Health Ethics Draft

heidi

"This power is so easily accessible by labs — you don't need a very expensive piece of equipment and people don't need to get many years of training to do this," says Stanley Qi, a systems biologist at Stanford University in California. "We should think carefully about how we are going to use that power."

wiseman

A conversation about the ethics of human modification has been kicking around since the 1980s, when scientists started using cruder forms of gene editing. "For decades, we've been able to say it's not there yet, so we're not going to do [human gene editing]. It was an easy way to stop the conversation," says Debra Mathews, a bioethicist at Johns Hopkins University. "We're now at a point where it is precise enough that we do actually just have to have the conversation." Over the next three days in DC, scientists and policymakers will have to do just that.

ming

A new strain of red-eyed mutant wasps has been brought into the world by a team of scientists. The wasps were created to prove that CRISPR gene-slicing technology can be used successfully on the tiny parasitic jewel wasps, giving scientists a new way to study some of the wasp's interesting biology, such as how males can convert all their progeny into males by using selfish genetic elements.

rodriguez

Already in 1997 UNESCO issued the Universal Declaration on the Human Genome and Human Rights recommending a moratorium for intervening genetically human germline. In December 2015, the International Summit on Human Gene Editing, which gather members of national scienti c academies of America, Britain and China, discussed the ethics of germline modi cation. ey agreed to proceed further with basic and clinical research under appropriate legal and ethical guidelines, but altering of gametocytes and embryos to generate inheritable changes in humans was claimed irresponsible. In addition, they agreed to initiate an international forum where these concerns will be continuously addressed, and regulations in research harmonized across countries [44]. e US National Institute of Health issued a statement, calling for a moratorium, banning NIH-funded research into genomic editing of human embryos [45].

rodriguez

Another ethical issue to discuss is the possibility of non-therapeutic interventions using genome editing. Its use in germ line is ban for safety reasons. But, the e ciency of CRISPR/Cas9 technique increases the possibility to intervene somatic cells in order to match genetics to our life interests. Many phenotypic characteristics have a genetic component, apart from environment, which could be intervened. For example, the technique could be used to enhance performance of athletes or to prevent violent behaviour or diminish addiction. Generally, gene therapy looks to improve the health of a patient for its own bene t, but it may happens in the future that the criminal justice system mandate genome editing of genes related to violence for repeat o enders or violent dangerous criminals [47]. If the intervention is done during development, there are problems of informed consent with minors, since it is questionable that parents or guardians should be allow to decide for them their future for non-health reasons. Socially, there will be a problem if some populations or individuals may be enhanced genetically having advantage over others, for example in intellectual capacity. Formation of animal chimeras for organ transplantation e development of human/animal chimeras for organ transplantation may provide hope for many that have to wait invaluable time for a human organ donor available. But the formation of these chimeras may carry human neural and germ cells [48]. Chimeras have raised ethical concerns over their risk and on the violation of the order of nature, producing moral confusion on how to treat the organism, as animal or human? [30,49,50]. For some, chimeric embryos possess the potential to develop organisms with human-derived cells or tissue, which may a ect the identity of the human species, a ecting its dignity. But, that an organism contains human cells does not convert the organism into human, neither a ects its dignity. e human like characteristic associated to the chimera are only of biological nature, does not a ect the moral status of the animal, they do not achieve consciousness for example.

otieno

Another question that may arise regarding the embryo genome editing using CRISPR-Cas9 editing technology is the fate of the child produced by such technologies? While it is clear that people's informed consent is secured before genetically engineered somatic cells are used in clinical research, it is not clear what information would be needed from the prospective parents to adequately inform them about the risks involved in germline modi cation [4]. e scienti c community should engage in a dialogue to establish guidelines of research involving genetic modi cation of human germ cells. e discussions should involve stakeholders in di erent elds: the general public, scientists, bioethicists, public policy and legal experts. e discussion should make a clear distinction between genome editing in germ cells and in somatic cells. e signi cant progress being made in clinical development of approaches to cure deleterious diseases should not be impeded by concerns regarding the ethical implications of germline editing [3]. A voluntary moratorium should be called on genetic modi cation of human germ cells. e US National Institute of Health has taken the lead in calling moratorium on genome editing of human embryos. Earlier this year, the director of US National Institutes of Health, Francis Collins issued a statement that banned NIH-funded research into genomic editing of human embryos [16]. Other countries should follow suit. A moratorium has been the kernel of debate among the members of the scienti c community.

