High concentration of antibiotics and their associated ARB and ARGs in the effluent of WWTPs enter the environment through WWTPs discharges to rivers, wastewater reuse, irrigation and amending the soil by biosolids make. Antibiotic resistance genes can persist in the environment even when there is no antibiotic pressure.
Full Answer
Does wastewater treatment contain antibiotic resistant DNA?
The products of wastewater treatment have been found to contain trace amounts of antibiotic resistant DNA. These products are often reintroduced to the environment and water supply, potentially resulting in the spread of antibiotic resistance.
How do antibiotics enter the environment through wastewater treatment plants?
Occurrence of antibiotic resistance in WWTPs High concentration of antibiotics and their associated ARB and ARGs in the effluent of WWTPs enter the environment through WWTPs discharges to rivers, wastewater reuse, irrigation and amending the soil by biosolids make.
How can antibiotic resistance be inactivated in municipal wastewater?
Zhuang Y et al. Inactivation of antibiotic resistance genes in municipal wastewater by chlorination, ultraviolet, and ozonation disinfection. Environmental Science and Pollution Research. May 2015; 22 (9):7037-7044 60. Sharma VK, Johnson N, Cizmas L, McDonald TJ, Kim H.
What happens to antibiotic resistant bacteria after they leave the treatment plant?
In an even more dire scenario, small amounts of antibiotic resistant bacteria and free-floating DNA make it through the filtration membrane and come out the other side of the treatment plant in what is called the effluent, or the water stream that leaves the facility.
How can antibiotic resistance genes be transferred?
Antimicrobial resistance genes are transferred in Gram-negative bacteria through conjugation, and conjugation-mediated transfer of antibiotic resistance genes has been reported in numerous studies [12–14].
Why are antibiotic resistance genes inserted into plant cells?
Some genetically modified plants contain genes that make the plant resistant to certain antibiotics. Scientists often add these resistant genes during genetic modification so that the GM plants and cells can be distinguished from non-GM ones.
How is an antibiotic resistance gene is transferred between bacteria?
Bacteria can share genes with each other in a process called horizontal gene transfer. This can occur both between bacteria of the same species and between different species and by several different mechanisms, given the right conditions.
How do antibiotics enter the environment?
Via toilets, wastewater, and runoff water • Unused antibiotics and antibiotic-containing waste, flushed down drains or toilets, can enter the environment. Antibiotics in manure and other waste-based fertilizers enter waterways along with runoff from crop and grazing fields.
How are genes inserted into plasmids?
Inserting genes into plasmids The piece of DNA or gene of interest is cut from its original DNA source using a restriction enzyme and then pasted into the plasmid by ligation. The plasmid containing the foreign DNA is now ready to be inserted into bacteria. This process is called transformation.
How do scientists insert gene in a bacterium?
Researchers can insert DNA fragments or genes into a plasmid vector, creating a so-called recombinant plasmid. This plasmid can be introduced into a bacterium by way of the process called transformation. Then, because bacteria divide rapidly, they can be used as factories to copy DNA fragments in large quantities.
How does AMR spread?
AMR occurs naturally over time, usually through genetic changes. Antimicrobial resistant organisms are found in people, animals, food, plants and the environment (in water, soil and air). They can spread from person to person or between people and animals, including from food of animal origin.
What is the mechanism of antibiotic resistance?
The main mechanisms of resistance are: limiting uptake of a drug, modification of a drug target, inactivation of a drug, and active efflux of a drug. These mechanisms may be native to the microorganisms, or acquired from other microorganisms.
What is the environmental pressure in the case of antibiotic resistance?
Researchers from Harvard Medical School, Boston Children's Hospital, and the University of Toronto discovered two important environmental factors: temperature and population density. Increases in temperature and population density are associated with antibiotic resistance, and resistance may get stronger over time.
What are the factors that may influence the presence or the absence of antibiotic resistance in a specific environment?
In summary, the 6 main causes of antibiotic resistance have been linked to:Over-prescription of antibiotics.Patients not finishing the entire antibiotic course.Overuse of antibiotics in livestock and fish farming.Poor infection control in health care settings.Poor hygiene and sanitation.More items...•
How do bacteria get on us from the environment?
Microorganisms capable of causing disease—pathogens—usually enter our bodies through the mouth, eyes, nose, or urogenital openings, or through wounds or bites that breach the skin barrier.
