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Posts about bacteria, antibiotics, microbes, and the overuse of antibiotics. See also health care related posts.
Recommended posts: How do antibiotics kill bacteria? - CDC Urges Increased Effort to Reduce Drug-Resistant Infections - Entirely New Antibiotic Developed - Antibiotic Discovery Stagnates - Antibiotics Too Often Prescribed for Sinus Woes
Related: Articles on the overuse of antibiotics - Antibiotic Resistance and You

People are Superorganisms With Microbiomes of Thousands of Species

In a recent article in National Geographic Carl Zimmer has again done a good job of explaining the complex interaction between our bodies and the bacteria and microbes that make us sick, and keep us healthy.

The damage done by our indiscriminate use of antibiotics is not just the long term resistance that we create in bacteria (making the future more dangerous for people) that I have written about numerous times but it also endangers the person taking the anti-biotics in the short term. Sometimes the other damage is a tradeoff that should be accepted. But far too often we ignore the damage taking antibiotics too often does.

When You Swallow A Grenade

While antibiotics can discriminate between us and them, however, they can’t discriminate between them and them–between the bacteria that are making us sick and then ones we carry when we’re healthy. When we take a pill of vancomycin, it’s like swallowing a grenade. It may kill our enemy, but it kills a lot of bystanders, too.

If you think of the human genome as all the genes it takes to run a human body, the 20,000 protein-coding genes found in our own DNA are not enough. We are a superorganism that deploys as many as 20 million genes.

Before he started taking antibiotics, the scientists identified 41 species in a stool sample. By day 11, they only found 13. Six weeks after the antibiotics, the man was back up to 38 species. But the species he carried six weeks after the antibiotics did not represent that same kind of diversity he had before he took them. A number of major groups of bacteria were still missing.

They found that children who took antibiotics were at greater risk of developing inflammatory bowel disease later in life. The more antibiotics they took, the greater the risk. Similar studies have found a potential link to asthma as well.

The human body contains trillions of microorganisms — outnumbering human cells by 10 to 1. Because of their small size, however, microorganisms make up only about 1% to 3% of the body’s mass, but play a vital role in human health.

Where doctors had previously isolated only a few hundred bacterial species from the body, Human Microbiome Project (HMP) researchers now calculate that more than 10,000 microbial species occupy the human ecosystem. Moreover, researchers calculate that they have identified between 81% and 99% of all microorganismal genera in healthy adults.

“Humans don’t have all the enzymes we need to digest our own diet,” said Lita Proctor, Ph.D., NHGRI’s HMP program manager. “Microbes in the gut break down many of the proteins, lipids and carbohydrates in our diet into nutrients that we can then absorb. Moreover, the microbes produce beneficial compounds, like vitamins and anti-inflammatories that our genome cannot produce.” Anti-inflammatories are compounds that regulate some of the immune system’s response to disease, such as swelling.

“Enabling disease-specific studies is the whole point of the Human Microbiome Project,” said Barbara Methé, Ph.D., of the J. Craig Venter Institute, Rockville, MD, and lead co-author of the Nature paper on the framework for current and future human microbiome research. “Now that we understand what the normal human microbiome looks like, we should be able to understand how changes in the microbiome are associated with, or even cause, illnesses.”

Read the full NIH press release on the normal bacterial makeup of the body

Related: Tracking the Ecosystem Within UsWhat Happens If the Overuse of Antibiotics Leads to Them No Longer Working?Antibacterial Products May Do More Harm Than GoodAntibiotics Too Often Prescribed for Sinus Woes

Antibiotics fuel obesity by creating microbe upheavals

Antibiotics fuel obesity by creating microbe upheavals

We aren’t single individuals, but colonies of trillions. Our bodies, and our guts in particular, are home to vast swarms of bacteria and other microbes. This “microbiota” helps us to harvest energy from our food by breaking down the complex molecules that our own cells cannot cope with. They build vitamins that we cannot manufacture. They ‘talk to’ our immune system to ensure that it develops correctly, and they prevent invasions from other more harmful microbes. They’re our partners in life.

What happens when we kill them?

Farmers have been doing that experiment in animals for more than 50 years. By feeding low doses of antibiotics to healthy farm animals, they’ve found that they could fatten up their livestock by as much as 15 percent.

Ilseung Cho from the New York University School of Medicine has confirmed that hypothesis. By feeding antibiotics to young mice, he has shown that the drugs drastically change the microscopic communities within their guts, and increase the amount of calories they harvest from food. The result: they became fatter.

