Antibiotic resistance determinants among carbapenemase producing bacteria isolated from wastewaters of Kathmandu, Nepal.

The emergence of carbapenem resistant bacteria (CRB) possesses a remarkable threat to the health of humans. CRB and carbapenem resistance genes (CRGs) have frequently been reported in clinical isolates from hospitals, however, their occurrence and distribution in wastewaters from various sources and river water have not been emphasized in Nepal. So, this study aimed to detect carbapenem resistant bacterial isolates and their resistance determinants in river water and different types of wastewaters. River water and both untreated and treated wastewater samples from hospitals, pharmaceutical industries, and municipal sewage were collected in summer and winter seasons. From 68 grab wastewater samples, CRB were detected only in 16 samples, which included eight hospital wastewater, and four each from untreated municipal sewage and river water. A total of 25 CRB isolates were detected with dominance of E. coli (44.0%) and K. pneumoniae (24.0%). The majority of the isolates harbored blaNDM-1 (76.0%), followed by blaOXA (36.0%) and blaKPC (20.0%) genes. Hospital wastewater majorly contributed to the presence of blaNDM-1, blaKPC, and blaOXA along with intI1 genes compared to river water and untreated municipal sewage, especially during the winter season. However, CRB were not detected in treated effluents of hospitals and municipal sewage, and both influents and effluents from pharmaceutical industries. The combined presence of each blaNDM-1 & blaOXA and blaKPC & blaOXA occurred in 16.0% of the bacterial isolates. The increased minimum inhibitory concentration (MIC) of meropenem was significantly associated with the presence of CRGs. The results of this study highlight the significance of carbapenem resistance in bacteria isolated from wastewater and river water, and underscore the necessity for efficient monitoring and control strategies to prevent the dispersion of carbapenem resistance in the environment and its potential consequences on human health.

Microplastic pollution in lakeshore sediments: the first report on abundance and composition of Phewa Lake, Nepal.

Microplastic pollution in a freshwater environment has captured the attention of the scientific world in recent years. Microplastic is a new area of research in the freshwater of Nepal. Hence, the present study aims to examine the concentration, distribution, and characteristics of microplastic pollution in the sediments of Phewa Lake. Twenty sediment samples were collected from 10 sites to cover the vast area (5.762 km2) of the lake. The mean abundance of microplastic was 100.5 ± 58.6 items/kg dry weight. The average abundance of microplastics in five sections of the lake showed a significant difference (test statistics = 10.379, p < 0.05). Fibers (78.11%) dominated the sediments of Phewa Lake in all sampling sites. Transparent was the prominent color observed followed by red and altogether 70.65% of the microplastics detected were found at 0.2-1 mm size class. Fourier transform infrared spectroscopy (FTIR) analysis of visible microplastic particles (1-5 mm) confirmed polypropylene (PP) (42.86%) as the dominant polymer type followed by polyethylene (PE). This study can help to bridge the knowledge gap regarding the microplastic pollution in freshwater shoreline sediments of Nepal. Furthermore, these findings would create a new research area to explore the impact of plastic pollution which has been ignored in Phewa Lake.

Arsenic Contamination in Groundwater: Geochemical Basis of Treatment Technologies.

Arsenic (As) is abundant in the environment and can be found in both organic (e.g., methylated) and inorganic (e.g., arsenate and arsenite) forms. The source of As in the environment is attributed to both natural reactions and anthropogenic activities. As can also be released naturally to groundwater through As-bearing minerals including arsenopyrites, realgar, and orpiment. Similarly, agricultural and industrial activities have elevated As levels in groundwater. High levels of As in groundwater pose serious health risks and have been regulated in many developed and developing countries. In particular, the presence of inorganic forms of As in drinking water sources gained widespread attention due to their cellular and enzyme disruption activities. The research community has primarily focused on reviewing the natural occurrence and mobilization of As. Yet, As originating from anthropogenic activities, its mobility, and potential treatment techniques have not been covered. This review summarizes the origin, geochemistry, occurrence, mobilization, microbial interaction of natural and anthropogenic-As, and common remediation technologies for As removal from groundwater. In addition, As remediation methods are critically evaluated in terms of practical applicability at drinking water treatment plants, knowledge gaps, and future research needs. Finally, perspectives on As removal technologies and associated implementation limitations in developing countries and small communities are discussed.