What is the most important reservoir of antibiotic resistance in urban environments?
Wastewater is among the most important reservoirs of antibiotic resistance in urban environments. The abundance of carbon sources and other nutrients, a variety of possible electron acceptors such as oxygen or nitrate, the presence of particles onto which bacteria can adsorb, or a fairly stable pH and temperature are examples of conditions favouring the remarkable diversity of microorganisms in this peculiar habitat. The wastewater microbiome brings together bacteria of environmental, human and animal origins, many harbouring antibiotic resistance genes (ARGs). Although numerous factors contribute, mostly in a complex interplay, for shaping this microbiome, the effect of specific potential selective pressures such as antimicrobial residues or metals, is supposedly determinant to dictate the fate of antibiotic resistant bacteria (ARB) and ARGs during wastewater treatment. This paper aims to enrich the discussion on the ecology of ARB&ARGs in urban wastewater treatment plants (UWTPs), intending to serve as a guide for wastewater engineers or other professionals, who may be interested in studying or optimizing the wastewater treatment for the removal of ARB&ARGs. Fitting this aim, the paper overviews and discusses: i) aspects of the complexity of the wastewater system and/or treatment that may affect the fate of ARB&ARGs; ii) methods that can be used to explore the resistome, meaning the whole ARB&ARGs, in wastewater habitats; and iii) some frequently asked questions for which are proposed addressing modes. The paper aims at contributing to explore how ARB&ARGs behave in UWTPs having in mind that each plant is a unique system that will probably need a specific procedure to maximize ARB&ARGs removal.
What is the role of urban wastewater treatment plants?
Urban wastewater treatment plants (UWTPs) have a pivotal role in the protection of the environment, in particular, the natural water bodies. The removal of organic matter, chemical pollutants and undesirable microorganisms from sewage, using combinations of physico-chemical and biological treatments, was a major technological achievement of the last century, allowing the return to the environment of water with good quality. However, the final UWTPs effluents are far from being sterile and, hence, release to the environment high amounts of bacteria, many of which are of animal (e.g. pets or small husbandry or animal farms) or human origin ( Berendonk et al., 2015; Manaia, 2017; Rizzo et al., 2013 ). Many of these bacteria harbour acquired antibiotic resistance genes (ARGs) and are potential carriers for the dissemination of these genes in the environmental microbiome ( Berendonk et al., 2015; Manaia, 2017; Pruden, 2014 ). As such, these bacteria are considered a potential threat to humans and/or animals health since they may lead to more cases of difficult-to-treat infections. Moreover, although only part of the ARB released from UWTP will be able to cause disease in humans or animals, the risk of enriching the environmental resistome either through selection or horizontal gene transfer (HGT), and therefore contribute to the emergence of resistance in pathogenic bacteria cannot be neglected ( Manaia, 2017 ). UWTPs bring together antibiotic resistant bacteria (ARB), antibiotic residues and other potential selectors that favour the selection towards these bacteria and, simultaneously, offer a rich supply of nutrients and close cell-to-cell interaction, capable of facilitating the horizontal transfer of ARGs. These arguments make the UWTPs environment one of the most exciting niches to unveil the fate of ARB&ARGs. This paper is the result of a think tank of Early Stage Researchers summer school organized by the Marie Skłodowska-Curie Innovative Training Networks, project ANSWER ( http://www.answer-itn.eu /), and discusses the tools and the environmental conditions that may rule the fate of ARB&ARGs throughout the wastewater treatment.
What is the fate of Arb&Args?
The study of the fate of ARB&ARGs during wastewater treatment is complex, influenced by a myriad of external factors, difficult to control and monitor in real-world systems. This is probably the reason why we can find contradictory findings in the literature and many unanswered questions, albeit the important efforts researchers around the world have been making. Although researchers did not find a magic formula to study ARB&ARGs in UWTPs, it is now possible to settle some recommendations, which are unanimous among researchers, as it is consensual the evidence that we need a larger body of information to be able to open this black box and maximize the removal of ARB&ARGs during wastewater treatment. Irrespective of the type of methods to use and the plethora of information that can be collected, the establishment of solid hypotheses as a basis for experimental design and the incisive critical thinking on data analyses are essential to advance even more our current knowledge in the field.
Where are sedimentable solids removed?
The remaining sedimentable solids are removed in the primary settling tanks, and channelled into the sludge treatment facilities , whereas the effluent of this primary treatment enters the secondary treatment.