I continue to believe we are far to quick to medicate. We tremendously overuse anti-biotis and those costs are huge. They often are delays and systemic and given our current behavior we tend to ignore delayed and systemic problems.

The link between the extremely rapid rise in obesity and the overuse of anti-biotics is in need of much more study. It seems a possible contributing factor but there is much more data needed to confirm such a link. And other factors still seem dominant to me: increase in caloric intake and decrease in physical activity.

Related: Science Continues to Explore Causes of Weight GainWaste from Gut Bacteria Helps Host Control WeightHealthy Diet, Healthy Living, Healthy WeightRaising Our Food Without Antibiotics

Our Dangerous Antibiotic Practices Carry Great Risks

Our continued poor antibiotics practices increase the risk of many deaths. We are very poor at reacting to bad practices that will kill many people in the future. If those increased deaths happened today it is much more likely we would act. But as it is we are condemning many to have greatly increased odds of dying from bacterial causes that could be prevented if we were more sensible.

Resistance to antibiotics is becoming a crisis

Increasingly, microbes are becoming untreatable. Margaret Chan, director general of the World Health Organization, warned in March of a dystopian future without these drugs. “A post-antibiotic era means, in effect, an end to modern medicine as we know it,” she said. “Things as common as strep throat or a child’s scratched knee could once again kill.”

evidence is mounting that antibiotics are losing efficacy. Through the relentless process of evolution, pathogens are evading the drugs, a problem known broadly as antimicrobial resistance.

Europe has launched a $741 million, seven-year, public-private collaborative research effort to accelerate drug development.

Seeking new antibiotics is wise but the commentary completely ignores our bad practices that are causing the problem to be much worse than it would be if we acted as though bad practices that will lead to many deaths should be avoided.

Previous posts about practices we taking that create great risk for increased deaths: Antibiotics Too Often Prescribed for Sinus Woes (2007)Meat Raised Without Antibiotics is Sadly Rare Today (2007)Overuse of Antibiotics (2005)CDC Urges Increased Effort to Reduce Drug-Resistant Infections (2006)FDA May Make Decision That Will Speed Antibiotic Drug Resistance (2007)Antibacterial Soaps are Bad (2007)Waste Treatment Plants Result in Super Bacteria (2009)Antibiotics Breed Superbugs Faster Than Expected (2010)Antibiotics Use in Farming Can Create Superbugs (2010)What Happens If the Overuse of Antibiotics Leads to Them No Longer Working? (2011)Dangerous Drug-Resistant Strains of TB are a Growing Threat (2012)

Obviously bacteria evolve to survive the counter measures we currently have. The foolish practices of promoting ignorance of evolution leads to a society where the consequences of actions, and the presence of evolution, lead to bad consequences. We find ourselves in that society.

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Bacteria In Cave Isolated for 4 Million Years Highly Resistant to Many Antibiotics

PLoS published an interesting open access research paper on bacteria and their resistance to antibiotics. I am surprised how widespread and strong the antibiotic resistance was is the isolated bacteria that were studied. It raises more interesting questions about the important area of antibiotics.

The lead researcher on this study, Gerry Wright, previously published on antibiotic properties of bacteria found in soil.

Abstract of Antibiotic Resistance Is Prevalent in an Isolated Cave Microbiome

Antibiotic resistance is a global challenge that impacts all pharmaceutically used antibiotics. The origin of the genes associated with this resistance is of significant importance to our understanding of the evolution and dissemination of antibiotic resistance in pathogens. A growing body of evidence implicates environmental organisms as reservoirs of these resistance genes; however, the role of anthropogenic use of antibiotics in the emergence of these genes is controversial.

We report a screen of a sample of the culturable microbiome of Lechuguilla Cave, New Mexico, in a region of the cave that has been isolated for over 4 million years. We report that, like surface microbes, these bacteria were highly resistant to antibiotics; some strains were resistant to 14 different commercially available antibiotics. Resistance was detected to a wide range of structurally different antibiotics including daptomycin, an antibiotic of last resort in the treatment of drug resistant Gram-positive pathogens.