heidi

Beyond the farm, researchers are considering how CRISPR could or should be deployed on organisms in the wild. Much of the attention has focused on a method called gene drive, which can quickly sweep an edited gene through a population. The work is at an early stage, but such a technique could be used to wipe out disease-carrying mosquitoes or ticks, eliminate invasive plants or eradicate herbicide resistance in pigweed, which plagues some US farmers. Usually, a genetic change in one organism takes a long time to spread through a population. That is because a mutation carried on one of a pair of chromosomes is inherited by only half the offspring. But a gene drive allows a mutation made by CRISPR on one chromosome to copy itself to its partner in every generation, so that nearly all offspring will inherit the change. This means that it will speed through a population exponentially faster than normal (see 'Gene drive') — a mutation engineered into a mosquito could spread through a large population within a season. If that mutation reduced the number of offspring a mosquito produced, then the population could be wiped out, along with any malaria parasites it is carrying.

heidi

But many researchers are deeply worried that altering an entire population, or eliminating it altogether, could have drastic and unknown consequences for an ecosystem: it might mean that other pests emerge, for example, or it could affect predators higher up the food chain. And researchers are also mindful that a guide RNA could mutate over time such that it targets a different part of the genome. This mutation could then race through the population, with unpredictable effects. "It has to have a fairly high pay-off, because it has a risk of irreversibility — and unintended or hard-to-calculate consequences for other species," says George Church, a bioengineer at Harvard

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CRISPR can be readily adapted to many other organisms

heidi (potential use)

CRISPR's ability to precisely edit existing DNA sequences makes for more-accurate modifications, but it also makes it more difficult for regulators and farmers to identify a modified organism once it has been released. "With gene editing, there's no longer the ability to really track engineered products," says Jennifer Kuzma, who studies science policy at North Carolina State University in Raleigh. "It will be hard to detect whether something has been mutated conventionally or genetically engineered."

selle

CRISPR-Cas systems actually provide adaptive immunity in bacteria, and have much promise for various applications in food bacteria that include high-resolution typing of pathogens, vaccination of starter cultures against phages, and the genesis of programmable and specific antibiotics that can selectively modulate bacterial population composition. Indeed, the molecular machinery from these DNA-encoded, RNA-mediated, DNA-targeting systems can be harnessed in native hosts, or repurposed in engineered systems for a plethora of applications that can be implemented in all organisms relevant to the food chain, including agricultural crops trait-enhancement, livestock breeding, and fermentation-based manufacturing, and for the genesis of next-generation food products with enhanced quality and health-promoting functionalities. CRISPR-based applications are now poised to revolutionize many fields within food science, from farm to fork.

otieno

CRISPR-Cas9 genome editing technology to an embryo is a very risky a air. Researchers may not be in a position to determine, with precision, the e ect of such procedures before birth. Lanphier opines that the quality control can be performed only on a subset of cells. is limitation shows that it may be impossible to know the e ect of genetic modi cation of an embryo with precision until a er birth. Even then, potential problems may take years to surface [4].

christopher

CRISPR/Cas9 has seen a meteoric rise during the past 2 years, with appli- cations to bacterial, animal, human, and, most recently, plant systems (Pennisi, 2013). This is due, in part, to a greater number of advantages of CRISPR/Cas9, includ- ing the straightforward construct design and assembly, as compared with zinc finger nucleases and TALENs.

kaiser

Chinese researchers report this week that they have used the CRISPR gene-editing technique to modify the genome of a human embryo in an effort to make it resistant to HIV infection

How the DNA Revolution Is Changing Us

Combating the Ae. aegypti mosquito, which carries so many different pathogens, would require a slightly different approach. "What you would need to do," he told me, "is engineer a gene drive that makes the insects sterile. It doesn't make sense to build a mosquito resistant to Zika if it could still transmit dengue and other diseases." To fight off dengue, James and his colleagues have designed CRISPR packages that could simply delete a natural gene from the wild parent and replace it with a version that would confer sterility in the offspring. If enough of those mosquitoes were released to mate, in a few generations (which typically last just two or three weeks each) entire species would carry the engineered version. James is acutely aware that releasing a mutation designed to spread quickly through a wild population could have unanticipated consequences that might not be easy to reverse. "There are certainly risks associated with releasing insects that you have edited in a lab," he said. "But I believe the dangers of not doing it are far greater."