Can microbes be pollutants?
Indeed, microbes that enter, survive or even proliferate during the wastewater treatment can be pollutants themselves if released in the environment, in the sense that they will occur in an environment to which they do not belong, and where they can cause directly or indirectly any kind of damage.
Is wastewater a stressor?
Besides the readily metabolised organic matter, wastewater contains substances that may exert an array of effects on bacteria, being sometimes designated as stressors, of which are examples heavy metals, and recalcitrant natural or synthetic compounds, including antibiotic residues and metabolites thereof.
What bacteria are resistant to antibiotics?
Based on the culture-dependent methods, it was observed that antibiotic-resistant bacterial species most frequently detected in WWTP samples belong to the common indicators of faecal contamination: E. coli, total coliforms, and enterococci. However, in addition to these bacteria, a wide variety of clinically important ARB have been detected, including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp ., and Gram-negative bacteria (e.g. Enterobacteria, Pseudomonas, and Acinetobacter) ( Bouki et al., 2013; Figueira et al., 2011; Goni-Urriza et al., 2000; Zhang et al., 2009b ). Most of the examined enterococci isolates were resistant to many different antibiotics. Amador et al. (2015) reported the resistance to 13 antibiotics in Enterobacteriaceae isolated from WWTP samples. Their results revealed high frequency of resistance to beta-lactams (cefoxitin, amoxicillin/clavulanic acid combination, cefotaxime, aztreonam, cefpirome, ceftazidime) but also to trimethoprim/sulfamethoxazole, tetracycline, and ciprofloxacin. Numerous studies have been conducted on the antimicrobial resistance profile of E. coli originating from WWTPs. High resistance rates were observed for aminopenicillins, sulphonamides, and tetracycline, whereas comparatively lower rates are reported for quinolones ( Ferreira da Silva et al., 2006; Łuczkiewicz et al., 2010 ).
What are the ARGs in wastewater?
Together with antibiotics, antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are introduced into wastewater. Wastewater treatment plants (WWTPs) are believed to be probable hotspots for antibiotic resistance dissemination in the environment as they offer convenient conditions for ARB proliferation as well as for horizontal transfer of ARGs among different microorganisms. In fact, genes conferring resistance to all classes of antibiotics together with mobile genetic elements (MGEs) like plasmids, transposons, bacteriophages, integrons are detected in WWTPs in different countries. It seems that WWTPs with conventional treatment processes are capable of significant reduction of ARB but are not efficient in ARG removal. Implementation of advanced wastewater cleaning processes in addition to a conventional wastewater treatment is an important step to protect the aquatic environment. Growing interest in presence and fate of ARB and ARGs in WWTP systems resulted in the fact that knowledge in this area has increased staggeringly in the past few years. The main aim of the article is to collect and organize available data on ARGs, that are commonly detected in raw sewage, treated wastewater or activated sludge. Resistance to the antibiotics usually used in antibacterial therapy belonging to main classes like beta-lactams, macrolides, quinolones, sulfonamides, trimethoprim and tetracyclines was taken into account. The presence of multidrug efflux genes is also included in this paper. The occurrence of antibiotics may promote the selection of ARB and ARGs. As it is important to discuss the problem considering all aspects that influence it, the levels of antibiotics detected in influent and effluent of WWTPs were also presented.
What is a tetracycline?