Enzyme-mediated mechanisms of resistance were also discovered for natural and semi-synthetic macrolide antibiotics via glycosylation and through a kinase-mediated phosphorylation mechanism. Sequencing of the genome of one of the resistant bacteria identified a macrolide kinase encoding gene and characterization of its product revealed it to be related to a known family of kinases circulating in modern drug resistant pathogens. The implications of this study are significant to our understanding of the prevalence of resistance, even in microbiomes isolated from human use of antibiotics. This supports a growing understanding that antibiotic resistance is natural, ancient, and hard wired in the microbial pangenome.

Related: Alligator Blood Provides Strong Resistance to Bacteria and VirusesBacteria Survive On All Antibiotic DietClay Versus MRSA Superbug

Dangerous Drug-Resistant Strains of TB are a Growing Threat

Drug-resistant strains of TB are out of control

The fight against new, antibiotic-resistant strains of tuberculosis has already been lost in some parts of the world, according to a senior World Health Organisation expert.

Dr Paul Nunn, head of the WHO’s global TB response team, is leading the efforts against multi-drug resistant TB (MDR-TB). Nunn said that, while TB is preventable and curable, a combination of bad management and misdiagnosis was leaving pharmaceutical companies struggling to keep up. Meanwhile, the disease kills millions every year.

“It occurs basically when the health system screws up,” said Nunn. “Treating TB requires a carefully followed regime of medication over six months. In places where health services are fragmented or underfunded, or patients poor and health professionals ill-trained, that treatment can fall short, which can in turn lead to patients developing drug-resistant strains. It’s been estimated that an undiagnosed TB-infected person can infect 10 others a year.

We tend to do a poor job of dealing with systemic effects of poorly functioning systems. Direct present threats get out attention. And we are decent at directing brain power and resources to find solutions. We are not very good at dealing with failures that put us in much worse shape in the long term. For small threats we can wait until it becomes a present threat and then deal with it. There are costs to doing this (economic and personal) but it can be done.

Some problems though become enormously complicated to deal with once they become obvious. Global climate change, for example. And often, even once they are obvious, we won’t act until the costs (economic and in human lives) are very large. It is possible that once we decide to get serious about dealing with some of these issues that the costs (economic and in human lives) will be catastrophic.

The failure to use anti-biotics medicine properly is a very serious threat to become one of these catastrophic societal failures. While tuberculosis failures may be larger in poorer countries, rich countries are failing probably much more critically in the misuse of anti-biotics (I would guess, without having much evidence at my fingertips to back up my opinion. I believe the evidence exists I am just not an expert). These failures have huge costs for all of humanity but we are risking many premature deaths because we systemically fail to deal with issues until the consequences are immediate.

Related: Extensively Drug-resistant Tuberculosis (XDR TB) (2007)What Happens If the Overuse of Antibiotics Leads to Them No Longer Working?Antibiotics Too Often Prescribed for Sinus WoesOveruse of Antibiotics (post from 2005)CDC Urges Increased Effort to Reduce Drug-Resistant Infections (2006)

Potential Antibiotic Alternative to Treat Infection Without Resistance

Researchers at the University of Michigan have found a potential alternative to conventional antibiotics that could fight infection with a reduced risk of antibiotic resistance. Sadly Michigan is another school that is allowing work of those paid for by the citizens of Michigan to be lock away, only due to the wishes of an outdated journal business model instead of supporting open science. The Big Ten seems much more interested in athletic riches than in promoting science. The Big Ten should be ashamed of such anti knowledge behavior and require open science for their schools if they indeed value knowledge.

By using high-throughput screening of a library of small molecules, the team identified a class of compounds that significantly reduced the spread and severity of group A Streptococcus (GAS) bacteria in mice. Their work suggests that the compounds might have therapeutic value in the treatment of strep and similar infections in humans.

“The widespread occurrence of antibiotic resistance among human pathogens is a major public health problem,” said David Ginsburg, a faculty member at LSI, a professor of internal medicine, human genetics, and pediatrics at the U-M Medical School and a Howard Hughes Medical Institute investigator.

Ginsburg led a team that included Scott Larsen, research professor of medicinal chemistry and co-director of the Vahlteich Medicinal Chemistry Core at U-M’s College of Pharmacy, and Hongmin Sun, assistant professor of medicine at the University of Missouri School of Medicine.

Work on this project is continuing at U-M and the University of Missouri, including the preparation of new compounds with improved potency and the filing of patents, Larsen said. Large research schools are also very interested in patents. That is ok, though seems to cloud the pursuit of knowledge too often when too large a focus is on dollars at many schools. But, it seems to put the schools primary focus on dollars; education seems to start to be a minor activity at some of these large schools.

