the stools (fecal properties and bowel movement), and physical condition (sleep quality and upon awakening).

Statistical analysis

In the blood data, the urinalysis and physical measurement values, the statistical significance of the average difference (before and after AEW, PW drinking) was analysed using a paired t -test (Statcel 4 Software [OMS Publishing, Saitama, Japan). The questionnaire data (before and after AEW, PW drinking) was analysed by the Wilcoxon signed-rank test using the same Statcel 4 software. Differences for which P values of < 0.05 and < 0.01 were inferred as significant.

Conditions of subjects and water quality

Subjects with abdominal symptoms such as heartburn, stomach discomfort, abdominal bloating, diarrhea, and constipation were used in the study previously performed. 4 , 5 For the current study, subjects aged 20 to 69 years were randomly selected among medical checkup examinees who visited the Osaka City Citizen Health Development Consultation Center, and then divided into two groups. One group ingested PW while the other ingested AEW. Neither the subjects nor the experimenters knew which group the subjects belonged to. Figure 2 shows that no significant differences were found in dispersion of mean values and distribution values.

Age distribution of subjects.

Each subject was provided with an AEW apparatus that had been modified to either produce or not produce AEW, and asked to install it at their home. In order to verify the quality of the drinking water, the water produced by the apparatus was taken into aluminum containers and collected when the subjects came in for measurement. Figure 3 shows the water quality distribution of each drinking water.

Water quality distribution of two types of drinking water.

Because we selected subjects who live in or around Osaka City, the tap water from either the same or a nearby water source was used for the evaluation. For this reason, the tests have been conducted using water of equivalent quality and which shows little bias in the distribution of ions.

Regarding the water before and after the electrolysis, the pH was 7.6 ± 0.2 for the PW group, and 9.2 ± 0.2 for the AEW group. Dissolved hydrogen concentration was not measurable at the subjects’ houses because hydrogen easily escapes water. However, for non-electrolyzed and electrolyzed tap water from the same water source and using the same water apparatus, the hydrogen concentration was confirmed as 0 mg/L in the PW group and 0.2 mg/L for the AEW group for the characteristics of the device.

Comparison of hematological values

The hematological data of subjects in the PW group and the AEW group were compared before and after the four-week period, but no significant differences were observed in both groups. This is consistent with the contents of the previous report. 5 However, the HDL cholesterol level, a newly measured value this time, of the AEW group showed a tendency to increase with P = 0.097, as shown in Figure 4 .

Change in HDL cholesterol before and after drinking.

Note: (A) alkaline electrolyzed water (AEW) drinking group, (B) purified tap water (PW) drinking group. HDL: High-density lipoprotein.

Comparison of data related to physical abilities

For the seated forward bend, vertical jump, right/left grip strength, and sit-up, there was no significant difference before and after the 4-week period for both the PW group and the AEW group.

Regarding the whole body reaction time, no significant differences were observed before and after the 4-week period in the case of the PW group, as seen in Figure 5B . However, a significant difference (decrease) ( P < 0.05) was observed in the AEW group, as seen in Figure 5A . As for standing time on one leg with eyes closed, longer times were observed in the AEW group ( P = 0.09), as seen in Figure 6A .

Change in whole body reaction time before and after drinking.

Note: (A) Alkaline electrolyzed water (AEW) drinking group; (B) purified tap water (PW) drinking group.

Changes in the standing time on one leg with eyes closed before and after drinking.

Note: (A) alkaline electrolyzed water (AEW) drinking group, (B) purified tap water (PW) drinking group.

Questionnaire to subjects

As for the questionnaire items, we asked the subjects to provide answers in 3 to 5 points about gastrointestinal symptoms ( Table 1 ), defecation and urination ( Table 2 ), and physical condition ( Table 3 ).

Gastrointestinal symptoms

Note: Scoring 1 to 4, where: Not at all = 1, and Very much = 4.

Defecation and urination

Physical conditionn

Note: Scoring 1 to 3, where: Good = 1, and Bad = 3.

First, as seen in Figures ​ 7 7 to ​ to 11 , 11 , as for gastrointestinal symptoms, sufficiently clear effect could not be confirmed in this study. Next, as seen in Figure 12 , the urinary frequency significantly increased in both groups, likely due to an increase in urine volume resulting from water ingestion. Regarding bowel movement, the stools slightly changed from slightly soft to normal or slightly hard, or from soft to normal ( P < 0.05) in the AEW group, as can be seen in Figure 13A . There was no difference between subjects of the two groups who had answered that they were in “good” or “bad” physical condition.

Change in stomach ache before and after drinking.

Note: Left side: alkaline electrolyzed water (AEW), and right side: purified tap water (PW).

Change in bloated stomach before and after drinking.

Change in urinary frequency before and after drinking.

Note: (A) Alkaline electrolyzed water (AEW) drinking group, and (B) purified tap water (PW) drinking group.

Changes in the condition of stools before and after drinking.