Impact of air pollution on human health in different geographical locations of Nepal.

According to a recent survey, Nepal's urban air quality has been classified as one of the worst in the globe. A large portion of the country's population is subjected to health risks caused by air pollution. As Nepal has a wide variation in altitude coupled with socio-cultural and biological diversities, it is important to understand the different health hazards in the different geographical regions - Terai, Hills and Mountains. Constantly increasing physical infrastructures (such as transport vehicles, open burning of plastics and other fuels) are the main reasons for the escalating air pollution in the country. This study aims to critically review the current air pollution status in different geographical locations along with its impacts on public health in the country. It has been revealed that irrespective of geographic location, the air pollutants interfere with different human physiological systems related to respiration as well as cardiovascular, ophthalmic, and gastrointestinal functioning. Further, the research findings highlighting the influence of prolonged exposure of the population to the air pollution leading to the significant number of deaths have been presented. A notable rise in the number of hospitalized patients suffering from illnesses related to above mentioned pollution borne cases has been reported.

Occurrence and Distribution of Microplastics from Nepal's Second Largest Lake.

Due to its harmful impact on biota, microplastic pollution is the top priority research in many countries. However, there is hardly any research on microplastic pollution in Nepal's freshwater. Therefore, the present research was accomplished in Phewa Lake to evaluate the occurrence and distribution of microplastic contamination in shoreline sediments. The average abundance of microplastic varied from 55 to 122.5 items/kg dry weight (dw). The highest value appeared on densely populated eastern side of the lake and the western region reported the lowest concentration of microplastic. With regard to the shape, fibers dominated the sediments of Phewa Lake accounting for 62.03%. The dominant color was transparent (23.53%) followed by blue (21.39%). The size category 0.2-1 mm recorded the highest abundance of microplastic. Similarly, Fourier transform infrared spectroscopy (FTIR) reveal the dominant polymer type as polypropylene (PP) and polyethylene (PE). The outcome of this result adds a step toward filling the existing knowledge gap and providing a database on microplastic pollution in Nepal's freshwater.

Prevalence of metallo-ß-lactamases as a correlate of multidrug resistance among clinical Pseudomonas aeruginosa isolates in Nepal.

Pseudomonas aeruginosa is an opportunistic human pathogen that has developed antibiotic resistance (AR) and causes a range of illnesses, including respiratory pneumonia, gastrointestinal infections, keratitis, otitis media and bacteremia in patients with compromised immune system. The production of metallo-ß-lactamases (MBLs) is one of the major mechanisms of AR in this bacterium with ensuing infections difficult to treat. The main goal of this study was to provide a quantitative estimate of MBLs producing clinical P. aeruginosa isolates among the Nepalese patients and determine if MBL correlates with multi-drug resistance (MDR). Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guideline was followed for meta-analysis of relevant literature using PubMed, Research4Life, and Google Scholar. The prevalence of MBLs in P. aeruginosa from clinical samples was determined using R 4.1.2 for data pooled from studies published until 2021. The meta-analysis of a total of 19 studies selected (of 6038 studies for which titles and abstracts were reviewed) revealed the prevalence of MBLs producing P. aeruginosa (MBL-PA) was 14 % (95 % CI: 0.10-0.19) while MDR isolates among P. aeruginosa was 42 % (95 % CI: 0.30-0.55) in Nepal. Combined Disc Test was predominantly used phenotypic method for confirming MBLs phenotypes among the studies. Sputum was the most common specimen from which MBL-PA was recovered. A significant positive correlation was observed between MDR and MBL production in P. aeruginosa. We conclude that MBL producing strains are widespread among the clinical isolates of P. aeruginosa in Nepal and responsible for emerging MDR strains. It is paramount that antibiotics prescription against the bacterium should be monitored closely and alternative therapeutic modalities against MBL-PA explored.