Current antibiotics interfere with critical biological processes in the pathogen to kill it or stop its growth. But at the same time, stronger strains of the harmful bacteria can sometimes resist the treatment and flourish.

An alternate approach is to suppress the virulence of the infection but still allow the bacteria to grow, which means there is no strong selection for strains that are resistant to antibiotics. In a similar experiment at Harvard University, an anti-virulence strategy was successful in protecting mice from cholera.

About 700 million people have symptomatic group A Streptococcus infections around the world each year, and the infection can be fatal. Most doctors prescribe penicillin. The newly identified compounds could work with conventional antibiotics and result in more effective treatment.

Related: full press releaseWhat Happens If the Overuse of Antibiotics Leads to Them No Longer Working?Norway Reduces Infections by Reducing Antibiotic UseNew Family of Antibacterial Agents DiscoveredMany Antibacterial Products May Do More Harm Than GoodAnti-microbial Paint

Microbiologist Develops Mouthwash That Targets Only Harmful Cavity Causing Bacteria

A new mouthwash developed by a microbiologist at the UCLA School of Dentistry is highly successful in targeting the harmful Streptococcus mutans bacteria that is the principal cause tooth decay and cavities.

In a recent clinical study, 12 subjects who rinsed just one time with the experimental mouthwash experienced a nearly complete elimination of the S. mutans bacteria over the entire four-day testing period.

Dental caries, commonly known as tooth decay or cavities, is one of the most common and costly infectious diseases in the United States, affecting more than 50 percent of children and the vast majority of adults aged 18 and older. Americans spend more than $70 billion each year on dental services, with the majority of that amount going toward the treatment of dental caries.

This new mouthwash is the product of nearly a decade of research conducted by Wenyuan Shi, chair of the oral biology section at the UCLA School of Dentistry. Shi developed a new antimicrobial technology called STAMP (specifically targeted anti-microbial peptides) with support from Colgate-Palmolive and from C3-Jian Inc., a company he founded around patent rights he developed at UCLA; the patents were exclusively licensed by UCLA to C3-Jian.

The human body is home to millions of different bacteria, some of which cause diseases such as dental caries but many of which are vital for optimum health. Most common broad-spectrum antibiotics, like conventional mouthwash, indiscriminately kill both benign and harmful pathogenic organisms and only do so for a 12-hour time period.

The overuse of broad-spectrum antibiotics can seriously disrupt the body’s normal ecological balance, rendering humans more susceptible to bacterial, yeast and parasitic infections.

Shi’s Sm STAMP C16G2 investigational drug, tested in the clinical study, acts as a sort of “smart bomb,” eliminating only the harmful bacteria and remaining effective for an extended period.

“With this new antimicrobial technology, we have the prospect of actually wiping out tooth decay in our lifetime,” said Shi, who noted that this work may lay the foundation for developing additional target-specific “smart bomb” antimicrobials to combat other diseases.

Related: full press releaseFalse Teeth For CatsCavity-Fighting LollipopBiologists Identified a New Way in Which Bacteria Hijack Healthy Cells

What Happens If the Overuse of Antibiotics Leads to Them No Longer Working?

Antibiotics have been a miraculous tool to keep up healthy. Like vaccines this full value of this tool is wasted if it is used improperly. Vaccines value is wasted when they are not used enough. Antibiotics lose potency when they are overused. The overuse of anti-biotics on humans is bad (especially the huge amount of just lazy, not scientific use). But the massive overuse in livestock is much worse, it seems to me.

The health system in the USA is broken in a huge way in which it is broken is the failure to address creating systemic behavior that promotes human health and instead just treating illness. It is much better to avoid a situation where we breed super bugs and then try to treat those super bugs that have evolved to be immune to the antibiotics we have to use.

When antibiotics no longer work

While the source of the current salmonella outbreak remains murky, we can reasonably speculate about the genesis of the bug’s drug-resistance: the reportedly endemic overuse of antibiotics by the agricultural industry.

Drugs are given to livestock for multiple reasons. An obvious one is for the treatment of diseases. When livestock are sick, veterinarians administer a significant dosage in hopes of eliminating the animal’s affliction. Another reason is preventative. Animals in close quarters are more susceptible to infection, so farmers will often administer medicine to healthy animals in order to nip anything nasty in the bud. Most controversially, though, members of the agricultural industry use antibiotics for the express purpose of promoting livestock growth.