First CRISPR single-nucleotide edited transgenic mice

Cystic fibrosis, sickle cell anemia, Huntington's disease and phenylketonuria are all examples of disorders caused by the mutation of a single nucleotide, a building block of DNA. The human DNA consists of approximately 3 billion nucleotides of four types: Adenine (A), cytosine (C), guanine (G), and thymine (T). In some cases, the difference of just one nucleotide can bring serious consequences. Scientists hope to cure these diseases by substituting the incorrect nucleotide with the correct one.

otieno

Genome editing in human embryos using CRISPR-Cas9 could have unpredictable e ects to the future generations. CRISPR-Cas9 technology could be used for non-therapeutic modi cations [4]. is procedure will open the door to the loss of human diversity and eugenics [13]. Last year, Yoshimi et al., successfully changed the coat colour of the rat suggesting the possibility of inducing a pigmentation change in humans through embryonic editing [14]. So, the genetic enhancement of a speci c appearance could cause substantial physical and mental health to the children since their appearance is imposed on them through means other than blood relationship [14]

otieno

Genome editing of the human embryo could hinder the ongoing research that involve gene editing of somatic cells that hold promise for therapeutic development. As rightly pointed out by Edward Lanphier et al [4], the public outcry about the ethical breach of human embryo genome editing could hinder the promising area of therapeutic development that are involved in making genetic changes in somatic cells. And there should be an open discussion around the appropriate action should a compelling case arise for therapeutic bene t of germline modi cation [4].

heidi

In the past few years, researchers have used the method to engineer petite pigs and to make disease-resistant wheat and rice. They have also made progress towards engineering dehorned cattle, disease-resistant goats and vitamin-enriched sweet oranges. Doudna anticipates that her list of CRISPR-modified organisms will grow. "There's an interesting opportunity to consider doing experiments or engineering pathways in plants that are not as important commercially but are very interesting from a research perspective — or for home vegetable gardens," she says.

heidi

Last year, bioengineer Daniel Anderson of the Massachusetts Institute of Technology in Cambridge and his colleagues used CRISPR in mice to correct a mutation associated with a human metabolic disease called tyrosinaemia5. It was the first use of CRISPR to fix a disease-causing mutation in an adult animal — and an important step towards using the technology for gene therapy in humans (see 'A brief history of CRISPR'). The idea that CRISPR could accelerate the gene-therapy field is a major source of excitement in scientific and biotechnology circles. But as well as highlighting the potential, Anderson's study showed how far there is to go. To deliver the Cas9 enzyme and its guide RNA into the target organ, the liver, the team had to pump large volumes of liquid into blood vessels — something that is not generally considered feasible in people. And the experiments corrected the disease-causing mutation in just 0.4% of the cells, which is not enough to have an impact on many diseases.

heidi

Medical geneticist James Wilson of the University of Pennsylvania in Philadelphia was at the centre of booming enthusiasm over gene therapy in the 1990s — only to witness its downfall when a clinical trial went wrong and killed a young man. The field went into a tailspin and has only recently begun to recover. The CRISPR field is still young, Wilson says, and it could be years before its potential is realized. "It's in the exploration stage. These ideas need to ferment."

cai

More recently, this technology has been increasingly applied to the study or treatment of human diseases, including Barth syndrome effects on the heart, Duchenne muscular dystrophy, hemophilia, β-Thalassemia, and cystic fibrosis. CRISPR/Cas9 (CRISPR-associated protein 9) genome editing has been used to correct disease-causing DNA mutations ranging from a single base pair to large deletions in model systems ranging from cells in vitro to animals in vivo. In addition to genetic diseases, CRISPR/Cas9 gene editing has also been applied in immunology-focused applications such as the targeting of C-C chemokine receptor type 5, the programmed death 1 gene, or the creation of chimeric antigen receptors in T cells for purposes such as the treatment of the acquired immune deficiency syndrome (AIDS) or promoting anti-tumor immunotherapy. Furthermore, this technology has been applied to the genetic manipulation of domesticated animals with the goal of producing biologic medical materials, including molecules, cells or organs, on a large scale. Finally, CRISPR/Cas9 has been teamed with induced pluripotent stem (iPS) cells to perform multiple tissue engineering tasks including the creation of disease models or the preparation of donor-specific tissues for transplantation.

heidi

People just don't have the time to characterize some of the very basic parameters of the system," says Bo Huang, a biophysicist at the University of California, San Francisco. "There is a mentality that as long as it works, we don't have to understand how or why it works." That means that researchers occasionally run up against glitches. Huang and his lab struggled for two months to adapt CRISPR for use in imaging studies. He suspects that the delay would have been shorter had more been known about how to optimize the design of guide RNAs, a basic but important nuance.