Simultaneous removal of aromatic pollutants and nitrate at high concentrations by hypersaline denitrification:Long-term continuous experiments investigation.

If we can use toxic aromatic compounds as supplementary carbon source, the simultaneous removal of nitrate (NO3-) and aromatic compounds may be achieved at much lower chemical costs. This study uses the expanded granular sludge bed (EGSB) reactors to investigate the hypersaline (> 3%) denitrification performance, the removal of aromatic compounds, i.e., aniline, phenol, and their mixture, and the mechanisms involved in. The four reactors exhibit high removal efficiency of NO3- (> 92.8%) and aromatic compounds (> 73.9%) at 0-1200 mg/L of aromatic compounds. The formation of toxic intermediates such as catechol and azo dyes is revealed by gas chromatography mass spectrometry (GC-MS) with and without N,O-Bis(trimethylsilyl) trifluoroacetamide (BSTFA) derivation, and their toxic effects lead to the lower cell survival ratios after exposing to phenol (64.2% ∼ 68.9%) than to aniline and mixture (72.7% ∼ 78.0%). The stable performance is associated with the more secretion of extracellular polymeric substances (EPS) and the adsorption of pollutants on EPS, and this was indicated from the higher fluorescence intensity in three-dimensional excitation-emission matrix (3D-EEM). Moreover, the Halomonas and Azoarcus show high abundance and play important roles in the removal of both NO3- and aromatic compounds. Besides, quantitative real time PCR (RT-qPCR) results demonstrate the key role of highly abundant nosZ and nirS genes in denitrification. The toxic organics in industrial wastewaters are potentially feasible carbon sources for denitrification even under high-salinity stress.

Microplastic pollution in urban Lake Phewa, Nepal: the first report on abundance and composition in surface water of lake in different seasons.

Microplastics are man-made pollutants which have been detected in surface water and groundwater. Research on microplastic concentration in aquatic environment is attracting scientists from developing countries, but in Nepal no information regarding microplastic in freshwater system is available. Therefore, this study investigates the presence and abundance of microplastic in lake surface water of Phewa Lake, the second largest lake in Nepal. The average concentration of microplastic for surface water was 2.96 ± 1.83 particles/L in winter (dry) season and 1.51 ± 0.62 particles/L in rainy (wet) season. Significant difference with t = 4.687 (p < 0.01) in microplastic concentration was observed in two different seasons. Fibers (93.04% for winter and 96.69% for rainy season) were the commonly found microplastic type in lake water and transparent as the dominant color for the two seasons. Almost all the detected microplastic were found to be < 1 mm in size. Due to the small size of microplastic and unavailability of micro-Fourier transform infrared spectroscopy (µ-FTIR) and Raman spectroscopy in Nepal, polymer identification was not done. The findings from this study can provide a valuable baseline data on microplastics for the first time in Nepal's freshwater lake environment.

Adsorption combined with superconducting high gradient magnetic separation technique used for removal of arsenic and antimony.

Manganese iron oxide (MnFe2O4), an excellent arsenic(As)/antimony(Sb) removal adsorbent, is greatly restricted for the solid-liquid separation. Through the application of superconducting high gradient magnetic separation (HGMS) technique, we herein constructed a facility for the in situ solid-liquid separation of micro-sized MnFe2O4 adsorbent in As/Sb removal process. To the relative low initial concentration 50.0µgL-1, MnFe2O4 material sorbent can still decrease As or Sb below US EPA's drinking water standard limit. The separation of MnFe2O4 was mainly relied on the flow rate and the amount of steel wools in the HGMS system. At a flow rate 1Lmin-1 and 5% steel wools filling rate, the removal efficacies of As and Sb in natural water with the system were achieved to be 94.6% and 76.8%, respectively. At the meantime, nearly 100% micro-sized MnFe2O4 solid in the continuous field was readily to be separated via HGMS system. In a combination with the experiment results and finite element simulation, the separation was seemed to be independent on the magnetic field intensity, and the maximum separation capacities in various conditions were well predicted using the Thomas model (R2=0.87-0.99).

