10 September 2016

HEALTH - New Molecule Renews Antibiotic Effectiveness

The spectre of drug-resistant infections is a serious concern.

Scientists at Merck, including Terry Roemer, have found a molecule that can once again make antibiotics effective against some drug-resistant infections.

This is great news, because resistant infections are on the rise. Among both people and pets, antibiotic resistance is a growing problem.

But while antibiotic resistance is growing in a variety of bacteria, from UTIs to STIs, it was antibiotic-resistant Staph infections that Roemer and his team focused on.

MRSA, methicillin-resistant Staphylococcus aureus, and MRSE, methicillin-resistant S. epidermidis, are an issue in schools, hospitals, prisons, and anywhere else that people may come into contact with open wounds.

Although the resistant form of the infection is not more virulent, it is much harder to treat. These bacteria have evolved enzymes capable of withstanding the attacks of ß-lactam antibiotics.

ß-lactam antibiotics, including penicillin, methicillin, and the cephalosporins, are among the most commonly prescribed and were the first to be discovered. In fact, it is the prevalence of their use that has resulted in growing antibiotic resistance.

According to a study last year, “The persistent exposure of bacterial strains to a multitude of β-lactams has induced dynamic and continuous production and mutation of β-lactamases in these bacteria.”

These β-lactamases are the enzymes that provide drug resistance.

The fact that MRSA and MRSE have become such an issue in hospitals, schools, and prisons is somewhat ironic.

When Fleming first discovered penicillin, it was while studying Staphylococcus colonies. It was the Staph bacterium that opened the door to the antibiotic era, and the Staph bacterium seems determined to close that same door.

Thankfully researchers are working hard to prevent that, and the development of tarocins – the molecules which, when combined with ß-lactam antibiotics, inhibit the enzymes protecting the bacteria – is a step towards once again having reliable and effective treatments for Staph infections.

The development of tarocin A took an unusual path.

Rather than trying to develop a new drug that would be effective on its own, the team focused exclusively on developing a nonbioactive molecule. This sped up the process of clinical trials and cleared the regulatory path.

Tarocin A becomes active only when combined with existing ß-lactam antibiotics, and once it is combined it showed a restored susceptibility of 82% of MRSA samples and 77% of MRSE samples.

Trials in mice show that treatment with the combined ß-lactam and tarocin A had no adverse effects, and significantly increased effectivity. Treatment with only one or the other did not clear the infection.

Although the rates of hospital-acquired MRSA infections have been falling, it is difficult to determine how many people are affected by drug-resistant infections.

Deaths caused by drug-resistant infections are often not properly documented, due to a combination of lack of experience and the stigma associated with hospital-acquired infections. When these infections become treatable again, hospital patients will be safer.


By Tiffany Sostar
Tiffany is a writer, editor, academic, and animal lover who came late to her appreciation of pets. At 18, a rescue pup named Tasha saved her from a depression and she hasn't looked back. She has worked as the canine behaviour program coordinator for the Calgary Humane Society, and was a dog trainer specializing in working with fearful and reactive dogs for many years. She doesn't have any pets right now, but makes up for it by giving her petsitting clients (and any dogs she comes across on her frequent coffee shop adventures) extra snuggles.

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