It’s a well-known, if not entirely intuitive, fact that healthy animals who are fed small, or “sub-therapeutic,” doses of antibiotics will wind up larger than their unmedicated counterparts. In many such cases, these drugs are given to livestock through their feed or water, and without the prescription or oversight of a veterinarian, according to Dr. Gail Hansen, a senior officer at the Pew Campaign on Human Health and Industrial Farming.

An estimated 80 percent of all antibiotics in the U.S. are given to food-producing livestock, according to the FDA. And approximately 83 percent of that medicine is “administered flock- or herd-wide at low levels for non-therapeutic purposes, such as growth promotion and routine disease prevention,” according to a lawsuit filed against the FDA in May. These figures could have very real consequences for public health, because the Catch-22 of this antibiotic abandon is the widespread development of drug-resistant bacteria, colloquially referred to as “super-bugs.”

In 2006, the European Union banned all use of antibiotics on livestock for growth promotion. And the U.S. Senate will consider similar legislation this year. Sen. Dianne Feinstein, D-Calif., reintroduced the “Preservation of Antibiotics for Medical Treatment Act” last month, which would significantly rein in agricultural drug use, and strictly prohibit the application of sub-therapeutic doses of drugs that have benefits for humans.

Still, the agricultural industry disputes data about its use of antibiotics and the rise of super-bugs, and it has aggressively fought efforts to legislate the matter. As a result, it’s hard to tell how far the legislation might proceed.

Related: Antibiotics Too Often Prescribed for Sinus WoesOveruse of Antibiotics (2005)FDA May Make Decision That Will Speed Antibiotic Drug Resistance (2007)

The end of the era of antibiotics

How did this happen? The driving forces are Darwin and human carelessness. Bacteria are constantly evolving, adapting to the changing conditions they face. Antibiotics usually kill bacteria. But sometimes a bacteria will develop a biological defense – particularly if too small a dose is used.

Antibiotics require a prescription in America, but our nation is still very much a part of the problem. Patients routinely demand these drugs, and doctors acquiesce, for respiratory infections and other ailments that will not respond to antibiotics because they are caused by a virus. We use soap with antimicrobial agents when regular soap does equally well. And we allow farmers to feed antibiotics to livestock in horrifying amounts, not to treat illnesses but to make farming more efficient.

The Potential Role of Concentrated Animal Feeding Operations in Infectious Disease Epidemics and Antibiotic Resistance

This working group, which was part of the Conference on Environmental Health Impacts of Concentrated Animal Feeding Operations: Anticipating Hazards—Searching for Solutions, considered the state of the science around these issues and concurred with the World Health Organization call for a phasing-out of the use of antimicrobial growth promotants for livestock and fish production. We also agree that all therapeutic antimicrobial agents should be available only by prescription for human and veterinary use.

Antibiotic Resistance in Livestock: More at Risk Than Steak
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Biologists Identified a New Way in Which Bacteria Hijack Healthy Cells

photo of Zhao-Qing Luo and Yunhao Tan

Associate professor of biological sciences Zhao-Qing Luo, foreground, and graduate student Yunhao Tan identified a new way in which bacteria modify healthy cells during infection. Shown on the computer screen are cells infected with a mutant strain of the bacteria Legionella pneumophila used in their research.

Purdue University biologists identified a new way in which bacteria hijack healthy cells during infection, which could provide a target for new antibiotics. Zhao-Qing Luo, the associate professor of biological sciences who led the study, said the team discovered a new enzyme used by the bacterium Legionella pneumophila – which causes Legionnaires’ disease – to control its host cell in order to take up residence.

“Legionnaires’ disease is a severe form of pneumonia, and this finding could lead to the design of a new therapy that saves lives,” Luo said. “At the same time it also provides great insight into a general mechanism of both bacterial infection and cell signaling events in higher organisms including humans.”

Successful infection by Legionella pneumophila requires the delivery of hundreds of proteins into the host cells that alter various functions to turn the naturally hostile environment into one tailor-made for bacterial replication. These proteins tap into existing communication processes within the cells in which an external signal, such as a hormone, triggers a cascade of slight modifications to proteins that eventually turns on a gene that changes the cell’s behavior, he said.

