Star-shaped polymers to kill superbugs

Researchers have developed tiny, star-shaped molecules that can apparently kill superbugs — bacteria that are no longer affected by current antibiotics. The star-shaped structures are short chains of proteins called ‘peptide polymers’ and were created by a team from the University of Melbourne and the University of South Australia.

“These new synthetic antibiotics (SNAPPs) are modelled on naturally occurring antimicrobial peptides, but have a distinct dendritic structure and simplified amino acid composition,” said team member Dr Anton Blencowe, from the University of South Australia.

A study published in the journal Nature Microbiology found that the star-shaped peptide polymer is extremely effective at killing Gram-negative bacteria — a major class of bacteria known to be highly prone to antibiotic resistance. It is also effective in superbugs when tested in animal models, with superbugs showing no signs of resistance against these peptide polymers.

“In preliminary trials, SNAPPs displayed excellent biocompatibility and activity within a living organism or natural setting and multidrug-resistant bacteria treatments were successful, while treatment with other antibiotics used for severe bacterial infections failed,” said Dr Blencowe.

Unlike most antibiotics, which kill with a single pathway, the star-shaped peptide polymers can kill bacteria with multiple pathways — one of which includes ripping apart the bacteria cell wall. The team believes this explains the polymer’s superior performance, with Dr Blencowe explaining that this method “helps to prevent the development of antibacterial resistance”.

“Even after 600 generations of growth over 24 days in the presence of sub-lethal concentrations of SNAPPs, multidrug-resistant bacteria capable of mutating displayed no resistance to lethal doses,” he said. Furthermore, the polymer’s toxicity is so low that the dosage rate would need to be increased by a factor of greater than 100 to have a negative effect on the body.

While more research is needed, the team believe their discovery holds promise for a new treatment method against antibiotic-resistant bacteria. Dr Blencowe said, “The excellent antimicrobial activity of SNAPPs, combined with good biocompatibility and relatively simple manufacture, make this new class of antimicrobial agents a significant advance in the fight against multidrug-resistant bacteria.”

Image caption: A bacterial cell before and after treatment with the star-shaped polymers.