Tetracyclines are a group to which both natural (e.g. tetracycline, chlortetracycline, oxytetracycline) and semi-synthetic (e.g. doxycycline, demeclocycline) antibiotics belong. The mechanism of their action is based on inhibition of bacterial protein biosynthesis by binding to the 30S ribosomal subunit and preventing the association of aminoacyl-tRNA ( Yang et al., 2005 ). Currently, they are only occasionally used in human medicine, but they have found widespread application in the treatment of livestock and aquaculture ( Koesukwiwat et al., 2007; Miao et al., 2004; Sczesny et al., 2003 ). Tetracycline, chlortetracycline and oxytetracycline are used for this purpose more often than other antibiotics ( Halling-Sørensen et al., 2003; Jeong et al., 2010; Lopez-Penalver et al., 2010 ). According to literature, >2500 tons of tetracycline in Europe and 1800 tons in the United States are used in veterinary every year ( Halling-Sørensen et al., 2003; Simon, 2005 ). The consumption of tetracyclines for systemic use in the European hospital sector, expressed as the DDD per 1000 inhabitants per day was on the level of 2.0, while the average consumption of this class of antibiotics for systemic use in the community was 0.07 DDD per 1000 inhabitants per day ( ECDC Annual epidemiological report for 2016, 2018 ). After the treatment process, over 70% of tetracycline antibiotics is excreted and released in an active form to the environment by urine or faeces of humans and animals. Due to highly hydrophilic character and low volatility they are very stable in the aquatic environment ( Daghrir and Drogui, 2013 ). This group of compounds, especially tetracycline, is commonly detected in WWTPs. The highest concentration of tetracycline measured in raw sewage was 1300 ng/L ( Gulkowska et al., 2008) and 1100 ng/L ( Batt et al., 2007 ), while in effluent, up to 1420 ng/L of this antibiotic was identified ( Minh et al., 2009 ). The data for oxytetracycline indicated a maximum concentration as 350 ng/L in influent ( Watkinson et al., 2009) and 840 ng/L in purified wastewater ( Minh et al., 2009 ), whereas the highest chlortetracycline detected concentration was 270 ng/L in raw wastewater ( Yang et al., 2005) and 250 ng/L in effluent ( Watkinson et al., 2009 ).
Is Klebsiella pneumoniae untreatable?
Infections caused by pathogens, such as multidrug- resistant Klebsiella pneumoniae and Acinetobacter baumannii, are untreatable with available antibiotics in current medical practice ( McGowan, 2006 ). Generally, there are two mechanisms for the formation of MDR.
Is antibiotic resistance a problem?
Antibiotic resistance is recognized as one of the most important challenges of contemporary medicine and the serious public health problem. This is an extremely dangerous phenomenon, which consequently prevents the effective treatment of bacterial infections and may be the cause of epidemic threats and high mortality. The occurrence of the resistance phenomenon in all species of microorganisms and for each group of antibiotics has been described. Fig. 1 presents the time that has passed since the introduction of individual antibiotics to the observation of appearance of bacteria resistant towards them. Noteworthy is the fact of significant decrease in the number of antibiotics introduced since the 1970s ( Clatworthy et al., 2007 ).
Is hospital wastewater a source of microbial contamination?
Also, adequate management of hospital wastewater, being the main source of microbial contamination, is required. To reduce the dissemination of pathogenic ARB in the environment, initial disinfection of hospital influents is highly recommended.
How does antibiotic resistance spread?
Antibiotic resistance is spreading from wastewater treatment plants. The products of wastewater treatment have been found to contain trace amounts of antibiotic resistant DNA. Researchers have found that even low concentrations of just a single type of antibiotic in the water supply leads to resistance to multiple classes of antibiotics. ...
What is the water stream that leaves a treatment plant?
In an even more dire scenario, small amounts of antibiotic resistant bacteria and free-floating DNA make it through the filtration membrane and come out the other side of the treatment plant in what is called the effluent, or the water stream that leaves the facility.
Where do antibiotics pass through?
The majority of the antibiotics we consume are metabolized in our bodies. However, small amounts pass through us in our waste, which are then carried to wastewater treatment plants. At these plants, one of the common ways in which the wastewater is treated is with a membrane bioreactor, which uses both a filtration system ...
How is resistance passed from parent to daughter cell?
These resistance genes can then be passed on from parent to daughter cell and between neighbors through a process known as horizontal gene transfer. As the bacteria eats, reproduces and grows, an excess is accumulated called biomass. A typical wastewater treatment plant produces tons of biomass every day.
Can plasmids carry resistance genes?
One plasmid may carry resistance genes for several different types of antibiotics, resulting in positive correlations between one type of antibiotic and the resistance gene of another. This not only further complicates things, but can be extremely dangerous.
Can antibiotics be resistant to water?
Researchers have found that even low concentrations of just a single type of antibiotic in the water supply leads to resistance to multiple classes of antibiotics. The products of wastewater treatment have been found to contain trace amounts of antibiotic resistant DNA.
Abstract
Antibiotic resistant bacteria and antibiotic resistance genes have been of the emerging contaminant threatening human health. The overuse of antibiotics, both in human patients and, importantly, in livestock, has led to an explosion of antibiotic-resistant bacteria, both in the U.S. and around the world.
