A novel antibiotic treatment inspired by our immune system

Researchers from the National University of Ireland Galway have developed a new antibacterial treatment, effective against drug-resistant bacteria, which takes inspiration from the human immune system.

This treatment, called the ‘iodo-thiocyanate complex’, or ITC for short, also showed a low propensity to lead to the development of resistant bacterial strains.

The paper was published on May 2 in the journal Frontiers in Microbiology.

Work on the treatment began in response to the increasing emergence of antibiotic-resistant bacteria. As more and more bacteria become immune to antibiotics, and the number of drugs we can rely on dwindle away, our ability to fight back against life-threatening infections is diminishing significantly – meaning it’s more important than ever to find new ways to deal with these organisms.

The complex is a combination of three ingredients – iodide, thiocyanate and hydrogen peroxide. Which react together to generate oxidised molecules with antimicrobial properties. These molecules can kill bacteria by damaging important cellular structures and components, leading to cell death.

Our immune system features a similar mechanism, which works through peroxidase enzymes. In the presence of hydrogen peroxide, these enzymes allow the production of oxidised molecules and can be found in a number of bodily secretions, such as milk, tears and gastrointestinal fluid.

So why haven’t peroxidase enzymes been incorporated into an antimicrobial treatment? The problem is that purifying the enzymes can be extremely expensive, and actually producing enough to be used as an antimicrobial wouldn’t be feasible.

However, while ITC works under the same principal, it doesn’t need peroxidase enzymes to work, meaning a similar effect could generated with much less cost.

The researchers tested the antibiotic effects of ITC on a range of bacterial strains, both planktonic (in free-floating cell suspensions) and in biofilms. These biofilms, a layer of bacteria which can coat a wide variety of surfaces, are particularly dangerous as they’re capable of contaminating medical equipment, such as catheters, or infecting wounds – which can lead to life threatening infections. What’s more, bacteria in a biofilm formation have been associated with a greater tendency to develop antibiotic resistance.

It was found that ITC could kill all bacteria tested against, including methicillin resistant Staphylococcus aureus (MRSA), both when the bacteria were planktonic and in biofilms. In some cases, the complex was able to kill the bacteria within 30 seconds.

The treatment was effective against a range of planktonic and biofilm bacterial formations. Image credit: Lilit Tonoyan.

They also discovered that the effectiveness of ITC to kill the bacteria didn’t diminish after repeated applications, suggesting that the complex doesn’t lead to the emergence of resistant bacteria. This is probably because of the fact that the complex contains two substrates (iodide and thiocyanate) which, when oxidised, produce a ‘cocktail’ of different antimicrobial molecules with different targets. A multitude of targets means that it’s much less likely that resistant bacterial strains will emerge.

The research team hope that the treatment could be used to disinfect surfaces and help treat infected wounds. However, the next step would be to make sure that the complex is safe to use in people.

“We will need to assess the safety and suitability of the complexes for use in, or on, humans,” said Professor Vincent O’Flaherty, one of the study’s authors. “We will also need to develop delivery systems to deploy the treatment in a variety of settings that are currently affected by antibiotic-resistant bacteria.”

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