Change in heartburn before and after drinking.

Change in heavy stomach before and after drinking.

Change in lower abdominal pain before and after drinking.

Regarding sleep quality, there was a significant increase ( P < 0.01) in the number of AEW group subjects who responded that they were able to sleep well, as shown in Figure 14A , and there was a significant increase ( P < 0.05) in the number of subjects from the same group who said that they felt good upon awakening, as seen in Figure 15A .

Change in sleep quality before and after drinking.

Changes in the state of getting up before and after drinking.

D ISCUSSION

In Japan, AEW apparatus have been approved as medical devices, and ingesting AEW has been found to be effective in relieving gastrointestinal symptoms. A clinical evaluation of this effect was conducted with patients with gastrointestinal symptoms (heartburn, stomach discomfort, and abdominal symptoms such as abdominal bloating, diarrhea, and constipation). 5

Antioxidant action by hydrogen and gastric acid neutralization by alkaline pH have been considered. 6 In addition, recent studies have shown that the intestinal bacterial flora distribution changes. It seems that these are involved in the normalization of the gastrointestinal activity. 11 However, for this study, patients with gastrointestinal symptoms were not specifically selected. As for these as well as the previous results, in general, there was no difference in the hematological values between the PW group and the AEW group. 5 However, the newly measured HDL cholesterol value showed a tendency to increase with P = 0.097. The increase in HDL cholesterol by ingesting water containing hydrogen is reported by Gadek and colleagues. 16 The effect of hydrogen can be considered to have had an effect in the AEW group this time as well.

As for gastrointestinal symptoms—which showed a significant difference during the previous study (significant improvement of abdominal symptoms and improvement of abnormal bowel movement) 4 , 5 —sufficiently clear effect could not be confirmed by this study because the subjects did not show gastrointestinal symptoms, and very few of them responded that they had abnormal abdominal symptoms and bowel movement before participating in this study. Therefore, we believe this is the reason the answers of the subjects were the same before and after their participation in the study.

However, with respect to bowel movement, the stools slightly changed from soft to normal or slightly hard, or from loose to normal in the AEW group. This reflects that the stools are more normal, and, as shown in the previous report, that ingesting AEW is considered to contribute to intestinal normalization. 4 , 5 , 6 Regarding items other than the gastrointestinal tract, a high proportion of the respondents said that they felt they were able to sleep well, and the proportion of subjects who answered that they felt good when awakening increased. Various studies on the relationship between the ingestion of antioxidant substances and the condition of sleep have been undertaken, 17 and the effect of reducing oxidative stress, thus allowing for improved sleep quality, is exhibited by ingesting AEW containing hydrogen, which is considered an antioxidant substance.

Regarding sports performance, various reports on the effects of sleep on sports performance have concluded that willingly sleeping longer can lead to faster running, shortened reaction time, and improved motivation during practice and games. 18 Improved sleep quality by ingesting AEW is, therefore, believed to help reduce fatigue, ensure appropriate endurance recovery, and improve overall sports performance.

The findings of this study indicate that ingesting AEW on a daily basis improves health and exercise capacity, even in healthy people who do not have gastrointestinal symptoms.

Funding: The study was supported by a grant from Matsushita Electric Works Co., Ltd. Home Appliances R&D Center (to HN).

Conflicts of interest

The corresponding author (YT) is a salaried employee of the Panasonic Corporation. One of the authors (SY) was a salaried employee of the Panasonic Corporation. This study does not alter our adherence to Medical Gas Research policies on sharing data and materials. Another authors (KI and HN) report no conflict of interest related to this manuscript.

Financial support

The study was supported by a grant from Matsushita Electric Works Co., Ltd. Home Appliances R&D Center (to HW).

Institutional review board statement

All procedures used in this research were approved by the Ethics Committee of the Osaka City University Graduate School of Medicine (No. 837) and were registered in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN ID: UMIN000031800) on March 22, 2018.

Declaration of participant consent

The authors certify that they have obtained participant consent forms. In the form, participant have given their consent for their images andother clinical information to be reported in the journal. The patients understand that their names and initials not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Reporting statement

This study follows the Consolidated Standards of Reporting Trials (CONSORT) guidelines.

Biostatistics statement

The statistical methods of this study were reviewed by the biostatistician of the Osaka City University, Osaka, Japan.

Copyright license agreement

The Copyright License Agreement has been signed by all authors before publication.

Data sharing statement

Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures, and appendices). Study protocol and informed consent form will be available immediately following publication, without end date. Results will be disseminated through presentations at scientific meetings and/or by publication in a peer-reviewed journal. Anonymized trial data will be available indefinitely at www.figshare.com .

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Blood test can detect laughing gas and help the police fight whippit abuse

by University of Copenhagen

Forensic blood analysis can reveal whether drivers are high on laughing gas. Researchers hope the method can help the police.

Once again, recreational use of laughing gas has attracted media attention in Denmark. This time, however, focus is on drivers who have inhaled laughing gas before getting behind the wheel—with potentially lethal consequences.

