Nav: Home

Biophysicists discover how small populations of bacteria survive treatment

March 13, 2018

Small populations of pathogenic bacteria may be harder to kill off than larger populations because they respond differently to antibiotics, a new study by Emory University finds.

The journal eLife published the research, showing that a population of bacteria containing 100 cells or less responds to antibiotics randomly -- not homogeneously like a larger population.

"We've shown that there may be nothing special about bacterial cells that aren't killed by drug therapy -- they survive by random chance," says lead author Minsu Kim, an assistant professor in the Department of Physics and a member of Emory's Antibiotic Resistance Center.

"This randomness is a double-edged sword," Kim adds. "On the surface, it makes it more difficult to predict a treatment outcome. But we found a way to manipulate this inherent randomness in a way that clears a small population of bacteria with 100 percent probability. By tuning the growth and death rate of bacteria cells, you can clear small populations of even antibiotic-resistant bacteria using low antibiotic concentrations."

The researchers developed a treatment model using a cocktail of two different classes of antibiotic drugs. They first demonstrated the effectiveness of the model in laboratory experiments on a small population of E. coli bacteria without antibiotic-drug resistance. In later experiments, they found that the model also worked on a small population of clinically-isolated antibiotic-resistant E. coli.

"We hope that our model can help in the development of more sophisticated antibiotic drug protocols -- making them more effective at lower doses for some infections," Kim says. "It's important because if you treat a bacterial infection and fail to kill it entirely, that can contribute to antibiotic resistance."

Antibiotic resistance is projected to lead to 300 million premature deaths annually and a global healthcare burden of $100 trillion by 2050, according to the 2014 Review on Antimicrobial Resistance. The epidemic is partly driven by the inability to reliably eradicate infections of antibiotic-susceptible bacteria.

For decades, it was thought that simply reducing the population size of the bacteria to a few hundred cells would be sufficient because the immune system of an infected person can clear out the remaining bacteria.

"More recently, it became clear that small populations of bacteria really matter in the course of an infection," Kim says. "The infectious dose -- the number of bacterial cells needed to initiate an infection -- turned out to be a few or tens of cells for some species of bacteria and, for others, as low as one cell."

It was not well understood, however, why treatment of bacteria with antibiotics sometimes worked and sometimes failed. Contributing factors may include variations in the immune responses of infected people and possible mutations of bacterial cells to become more virulent.

Kim suspected that something more fundamental was a factor. Research has shown unexpected treatment failure for antibiotic-susceptible infections even in a simple organism like the C. elegans worm, a common model for the study of bacterial virulence.

By focusing on small bacteria populations, the Emory team discovered how the dynamics were different from large ones. Antibiotics induce the concentrations of bacterial cells to fluctuate. When the growth rate topped the death rate by random chance, clearance of the bacteria failed.

The researchers used this knowledge to develop a low-dose cocktail drug therapy of two different kinds of antibiotics. They combined a bactericide (which kills bacteria) and a bacteriostat (which slows the growth of bacteria) to manipulate the random fluctuation in the number of cells and boost the probability of the cell death rate topping the growth rate.

Not all antibiotics fit the model and more research is needed to refine the method for applications in a clinical setting.

"We showed that the successful treatment of a bacterial infection with antibiotics is even more complicated than we thought," Kim says. "We hope this knowledge leads to new strategies to fight against infections caused by antibiotic-resistant bacteria."

Emory Health Sciences

Related Bacteria Articles:

Conducting shell for bacteria
Under anaerobic conditions, certain bacteria can produce electricity. This behavior can be exploited in microbial fuel cells, with a special focus on wastewater treatment schemes.
Controlling bacteria's necessary evil
Until now, scientists have only had a murky understanding of how these relationships arise.
Bacteria take a deadly risk to survive
Bacteria need mutations -- changes in their DNA code -- to survive under difficult circumstances.
How bacteria hunt other bacteria
A bacterial species that hunts other bacteria has attracted interest as a potential antibiotic, but exactly how this predator tracks down its prey has not been clear.
Chlamydia: How bacteria take over control
To survive in human cells, chlamydiae have a lot of tricks in store.
Stress may protect -- at least in bacteria
Antibiotics harm bacteria and stress them. Trimethoprim, an antibiotic, inhibits the growth of the bacterium Escherichia coli and induces a stress response.
'Pulling' bacteria out of blood
Magnets instead of antibiotics could provide a possible new treatment method for blood infection.
New findings detail how beneficial bacteria in the nose suppress pathogenic bacteria
Staphylococcus aureus is a common colonizer of the human body.
Understanding your bacteria
New insight into bacterial cell division could lead to advancements in the fight against harmful bacteria.
Bacteria are individualists
Cells respond differently to lack of nutrients.

Related Bacteria Reading:

From Bacteria to Bach and Back: The Evolution of Minds
by Daniel C. Dennett (Author)

“[The] best scientific-philosophical approach to understanding how consciousness evolved.… A wonderful book that will shape and drive thinking for years to come.”―Shane O’Mara, Times Higher Education

How did we come to have minds? For centuries, poets, philosophers, psychologists, and physicists have wondered how the human mind developed its unrivaled abilities. Disciples of Darwin have explained how natural selection produced plants, but what about the human mind?