Ethical challenges of genome editing

Professor Karen Yeung, Director of the Centre for Technology, Law & Society at King's and a member of the Nuffield Council on Bioethics Working Group, who conducted the review said: 'We examined the way in which these technologies are being taken up in the research community and what we found is that, because of a number of advantages which they offer in relation to existing techniques for manipulating DNA, they are having an unprecedented transformative effect on the biological sciences and for that reason they have the potential to change our expectations and ambitions about human control over the biological world.

otieno

Some scientists argue that there is no need for a moratorium. John Harris, a bioethicist at the University of Manchester, UK is in support of the Huang's research on genetic modi cation of human germ cells using CRISPR-Cas9 genome editing technology. Since Huang and his team of researchers avoided ethical concerns that their research could have generated by using non-viable embryos that could not have led to a live birth, John Harris applauds the research arguing that it is no worse than what happens frequently in IVF where non-viable embryos are discarded. erefore, he does not see the need for justi cation on moratorium [17]. Supporting the CRISPR-Cas9 human germline editing, Linzhao Cheng, a professor at Johns Hopkins University, argues: "Many people are concerned that we shouldn't be doing this, even in abnormal embryos that would be arrested at the blastocyst stage [as was the case here] and otherwise would be discarded. If many people have deep concerns about doing it even in non-viable embryos then how will we ever nd out whether using a normal embryo would be better or worse?" [18]. Other scientists have argued that modi cation of germline cells could be justi able if its purpose is solely for research. George Daley, a stem-cell biologist at Harvard Medical School in Boston, Massachusetts, succinctly points out that scienti c research done using CRISPR-Cas9 and other genome editing tools in human germline cells could provide answers to many scienti c questions, which are not related to clinical applications [17]. According to Harris, the side e ects of germline editing should not be used as a justi cation to call a moratorium on genetic modi cation of human germ cells. It may be ethically justi able to make the technique available in clinics. He argues that the genetic disease may be worse than the side e ects because people with genetic disease will go on reproducing [17] and their progeny stand a higher chance of inheriting the defective gene responsible for a genetic disorder.

waikel

Superbugs—bacterial strains that are resistant to several types of antibiotics—have become an increasingly serious health concern. The Centers for Disease Control and Prevention (CDC) in the United States reports that at least 2 million Americans become ill with antibiotic-resistant infections annually, with more than 23,000 of these cases resulting in death. Resistance results from the overuse and misuse of antibiotics and from the ability of the infecting bacteria to acquire resistance genes

Genome Editing Poses Ethical Problems That We Cannot Ignore

The concern prompting the US academics' call for a moratorium is the potential for altering the human germ-line, making gene alterations inheritable by our children. Gene therapies that produce non-inheritable changes in a person's genome are ethically accepted, in part because there is no risk for the next generation if things go wrong. However to date only one disease - severe combined immunodeficiency - has been cured by this therapy. Germ-line alternations pose much greater ethical concerns. A mistake could harm future individuals by placing that mistake in every cell. Of course the flip-side is that, if carried out safely and as intended, germ-line alterations could also provide potentially permanent solutions to genetic diseases. No research is yet considering this in humans, however. Nevertheless, even if changes to the germ-line turn out to be safe, the underlying ethical concerns of scope and scale that genome editing brings will remain. If a technique can be used widely and efficiently, without careful oversight governing its use, it can readily become a new norm or an expectation. Those unable to access the desired genetic alterations, be they humans with diseases, humans without enhanced genetic characteristics, or farmers without genetically modified animals or crops, may all find themselves gravely and unfairly disadvantaged.

