Scientists Battle Bacteria with Silver and Mucus

As more bacteria become resistant to antibiotics, scientists search for new as well as old ways to keep infections in check.

Antibiotics changed how doctors treat infections,
allowing people to survive infections and minor injuries that at one time would have killed them.
But ever since antibiotics were introduced in the early 1940s, bacteria have been evolving resistance to these life-saving medicines.
Antibiotic resistance occurs naturally over time, but misuse of antibiotics has speeded up the process.
As the number of infections that are difficult to treat with antibiotics increases, the health of everyone around the world becomes more at risk.
Scientists are trying to stay one step ahead of bacteria by developing new ways of preventing antibiotic resistance or keeping harmful bacteria in check.

 Two recent studies presented in April at the Experimental Biology 2017 meeting in Chicago provide a glimpse at the attempts to regain ground lost to bacteria over the past decades.
One study turned to an ancient method for preventing infections — updated for the 21st century.
The other tried to replicate a trick the body uses for maintaining a healthy balance of bacteria living in the body.

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Silver is an ancient antibiotic

Since ancient times, silver has been used to keep bacteria from contaminating food and water.
Early records even show that doctors used silver to prevent surgical infections or to help wounds heal faster.
More recently, compounds containing fine particles of silver were a major defense against bacterial infections until antibiotics became commonplace.
Now, researchers at the University of Calgary are using modern laboratory techniques to study how silver can kill bacteria — and why it doesn’t always work.
One tool being used is the genome editing technique CRISPR-Cas9, which allows researchers to find and delete specific segments of bacterial DNA.
By doing this, they can identify genes that give bacteria the ability to resist silver’s antibacterial properties or make them vulnerable.

 Right now, researchers are focused on using CRISPR-Cas9 to understand silver toxicity and resistance in the bacteria E. coli.

Many research groups, including ours, have demonstrated that numerous silver compounds are efficacious for killing many bacterial strains

Joe Lemire, University of Calgary

This may eventually lead to better ways of treating infections.
“Many research groups, including ours, have demonstrated that numerous silver compounds are efficacious for killing many bacterial strains, including antibiotic-resistant ones,” Joe Lemire, a postdoctoral fellow at the University of Calgary, and study author, told Healthline.
In a 2013 study, another group of researchers used silver and antibiotics together to enhance the ability of the antibiotic to kill certain species of bacteria.
These researchers suggested that silver works by increasing reactive oxygen species — free radicals — and making the bacterial wall more permeable. That allows antibiotics to enter the cell.

 Understanding how bacteria become resistant may also enable policymakers to develop better guidelines for using silver to prevent or treat infections.
This is one goal of the World Health Organization (WHO), which outlined strategies in 2015 for preventing antimicrobial resistance in antibiotics.
“If we aim to protect the utility of antimicrobials, including silver, we should endeavor to use them only when needed,” said Lemire. “Policy and guidelines on antimicrobial use are excellent ways to protect these public goods.”

This will be challenging given that silver nanoparticles are now used in many medical items such as catheters and wound dressing as well as consumer goods like toothbrushes, toothpaste, bedding, and clothing.
Earlier this year, researchers at the University of Technology Sydney investigated more than 140 commercially available medical devices and other products.
They wrote in the journal ACS Nano that prolonged exposure to these products may create conditions for bacteria to become resistant to the antimicrobial effects of silver.

Synthetic mucus tames bacteria

Another approach to killing bacteria has also been around for a long time, but it’s one that is a lot closer to home — the use of mucus in the body.
Researchers from the Massachusetts Institute of Technology (MIT) are trying to create synthetic mucus in the lab that can mimic the antimicrobial ability of natural mucus.
“We want to use these engineered polymers to control problematic pathogens inside and outside of the body and to stop the growing threat of antibiotic resistant microbes,” Katharina Ribbeck, PhD, a professor of tissue engineering at MIT, said in a press release.
You may be most familiar with mucus in the nose, but this particular substance also forms a protective coat on the inner surface of the digestive tract, lungs, mouth, female reproductive tract, and on the surface of the eyes.

Through their research, Ribbeck and her colleagues have discovered that mucus helps keep harmful bacteria on those surfaces from growing out of control.

The mucus does not kill the microbes. Instead, it tames them.

Katharina Ribbeck, Massachusetts Institute of Technology

“The mucus does not kill the microbes,” said Ribbeck. “Instead, it tames them.”
They found that mucins — sugar-coated molecules that make up the mucus gel — keep bacteria in check by preventing biofilms from forming. Biofilms are communities of bacteria that stick to each other and often to a surface.
The researchers tested this on two types of Streptococcus bacteria that are commonly found in the mouth — one that causes cavities and a second “healthy” bacteria.

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When grown in the absence of saliva or mucin, harmful bacteria quickly outgrew the healthy species. But when grown in the presence of MUC5B — a mucin found in saliva — the two bacteria grew in a more balanced way.
“We conclude from these findings that MUC5B may help prevent diseases such as dental caries [cavities] by reducing the potential that a single harmful species will dominate,” said Ribbeck.
The researchers plan on continuing to investigate how mucins help maintain a diverse balance of microbes on other mucosal surfaces in the body.