In From Bacteria to Bach and Back, Daniel C. Dennett builds on recent... View Details

Bacteria: Staph, Strep, Clostridium, and Other Bacteria (Class of Their Own (Paperback))
by Judy Wearing (Author)

Bacteria are microscopic organisms with a cell structure that is very different from that of the other kingdoms. Traditionally classified according to their shape, scientists now use DNA studies to refine the groupings of bacteria. This book examines bacteria that are found in virtually every environmentincluding those that are characterized by extreme heat, cold, and depthand, of course, bacteria that are found inside our bodies. Intriguing information highlights the key role that bacteria play in shaping the ecology of our planet, how some bacteria make their own food while others feed on... View Details

The Bacteria Book: The Big World of Really Tiny Microbes
by Steve Mould (Author)

In this funny and fact-packed introductory science book, kids will meet the bacteria, viruses, and other germs and microbes that are all around, but too small for us to see.

What do a squid that glows, fungus that grows, and tiny creatures in the soil under your toes all have in common? Find out in this dynamic and engaging book all about bacteria, viruses, and other germs and microbes. The Bacteria Book walks the line between "ew, gross!" and "oh, cool!," exploring why we need bacteria and introducing readers to its microbial mates--viruses, fungi, algae, archaea, and... View Details

Bacteria: A Very Short Introduction (Very Short Introductions)
by Sebastian G.B. Amyes (Author)

Bacteria form a fundamental branch of life. They are the oldest forms of life and the most prolific of all living organisms, inhabiting every part of the Earth's surface, its ocean depths, and even such inhospitable places as boiling hot springs. In this Very Short Introduction, bacteriologist Sebastian Amyes explores the nature of bacteria, their origin and evolution, bacteria in the environment, and bacteria and disease. Amyes discusses some of the major infections caused by bacteria-bacteria causes pneumonia, diphtheria, cholera, and many other diseases-and shows how these... View Details

A Field Guide to Bacteria (Comstock Book)
by Betsey Dexter Dyer (Author)

"Although most people are aware that bacteria are all around us, few would guess that they produce such distinctive and accessible signs. Whether you're walking on the beach, visiting a zoo or aquarium, buying groceries, looking for fossils, drinking beer, traipsing through a swamp, or cleaning scum from beneath a dripping outdoor faucet, you're surrounded by bacterial field marks. You don't need a laboratory or fancy equipment to find out what kind of bacteria are there―this guide will tell you how."―from the IntroductionBacteria are an integral aspect of every habitat in which they... View Details

Are All Bacteria Dangerous? Biology Book for Kids | Children's Biology Books
by Baby Professor (Author)

If you're child is into science, or you would like him/her to be, then this biology book is a must-have! Bacteria is always all around us but that doesn't mean we should be perpetually afraid of them. Lack of knowledge on the subject will make you fear too much. That is why it is important to encourage your child to pick up the habit of reading. View Details

The Surprising World of Bacteria with Max Axiom, Super Scientist (Graphic Science)
by Agnieszka Biskup (Author), Anne Timmons (Author), Matt Webb (Author), Krista Ward (Author)

"In graphic novel format, follows Max Axiom as he explores the world of bacteria"--Provided by publisher. View Details

Premed Kids: Microbiology - Bacteria & Viruses
by April Chloe Terrazas (Author)

From the author/illustrator of the SUPER SCIENCE SERIES comes a new exploratory science children's series, Premed Kids! Premed Kids is an intro to topics covered on the MCAT, the medical school entry test! Start learning early so you can become a doctor (which is just another awesome form of a scientist!) This quick read is stuffed with new microbial vocabulary plus April's signature "sound it out" phonics guides for early readers. Enjoy 18 pages packed with delightful illustrations and fun facts. Ever wonder how the flu virus gets into your cells? Want to know what a bacterium looks like? By... View Details

Molecular Genetics of Bacteria, 4th Edition
by Larry Snyder (Author), Joseph E. Peters (Author), Tina M. Henkin (Author), Wendy Champness (Author)

The classic comprehensive and authoritative textbook on bacterial molecular genetics.

Features completely revised and updated material and new chapters, incorporating the most recent advances in the field since publication of the third edition in 2007. Provides thought questions, problems, and suggested reading lists for each chapter that test student comprehension and encourage further research. Provides descriptive background information, detailed experimental methods, examples of genetic analyses, and advanced material relevant to current applications of molecular genetics. Serves... View Details

I Contain Multitudes: The Microbes Within Us and a Grander View of Life
by Ed Yong (Author)

Joining the ranks of popular science classics like The Botany of Desire and The Selfish Gene, a groundbreaking, wondrously informative, and vastly entertaining examination of the most significant revolution in biology since Darwin—a “microbe’s-eye view” of the world that reveals a marvelous, radically reconceived picture of life on earth.

Every animal, whether human, squid, or wasp, is home to millions of bacteria and other microbes. Ed Yong, whose humor is as evident as his erudition, prompts us to look at ourselves and our animal companions in a new... View Details

Best Science Podcasts 2018

We have hand picked the best science podcasts for 2018. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

The Consequences Of Racism
What does it mean to be judged before you walk through the door? What are the consequences? This week, TED speakers delve into the ways racism impacts our lives, from education, to health, to safety. Guests include poet and writer Clint Smith, writer and activist Miriam Zoila Pérez, educator Dena Simmons, and former prosecutor Adam Foss.
Now Playing: Science for the People

#466 Wildfire
This week we're talking about fire: in particular, wildfires. How they spread and how we manage them, but also the deeper history of wildfires on our planet and how they've been shaping our world for a long, long time. We speak with Andrew Scott, Emeritus Professor of Geology at Royal Holloway, University of London, about his book "Burning Planet: The Story of Fire Through Time", learning about wildfire on our planet now and in deep history. And we catch up with Caroline Weinberg, interm executive director of the March for Science organization, about this year's march on April 14.