Scientists discover a shocking ‘disappearing act’ that bacteria use to hide from antibiotics


Bacteria are microscopic but what they lack in size, they more than make up for in ingenuity. And as one of Earth’s earliest life forms (think 2.5 billion years), they have many tricks up their invisible sleeves. But scientists have recently decoded one particularly clever trick these tiny pranksters use to avoid being detected by antibiotics.

 

E. coli bacteria
One of the troublemakers: Escherichia coli, commonly known as E. coli. Photo by Visual Hunt license CC0 1.0 Public Domain

Researchers at Newcastle University in the U.K. studied samples from elderly patients with recurring urinary tract infections (UTI) by calling in some heavy-duty support: state-of-the-art techniques that helped them to identify one bacteria that commonly makes its cell wall disappear, the University announced in a statement.

 

And this is the first study to show that bacteria within the human body can change shape, hiding the cell wall inside themselves. By concealing the cell wall, antibiotics no longer have a target to work with, providing a nifty form of resistance, The Independent reports.

 

Bacteria in a petri dish
Another view of E. coli bacteria, which are often implicated in urinary tract infections. Photo by azartaz license CC 2.0 via Wikimedia Commons

 

That ability to survive without a cell wall is known formally as “L-form switching,” and it shows that when antibiotics are present — as was the case with the UTI patients who received cell-wall targeting antibiotics — the bacteria are able to change shape.

 

“Imagine that the wall is like the bacteria is wearing a high-vis jacket,” said the study’s lead author, Dr. Katarzyna Mickiewicz. “This gives them a regular shape — for example, a rod or a sphere, making them strong and protecting them but also makes them highly visible — particularly to the human immune system and antibiotics like penicillin.”

This definitely puts a new spin on the phrase “disappearing act.”

 

“What we have seen is that in the presence of antibiotics, the bacteria are able to change from a highly walled-regular form to a completely random, cell wall-deficient L-form state — in effect shedding the yellow jacket and hiding it inside themselves.”

In a way, this is almost like a magic trick on a microscopic level. It’s not long before the body’s immune system and the antibiotics that protect it are led astray.

 

“In this form, the body can’t easily recognize the bacteria so doesn’t attack them, and neither do antibiotics.”

According to the World Health Organization, antibiotic resistance poses a major threat to global health as well as food security and development.

 

In an earlier study, the research team showed that the immune system can also induce L-form switching — to a lesser effect, but overall antibiotic treatment produces a more profound effect. And the current research shows that L-forms of at least some bacterial species associated with some UTIs, including E. coli, Enterococcus, Enterobacter and Staphylococcus in all but one of the 30 patients involved in the study.

 

And even though the L-form in these particular species is flimsy and weak, some manage to survive, hiding inside the body. Sneaky little critters aren’t they?

 

Researchers also isolated L-form bacteria from a patient being treated for a UTI and, in a video, showed the cell walls reforming once the antibiotics were gone. The process took about five hours. The next step was to demonstrate that L-form switching was possible inside the whole of a living organism — not just in the artificial environs of a lab. The team did this with the aid of microscopy and a transparent zebrafish model (which you can see below.)

 

Bacteria are evident in this photo
This photo by Newcastle University shows fluorescently labeled neutrophils (immune cells inside the zebrafish) indicating the presence of bacteria. Photo courtesy of Newcastle University

 

“In a healthy patient, this would probably mean that the L-form bacteria left would be destroyed by the patient’s immune system,” Mickiewicz explained. “But in a weakened or elderly patient, like in our samples, the L-form bacteria can survive. They can reform their cell wall and the patient is faced yet again with another infection.”

 

Mickiewicz and her team may have found one missing piece of the puzzle surrounding resistant bacterial strains and this in itself may provide physicians with more effective treatments.

 

“And this may well be one of the main reasons why we see people with recurring UTIs,” she noted. “For doctors, this may mean considering a combination treatment — so an antibiotic that attacks the cell wall then a different type for any hidden L-form bacteria, so that one targets the RNA or DNA inside, or even the surrounding membrane.”

For those of us beset with problematic immune systems, this sounds like good news. And maybe this will give bacteria like E. coli a run for their collective money. Humans, like all living beings, are engaged in an evolutionary arms race, and who knows where this will go from here?

 

The team’s findings have been published in the journal Nature Communications.

 

Here’s the video that shows the bacteria in action.

 


Photo courtesy of NIAID license CC 2.0 via Flickr


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