christopher

The first reports of CRISPR/Cas9 editing in plants appeared in 2013, with successful application for both transient expression and recovery of stable transgenic lines. In addition to demonstration of the efficacy in the models Arabidopsis (Arabidopsis thaliana ; Li et al., 2013) and Nicotiana benthamiana (Nekrasov et al., 2013), there have also been reports for three crop species, rice ( Oryza sativa; Zhang et al., 2014), sorghum ( Sorghum bicolor ; Jiang et al., 2013), and wheat (Triticum aestivum ; Wang et al., 2014). For stable transgenic lines, modifications reported for genes in primary transformants of Arab- idopsis and rice were shown to persist into the next generation (Feng et al., 2014; Zhang et al, 2014). Thus, CRISPR/Cas9 is rapidly becoming the tool of choice for gene editing in plants, but further testing is needed to determine whether efficacy will be universal.

scientists debate

The reason CRISPR is so controversial is that it works well on mammalian"germline" cells, such as sperm, eggs and embryonic cells, and the genetic editing can therefore result in heritable traits. Baltimore said he hopes the final session Thursday will produce recommendations for a path forward.

First CRISPR single-nucleotide edited transgenic mice

The scientists tested the CRISPR-nCas9-cytidine deaminase fusion in mice by changing a single nucleotide in the dystrophin gene (Dmd) or the tyrosinase gene (Tyr). They were successful in both cases: Embryos with the single nucleotide mutation in the Dmd gene led to mice producing no dystrophin protein in their muscles, and mice with the Tyr mutation showed albino traits. Dystrophin is indeed connected with the muscular dystrophin disease and tyrosinase controls the production of melanine. Moreover, these single-nucleotide substitutions appeared only in the target position. This is important because it means that only the correct nucleotide is substituted. "We showed here for the first time that programmable deaminases efficiently induced base substitutions in animal embryos, producing mutant mice with disease phenotypes. This is a proof-of-principle experiment. The next goal is to correct a genetic defect in animals. Ultimately, this technique may allow gene correction in human embryos," expressed KIM Jin-Soo, Director of the Center and leading author of this study.

marcus

There are those who believe that given the importance of the ethical debate, the more people know about Crispr—including hands-on experience with it—the better. A do-it-yourself Crispr kit with enough material to perform five experiments gene-editing the bacteria included in the package is available online for $150. Genspace, the Brooklyn, N.Y., community lab where Mr. Sadeghi is learning how to use Crispr to edit a gene in brewer's yeast, charges $400 for four intensive sessions. More than 80 people have taken the classes since the lab started offering them last year. Both the kit and the lab allow people to work only on harmless organisms. And Genspace is an example of the kind of educational program that many researchers are racing to develop—not just explaining how to use the technology but also discussing when and how it should be used. That discussion continues to bubble at the highest levels, as scientists wrestle with what limits should be imposed on Crispr inside their labs. A scientific advisory committee set up by the National Academy of Sciences and the National Academy of Medicine issued a report this month that supports human genome editing to try to treat and prevent diseases, but says more public discussion is needed for other uses, such as editing genes in eggs, sperm or embryos, which could be passed on to future offspring.

heidi

Total cost: as little as $30. "That effectively democratized the technology so that everyone is using it," says Haber. "It's a huge revolution."

heidi

Under existing rules, not all crops made by genome editing would require regulation by the US Department of Agriculture (see Nature 500, 389-390; 2013). But in May, the agriculture department began to seek input on how it can improve regulation of genetically modified crops — a move that many have taken as a sign that the agency is re-evaluating its rules in light of technologies such as CRISPR. "The window has been cracked," says Kuzma. "What goes through the window remains to be seen. But the fact that it's even been cracked is pretty exciting."

hieid

While Anderson and others are aiming to modify DNA in human cells, others are targeting crops and livestock. Before the arrival of gene-editing techniques, this was generally done by inserting a gene into the genome at random positions, along with sequences from bacteria, viruses or other species that drive expression of the gene. But the process is inefficient, and it has always been fodder for critics who dislike the mixing of DNA from different species or worry that the insertion could interrupt other genes. What is more, getting genetically modified crops approved for use is so complex and expensive that most of those that have been modified are large commodity crops such as maize (corn) and soya beans.