So says Ph.D. Student of Forensic Chemistry Angelica Ørregaard Lindholm at the University of Copenhagen, who is responsible for the new study published in Forensic Science International on driving under the influence of laughing gas.

"Laughing gas can cause disorientation, hallucinations, dizziness, and fainting. So, laughing gas and driving is a dangerous combination," Ørregaard Lindholm explains and adds that it is a common misconception that the drug does not show up on tests.

In the new study, Ørregaard Lindholm and her colleagues show that laughing gas can be detected in a simple blood test .

"We have analyzed 62 blood tests, 52 of which were positive for laughing gas. The police have provided the tests, which are made when they have reason to suspect someone of being under the influence of laughing gas," Ørregaard Lindholm says.

After publishing the study, the researchers have continued analyzing tests. Of the 103 tests they have analyzed since 2020, 90 have been positive.

Since 1 July 2023, it has been illegal, with a few exceptions, to carry laughing gas in public spaces , and this includes cars in public spaces. Being high on laughing gas is not illegal, though.

Laughing gas is also known as nitrous oxide and can be bought in small or large cartridges intended for whipped cream siphons.

"Inhalation of laughing gas can induce short-term euphoria and a sense of weightlessness," Ørregaard Lindholm says.

It is used as a painkiller by dentists and during labor, and here it is safe to use. However, long-term abuse can cause permanent neurological damage.

"Nitrous oxide inactivates the vitamin B12 stores in the body, and they take time to rebuild. If you continue to use laughing gas, your body will begin to suffer from vitamin B12 deficiency, and this will damage the protective myelin sheath that surrounds the nerve fibers," Ørregaard Lindholm explains.

Method must be refined

Even though laughing gas can be detected in the blood, the researchers face several challenges before they are satisfied with the method.

"Our main problem is that the effect is brief and that the gas disappears quickly after inhalation," Ørregaard Lindholm says.

Therefore, the police must act quickly. Otherwise, the gas will not show up on the test.

"This is likely to limit the police's options. For instance, if they are in the countryside and the nearest hospital is far away, they might think that testing is futile and decide not to do the test," Ørregaard Lindholm explains.

Research from the 1970s shows that the half-life of laughing gas is five minutes. Sometimes, though, the researchers found nitrous oxide in the blood three hours after the sample was taken.

Now they want more systematic knowledge of how long laughing gas can be detected in the blood and to which extent it affects the user's ability to drive.

Therefore, the next step for Ørregaard Lindholm and her colleagues is to do a clinical trial with a group of test subjects who will be given laughing gas and asked to operate a car simulator while the researchers do a series of blood tests. The trial will be conducted together with the Center of Head and Orthopaedics at Rigshospitalet and the Division of Transport Science at the Technical University of Denmark.

"Ultimately, we hope our method and the results of the clinical trial will be able to help the police get the proof they need in cases of laughing gas abuse and driving."

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ISSN: 2045-9912

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34 Best Medical schools in Moscow, Russia

Updated: February 29, 2024

• Art & Design
• Computer Science
• Engineering
• Environmental Science
• Liberal Arts & Social Sciences
• Mathematics

Below is a list of best universities in Moscow ranked based on their research performance in Medicine. A graph of 922K citations received by 111K academic papers made by 34 universities in Moscow was used to calculate publications' ratings, which then were adjusted for release dates and added to final scores.

We don't distinguish between undergraduate and graduate programs nor do we adjust for current majors offered. You can find information about granted degrees on a university page but always double-check with the university website.

1. Moscow State University

For Medicine

2. Moscow Medical Academy

3. Russian National Research Medical University

4. RUDN University

5. National Research University Higher School of Economics

6. Moscow Institute of Physics and Technology

7. National Research Nuclear University MEPI

8. Bauman Moscow State Technical University

9. N.R.U. Moscow Power Engineering Institute

10. Russian Presidential Academy of National Economy and Public Administration

11. Moscow State Pedagogical University

12. National University of Science and Technology "MISIS"

13. Mendeleev University of Chemical Technology of Russia

14. Finance Academy under the Government of the Russian Federation

15. Plekhanov Russian University of Economics

16. Moscow Aviation Institute

17. Moscow State Institute of International Relations

18. Russian State Social University

19. Russian State Agricultural University

20. National Research University of Electronic Technology

21. Russian State University of Oil and Gas

22. new economic school.

23. Russian State University for the Humanities

24. Moscow State Technological University "Stankin"

25. State University of Management

26. Moscow State University of Railway Engineering

27. Moscow Polytech

28. Moscow Technical University - MIREA

29. Moscow State Linguistic University

30. Moscow State Mining University

31. Moscow International University

32. Pushkin State Russian Language Institute

33. Russian State Geological Prospecting University

34. moscow state technical university of civil aviation.

Universities for Medicine near Moscow

Medicine subfields in moscow.