1. Introduction
Antibiotics have been used broadly in the last decades for disease control as well as livestock breeding. The misuse and inappropriate disposal of antibiotics can develop antibiotic resistance bacteria (ARB) and multi-drug resistant bacteria which carry one or more antibiotic resistance genes (ARGs).
2. Occurrence of antibiotic resistance in WWTPs
High concentration of antibiotics and their associated ARB and ARGs in the effluent of WWTPs enter the environment through WWTPs discharges to rivers, wastewater reuse, irrigation and amending the soil by biosolids make. Antibiotic resistance genes can persist in the environment even when there is no antibiotic pressure.
3. Role of WWTP in dissemination of ARG
Freshwater resources are too limited and meeting the needs for water is challenging in the last decades as urban water shortages increase [ 36, 37, 38 ]. Based on the united nations world water development report of UNESCO in 2015, up to 70% of the fresh water, we take from rivers and groundwater is devoted to irrigation [ 38 ].
4. Removal of ARGs and ARB by WWTPs
The effluent of WWTPs is an important source of pollution to the nation’s water resources, and 3.5 million Americans annually are getting sick after touching water they thought was safe [ 52 ]. WWTPs are hotspots for emerging contaminants namely antibiotics, heavy metals, ARGs, and HMRGs [ 32 ].
5. Future developments and perspectives
Antibiotic resistance development among bacteria is a challenging issue that requires improvement of next-generation treatment processes in WWTPs. The emergence of antibiotic resistance between pathogens increases the demand for effective treatment strategies. Knowledge gaps and future research needs are:
Acknowledgments
The authors acknowledge funding support from the Department of Civil and Environmental Engineering, the University of North Carolina at Charlotte.
Where is antibiotic resistance collected?
Antibiotic resistance is a global public health threat. Water from human activities is collected at wastewater treatment plants where processes often do not sufficiently neutralize antibiotic resistant bacteria and genes, which are further shed into the local environment. This protocol outlines the steps to conduct a systematic review based on ...
Is antibiotic resistance in wastewater treatment plants a risk?
Antibiotic resistance in environmental samples around wastewater treatment plants may pose a risk of exposure to workers and nearby residents. Results from the systematic review outlined in this protocol will allow to estimate the extend of exposure, to inform policy making and help to design future studies.
Is antibiotic resistance a global threat?
Antibiotic resistance has become an imminent global public health threat and multiple studies have identified resistant bacteria and resistance genes in environmental samples [ 1, 2 ]. Water resulting from human activities such as agriculture, healthcare services and from the general population is collected at wastewater treatment plants (WWTPs), ...
How do bacteria pass resistance genes?
While consuming the organic waste, the bacteria encounters the antibiotics and expresses resistance genes that reduce effectiveness of these medicines. These resistance genes can then be passed on from parent to daughter cell and between neighbors through a process known as horizontal gene transfer. As the bacteria eats, reproduces and grows, an ...
What is the water stream that leaves a treatment plant?
In an even more dire scenario, small amounts of antibiotic resistant bacteria and free-floating DNA make it through the filtration membrane and come out the other side of the treatment plant in what is called the effluent, or the water stream that leaves the facility.
What is biomass in wastewater?
As the bacteria eats, reproduces and grows, an excess is accumulated called biomass. A typical wastewater treatment plant produces tons of biomass every day. Once treated, it is disposed of in landfills or used as a fertilizer for agriculture and livestock feed crops.
What are the products of wastewater treatment?
The products of wastewater treatment have been found to contain trace amounts of antibiotic resistant DNA. These products are often reintroduced to the environment and water supply, potentially resulting in the spread of antibiotic resistance. As such, researchers at the University of Southern California Viterbi School of Engineering have been studying the development of these potentially harmful and dangerous genes in wastewater treatment processes. Their findings, published in Environmental Science & Technology, indicate that even low concentrations of just a single type of antibiotic leads to resistance to multiple classes of antibiotics.
Where do antibiotics pass through?
The majority of the antibiotics we consume are metabolized in our bodies. However, small amounts pass through us in our waste, which are then carried to wastewater treatment plants. At these plants, one of the common ways in which the wastewater is treated is with a membrane bioreactor, which uses both a filtration system ...
Can plasmids carry resistance genes?
One plasmid may carry resistance genes for several different types of antibiotics, resulting in positive correlations between one type of antibiotic and the resistance gene of another. This not only further complicates things, but can be extremely dangerous. Because of their extremely small size—1,000 times smaller than bacteria—free-floating ...