otieno

While CRISPR-Cas9 genome editing technology holds promise to personalized medicine, human genetic modi cation and the development of new drugs, the technology has raised caution ags. Genome editing technology is a cautionary tale. We can easily get caught up in the glamour of scienti c and technological advancement while at the same time oblivious to the ethical rami cation of such scienti c and technological advancement. Some scientists have expressed concern that human germline editing has not only crossed the ethical redline; it is also fraught with many challenges. e recent research by Chinese scientists using CRISPR-Cas9 to edit the embryo genome was not completely successful. So, it had to be abandoned at its preliminary stage. ere were o -target mutations in the genome. ese o -target mutations can be deleterious as they can cause cell death and transformation. Consequently, embryo germline editing could be exploited in non-therapeutic research. For instance, it can be used to produce designer babies by eliminating undesired qualities and replacing them with desired ones. However, genome editing Page 3 of 3 technology should not hinder the promising area of therapeutic development that are involved in making genetic changes in somatic cells. Due to the challenges and ethical concerns raised by CRISPR- Cas9 genome editing technology, a temporary moratorium should be called on the technology to allow the scienti c community and other stakeholders to engage in a broad-based discussion to map the way forward for this technology.

otieno

While some members of the scienti c community have argued that a moratorium should be called on human genome editing [9], others have argued that it is unethical to withhold a technology that would eliminate devastating genetic diseases, such as cystic brosis [10]. e Chinese researchers who used CRISPR-Cas9 genome editing technology to eradicate the human β-globulin (HBB) gene from the germline of the human embryo were confronted with some challenges, which made them to stop the research prematurely.

heidi

With so many unanswered questions, it is important to keep expectations of CRISPR under control, says Katrine Bosley, chief executive of Editas, a company in Cambridge, Massachusetts, that is pursuing CRISPR-mediated gene therapy. Bosley is a veteran of commercializing new technologies, and says that usually the hard part is convincing others that an approach will work. "With CRISPR it's almost the opposite," she says. "There's so much excitement and support, but we have to be realistic about what it takes to get there."

wiseman

With these improvements, Harvard geneticist George Church estimates that Crispr's error rate, best-case scenario, could be just 1 in 300 trillion letters of DNA. (The rate can vary quite widely in different types of cells and with different guide RNA designs.) Even at the higher end, that's comparable to the spontaneous mutation rate in humans, says Church.

heidi

began at a meeting in 2014, when she saw a postdoc present work in which a virus was engineered to carry the CRISPR components into mice. The mice breathed in the virus, allowing the CRISPR system to engineer mutations and create a model for human lung cancer4. Doudna got a chill; a minor mistake in the design of the guide RNA could result in a CRISPR that worked in human lungs as well. "It seemed incredibly scary that you might have students who were working with such a thing," she says. "It's important for people to appreciate what this technology can do."

otieno

e cost of germline editing technology is very high to the extent that families coming from rich countries could a ord it. e developing countries will not be in a position to a ord the cost of this technology. is may confer an advantage to children born in developed countries. -price cheap enough for developing countries to develop treatments(universalisability)

christopher

economic impor- tance (fresh and processed), which in the United States alone accounts for more than $2 billion

rodriguez

erefore, the genomic editing of human embryos for therapeutic reasons is being hold so far. e risks of hereditable unpredictable genetic mutations are greater than the possible bene ts of therapy, a ecting the principle of non-male cence. e technique should be fully safe in order to try therapy in the germline. Furthermore, if damage were introduced, there will be a problem to whom make liable for the damage for following generations. Once genome editing reaches enough safety level to allow clinical applications for preventing the development of genetic diseases, further discussion will be needed, considering social, legal and ethical implications and the need of regulatory norms to avoid abuses of germline genome editing.

kaiser

modify the CCR5 gene, which codes for a cell receptor that the HIV virus uses to enter T cells. The researchers used flawed embryos that were not viable for fertility treatments and destroyed them after 3 days.

waikel

the bacterial family of carbapenem-resistant Enterobacteriaceae (CRE) is now one of the greatest threats to human health, with mortality rates approaching 50% according to the CDC. The increases in cases of MRSA and CRE have prompted the need to find alternative antimicrobial approaches. One promising antimicrobial tool is the use of CRISPR-Cas (clustered regularly interspaced short palindromic repeats and associated proteins) genome editing to either kill resistant bacteria or eradicate antibiotic resistance and virulence genes.

Auer

usefulness of CRISPR/Cas9 compared to previous methods of genome editing such as using zinc finger nucleases, in that the CRISPR method is more efficient and easier to construct to make the desired nucleotide changes in a gene