Carbapenemase and extended-spectrum β-lactamase producing bacteria isolated from municipal wastewater treatment plant and urban river in Nepal

Emission and dispersal of antibiotic resistance genes through bioaerosols generated during the treatment of municipal sewage

Promising bioprocesses for the efficient removal of antibiotics and antibiotic-resistance genes from urban and hospital wastewaters: Potentialities of aerobic granular systems

Background:Human exposure to antibiotic resistant bacteria (ARB) is a public health concern which could occur in a number of ways. Wastewaters seem to play an important role in the dissemination of bacteria and antibiotic resistant genes (ARGs) in our environment. The aim of this study was to evaluate the occurrence of three groups of ARB and their resistance genes in hospital and municipal wastewaters (MWs) as possible sources.Methods:A total of 66 samples were collected from raw MWs and hospital wastewaters (HWs) and final effluents of related wastewater treatment plants (WWTPs). Samples were analyzed for the detection of three groups of ARB including gentamicin (GM), chloramphenicol (CHL) and ceftazidime resistant bacteria and their ARGs (aac (3)-1, cmlA1 and ctx-m-32, respectively).Results:The mean concentration of GM, CHL and ceftazidime resistant bacteria in raw wastewater samples was 1.24 × 107, 3.29 × 107 and 5.54 × 107 colony forming unit/100 ml, respectively. There is a variation in prevalence of different groups of ARB in MWs and HWs. All WWTPs decreased the concentration of ARB. However, high concentration of ARB was found in the final effluent of WWTPs. Similar to ARB, different groups of ARGs were found frequently in both MWs and HWs. All genes also detected with a relative high frequency in effluent samples of MWs WWTPs.Conclusions:Discharge of final effluent from conventional WWTPs is a potential route for dissemination of ARB and ARGs into the natural environment and poses a hazard to environmental and public health.

Metagenomic analysis of bacterial community composition and antibiotic resistance genes in a wastewater treatment plant and its receiving surface water

Waterborne disease is a global burden, which is mainly caused by waterborne pathogens disseminated through unsafe water, inadequate sanitation, and hygiene. Antibiotic resistance, which can also spread in water, has become an increasingly serious global health threat as it can prevent the effective treatment of infectious diseases. Improvements on water treatment and detection are the two critical strategies to control the surveillance of waterborne pathogens as well as antibiotic resistance bacteria and genes. The advancement in photo- and electro-chemical methods may provide more opportunities on decentralized water treatment and on-site pathogen monitoring under source-limited conditions. This thesis is dedicated to exploring the possible solutions to automatic, rapid, and easy-to-use in situ pathogen analysis for environmental water by adopting photo- or electro-chemical method, and to enhanced removal of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) from wastewater by combining photo- and electro-chemical techniques. These include removal of ARB and ARGs by UV-assisted electrochemical treatment, electrochemical cell lysis (ECL) for DNA extraction from bacteria, and sunlight-activated propidium monoazide (PMA) pretreatment for live/dead bacteria differentiation by quantitative real-time polymerase chain reaction (qPCR) detection. Both experimental approaches and computational modelling were used to evaluate the performance of the techniques and to bring more insights into the mechanism. Each study presents a demonstration on real environmental or wastewater to access the potential of their applications under complex environmental parameters. UV-assisted electrochemical treatment for ARB and ARGs was conducted using a blue TiO₂ nanotube array (BNTA) anode. The inactivation of tetracycline- and SMX-resistant E. coli and the corresponding plasmid coded genes (tetA and sul1) damage was measured by plate counting on selective agar and qPCR, respectively. As a comparison of UV treatment alone, the enhanced reduction of both ARB and ARGs was achieved by UV-assisted electrochemical oxidation (UV-EO) without Cl⁻ and was further facilitated with the presence of Cl⁻, which is attributed to the in-situ generated oxidants by electrochemical process. Significantly slower removal of ARG than ARB was observed for both UV irradiation alone and UV-EO treatment, wherein intracellular ARG generally reduced slower than extracellular ones, and short amplicons reduced significantly slower than long ones. The predominant nucleotide damage by UV irradiation and conformational change by UV-EO treatment was visualized by DNA gel electrophoresis for treated extracellular ARGs. The mechanism on ARB and ARGs damage was further understood by computational chemical modeling. The slower reduction was found for the native bacteria and genes, tetA and sul1, in the latrine wastewater than that in laboratory-prepared buffered samples. The result emphasizes that all the UV-based techniques may only apply after other treatments to avoid the impairment by the transmittance, color, and particulate material in environmental or wastewater. A comprehensive investigation was conducted for ECL in terms of its performance on DNA extraction from gram-negative bacteria (Escherichia coli and Salmonella Typhi) and gram-positive bacteria (Enterococcus durans and Bacillus subtilis). A milliliter-output ECL device was developed based on the disruption of the cell membrane by OH⁻ that can be generated locally at the cathode and accumulated improvingly through a cation exchange membrane. Both gram-negative and gram-positive bacteria were successfully lysed within 1 min at a low voltage of ~5 V. To better understand the pH effects on cell lysis, the pH profile at the cathode surface and in bulk cathodic effluent was simulated via hydroxide transport in the cathodic chamber. The demonstration of ECL on various environmental water sample types (including pond water, treated wastewater, and untreated wastewater) showed its potential as a prelude to nucleic-acid based analyses of waterborne bacteria in the field. Propidium monoazide (PMA), a nucleic acid-binding dye, has been used to distinguish live from dead cells prior to PCR-based detection. To explore the off-the-grid application of PMA, sunlight was investigated for PMA activation as an alternative light source to a typical halogen lamp. PMA was successfully activated by a solar simulator, and the pretreatment conditions were optimized with respect to the PMA concentration as 80 µM and the exposure time as 10 min. The optimal PMA pretreatment was tested on four different bacteria species (two gram-positive and two gram-negative), and the effects of sunlight intensity and multi-sequential treatment were studied. Sunlight-activated PMA pretreatment was eventually demonstrated on latrine wastewater samples with natural sunlight on both sunny and cloudy days. The results showed the potential of sunlight-activated PMA pretreatment to be integrated into a lab-on-a-chip (LOAC) PCR device for off-the-grid microbial detection and quantification.

Drinking water sources as hotspots of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs): Occurrence, spread, and mitigation strategies

The prevalence of drug-resistant and virulent Staphylococcus spp. in a municipal wastewater treatment plant and their spread in the environment

Antibiotics and antibiotic resistant genes (ARGs) in groundwater: A global review on dissemination, sources, interactions, environmental and human health risks

Small-scale wastewater treatment plants as a source of the dissemination of antibiotic resistance genes in the aquatic environment

Abundance of antibiotic resistance genes in five municipal wastewater treatment plants in the Monastir Governorate, Tunisia

Fate of antibiotic resistant cultivable heterotrophic bacteria and antibiotic resistance genes in wastewater treatment processes

Occurrence and fate of antibiotics, antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) in municipal wastewater treatment plant: An overview

Quantitative and qualitative changes in antibiotic resistance genes after passing through treatment processes in municipal wastewater treatment plants

Antibiotic resistant bacteria and genes (ARB and ARG) in water and sewage treatment units: A review

Synergistic effect of UV/chlorine in bacterial inactivation, resistance gene removal, and gene conjugative transfer blocking