The removal efficiency and insight into the mechanism of para arsanilic acid adsorption on Fe-Mn framework.

Para arsanilic acid (p-ASA) is extensively used as feed additives in poultry industry, resulting contaminates soil and natural water sources through the use of poultry litter as a fertilizer in croplands. Thus, removal of p-ASA prior to its entering environments is significant to control their environmental risk. Herein, we studied Fe-Mn framework and cubic Fe(OH)3 as promising novel adsorbents for the removal of p-ASA from aqueous solution. The chemical and micro-structural properties of Fe-Mn framework and cubic Fe(OH)3 materials were characterized by X-ray diffraction patterns (XRD), nitrogen adsorption (SBET), zeta (ζ-) potential, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectra (XPS). The maximum adsorption capacity for p-ASA on Fe-Mn framework and cubic Fe(OH)3 was determined to be 1.3mmolg-1 and 0.72mmolg-1 at pH4.0, respectively. Adsorption of p-ASA decreased gradually with increasing pH indicated that adsorption was strongly pH dependent. Azophenylarsonic acid was identified as an oxidation intermediate product of p-ASA after adsorption on Fe-Mn framework. Plausible removal mechanism for p-ASA by Fe-Mn framework was proposed. The obtained results gain insight into the potential applicability of Fe-Mn framework, which can be potentially important for the removal of p-ASA from water.

Transformation of para arsanilic acid by manganese oxide: Adsorption, oxidation, and influencing factors.

Aromatic organoarsenic compounds tend to transform into more mobile toxic inorganic arsenic via several processes, and can inadvertently spread toxic inorganic arsenic through the environment to water sources. To gain insight into the transformation mechanisms, we herein investigated how the process of para arsanilic acid (p-ASA) transformation works in detail on the surface of adsorbents by comparing it with phenylarsonic acid (PA) and aniline, which have similar chemical structures. In contrast to the values of 0.23 mmol g-1 and 0.68 mmol g-1 for PA and aniline, the maximum adsorption capacity was determined to be 0.40 mmol g-1 for p-ASA at pH 4.0. The results of FTIR and XPS spectra supported the presence of a protonated amine, resulting in a suitable condition for the oxidation of p-ASA. Based on the combined results of UV-spectra and UPLC-Q-TOF-MS, we confirmed that the adsorbed p-ASA was first oxidized through the transfer of one electron from p-ASA on MnO2 surface to form a radical intermediate, which through further hydrolysis and coupling led to formation of benzoquinone and azophenylarsonic acid, which was identified as a major intermediate. After that, p-ASA radical intermediate was cleaved to form arsenite (III), and then further oxidized into arsenate (V) with the release of manganese (Mn) into solution, indicating a heterogeneous oxidation process.

Synthesis of Ce(III)-doped Fe3O4 magnetic particles for efficient removal of antimony from aqueous solution.

Aqueous antimony (Sb) pollution from human activity is of great concern in drinking water due to its adverse health effect. Magnetic Fe3O4 particles, with high separation ability from solution, have been considered as a low-cost Sb adsorbent for contaminants. However, the limited adsorption capacity has restricted its practical application. In this study, a solvothermal approach was developed for doping Ce(III) into Fe3O4, thereby increasing the adsorption efficacy for both Sb(III) and Sb(V). In contrast to un-doped Fe3O4, the adsorption capacity towards Sb(III) and Sb(V) in Ce-doped materials increased from 111.4 to 224.2mg/g and from 37.2 to 188.1mg/g at neutral pH, respectively. Based on the combined results of XPS, XRD, and FTIR, it confirmed that Ce atom successfully doped into the Fe3O4 structure, resulting in the decreased particle size, increased the surface area, and isoelectric point. Furthermore, the vibrating sample magnetometer (VSM) results showed that the Ce doping process had some side effects on the primitive magnetic property, but remaining the high separation potential during water treatment. According to the high removal efficiency and magnetic property, the Ce-doped Fe3O4 of great simplicity should be a promising adsorbent for aqueous Sb removal.