Evolution Update

Evolution Update

A New Class of Antibiotics Less Susceptible to Evolutionary-Driven Resistance Development

Brandon Kieft October 30, 2016

Pathogenic bacteria are evolving resistance to our antibiotics at an alarming rate, however, scientists have recently discovered a molecule that may help combat these microscopic killers.

athogenic bacteria that can infect our bodies and evade our immune systems to cause illness, suffering, or death have been one of the major stories in human history.

That is, until a man named Alexander Fleming (accidentally) changed the game forever with his discovery of the first known antibiotic benzylpenicillin. Ever since, humanity has basked in the glory of our golden touch and we are no longer concerned with pathogens from our environment infecting our warm, wet bodies; the end.

Unfortunately, no, because: evolution. Pathogenic bacteria have been concurrently evolving molecular weapons to fight one another along with resistance to these weapons for millions (and maybe billions) of years in what biologists typically call a molecular arms race.

As our use of antibiotics increased tremendously since their discovery, it created an intense natural selection for human-dwelling pathogenic bacterial species who could survive the antibiotic onslaught. This elevated scope of exposure unwittingly caused us to produce organisms that have been deemed “superbugs”.

These superbugs cannot easily be killed by our immune system and cannot be killed by any (or most) known drugs. Therefore, scientists have been hard at work attempting to create molecules or other means by which to defend ourselves against these dangerous pathogens.

A recent and exciting discovery on this front is from a group of Australian researchers and was published in the journal Nature Microbiology last month.

The authors described a molecule they created called a SNAPP (structurally nanoengineered antimicrobial peptide polymer), which is formed from chains of amino acids arranged around a small, center core into a 16- or 32-point star shape.

When many of these molecules are put into a solution, they will aggregate together into groups about one eighth the size of a bacterial cell. Once it encounters a cell, the SNAPP “globule”, which is positively charged, will stick to the negatively charged outer membrane of the bacterium and pierce its way into the negatively charged cytoplasm (innards) of the cell by electrostatic (opposites attract) and physical (pointy, star shape) interactions.

In the report, SNAPPs were shown to be very effective in killing drug resistant bacteria in test tubes and in infected mouse models, where it saved the lives of mice compared with those given no treatment or the current best treatment and resulted in minimal damage to mammalian cells.

Better yet, the researchers exposed bacteria to a sub-lethal dose of their SNAPPs for over 600 generations and found no evidence for the development of antibiotic resistance.

This a critically important discovery towards sustainable pathogen clearance and hopefully someday will help save the lives of those infected with these superbugs.

However, is the risk of bacteria evolving antibiotic resistance to SNAPPs inconceivable? Could a pathogenic population overcome the seemingly impossible task of protecting itself against a physically and electrostatically disrupting molecule? The answers are yet unknown, but this class of antibiotics certainly seems to be promising in the human quest for increasing quality of life.

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