“Pathogens are successful because they know how information in our cells is relayed and they amplify some signals and block others in order to evade the immune system and keep the cell from defending itself,” Luo said. “Despite our understanding of this, we do not know much about how the proteins delivered by the bacteria accomplish this – how they work. This time we were able to pinpoint an enzyme and see how it disrupted and manipulated a specific signaling pathway in order to create a better environment for itself.”

The signaling pathway involved was only recently identified, and the discovery by Luo and graduate student Yunhao Tan also provides a key insight into its process. The signaling pathway involves a new form of protein modification called AMPylation in order to relay instructions to change cell behavior and has been found to be used by almost all organisms, Luo said.

The bacterium affects the host cell’s functions differently during different phases of the infection process, tapping into signaling pathways to turn on and off certain natural cellular activities. SidD stops the AMPylation process four hours after the start of infection in order to reverse an earlier modification that would be detrimental to the cell if left in place, he said.

Read the full press release.

Related: Using Bacteria to Carry Nanoparticles Into CellsDisrupting Bacterial Communication to Thwart ThemScientists Target Bacteria Where They LiveAre you ready for a world without antibiotics?

Are you ready for a world without antibiotics?

Are you ready for a world without antibiotics?

[Professor Tim Walsh] “This is potentially the end. There are no antibiotics in the pipeline that have activity against NDM 1-producing enterobacteriaceae. We have a bleak window of maybe 10 years, where we are going to have to use the antibiotics we have very wisely, but also grapple with the reality that we have nothing to treat these infections with.”

And this is the optimistic view – based on the assumption that drug companies can and will get moving on discovering new antibiotics to throw at the bacterial enemy. Since the 1990s, when pharma found itself twisting and turning down blind alleys, it has not shown a great deal of enthusiasm for difficult antibiotic research. And besides, because, unlike with heart medicines, people take the drugs for a week rather than life, and because resistance means the drugs become useless after a while, there is just not much money in it.

“The emergence of antibiotic resistance is the most eloquent example of Darwin’s principle of evolution that there ever was,” says Livermore. “It is a war of attrition. It is naive to think we can win.”

I have been writing about the huge risks we are talking with our future for years. The careless misuse of antibiotics is very costly (in human lives, in the future). Bacteria pose great risks to us. We need to take antibiotics to fight serious threats. The misuse of antibiotics by doctors, patients, agri-business… is the problem. And we are all living a much riskier future because far to little is being done to reduce the misuse of antibiotics.

More and more antibiotic treatments are losing effectiveness as bacteria evolve resistance. The evolution is accelerated by misuse. This costs lives today, but is likely to costs many thousands and hundreds of thousands and possible more in the next 50 years.

The NDM-1-producing bacteria were highly resistant to all antibiotics except tigecycline and colistin. In some cases, isolates were resistant to all antibiotics. The emergence of NDM-1 positive bacteria is potentially a serious global public health problem as there are few new anti-Gram-negative antibiotics in development and none that are effective against NDM-1.

Related: Antibiotics Breed Superbugs Faster Than ExpectedAntibiotics Too Often Prescribed for Sinus WoesBacteria Race Ahead of DrugsFDA May Make Decision That Will Speed Antibiotic Drug ResistanceRaised Without AntibioticsWaste Treatment Plants Result in Super BacteriaHow Bleach Kills BacteriaCDC Urges Increased Effort to Reduce Drug-Resistant Infections

Antibiotics, Farming and Superbugs

Antibiotics and farming – how superbugs happen

Provocative new research from Boston University’s medical school and department of biomedical engineering now suggests, though, that multi-drug resistance can be acquired in one pass, through a different mutational process triggered by sublethal doses of antibiotics – the same sort of doses that are given to animals on farms.

In earlier work, the authors found that antibiotics attack bacteria not only in the ways they are designed to (the beta-lactams such as methicillin, for instance, interfere with staph’s ability to make new cell walls as the bug reproduces, causing the daughter cells to burst and die), but also in an unexpected way. They stimulate the production of free radicals, oxygen molecules with an extra electron, that bind to and damage the bacteria’s DNA.

That research used lethal doses of antibiotics, and ascertained that the free-radical production killed the bacteria. In the new research, the team uses sublethal doses, and here’s what they find: The same free-radical production doesn’t kill the bacteria, but it acts as a dramatic stimulus to mutation, triggering production of a wide variety of mutations

Related: A radical source of antibiotic resistance…Overuse of AntibioticsBacteria Race Ahead of DrugsRaised Without Antibiotics

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