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To beat superbug bacteria, look to frog skin

U. MELBOURNE (AUS) — In search of ways to fight antibiotic-resistant bacteria, scientists are looking to synthetic anti-microbial skin secretions from frogs.

Two species, Australian Green-Eyed and Growling Grass frogs, were selected because peptides secreted from their skin form a defense to a broad spectrum of bacteria including Staphylococcus. Commonly known as superbugs, antibiotic-resistant bacteria can pose significant risks to human health.

The research is under way at the Australian Nuclear Science and Technology Organisation (ANSTO), where scientists are using neutrons from Australia’s only nuclear reactor.

Professor Frances Separovic from the School of Chemistry and Bio21 Institute at the University of Melbourne is leading the research with the expertise of ANSTO’s postdoctoral research fellow Anton Le Brun, and Professor Michael James.

“With the increase in antibiotic resistance, peptides (small proteins) that destroy cell membranes are being considered as therapeutics. However, there is a need for peptides that preferentially destroy bacterial membranes,” says Separovic.

“We have characterized several peptides from the skin glands of Australian tree frogs. These peptides are host defense compounds, which have strong antibacterial activity. By understanding their 3-D structure and mechanism of action at the molecular level, we may be able to increase their antibiotic potency and specificity.”

Le Brun explains there are three questions that need to be answered when studying the active ingredients of the secretions or antimicrobial peptides:

“Firstly, we’re using facilities at the OPAL reactor to analyze how and why the peptides from the frog skin secretions work, and how they are efficient at killing bacterial cells,” says Le Brun.

“And, of course, given that we don’t want them to attack healthy human (or frog) cells, we also need to establish whether and how these antimicrobial peptides are selective for bacterial cells.

“The OPAL reactor and neutron reflectometer will help us provide further information to answer those questions, and research possible alternative treatments or cures for superbugs.

“With neutron reflectivity, we can individually detect both the peptide that attacks the cell membrane of bacteria, and the membrane itself—providing a better picture of the process.

“It’s this component by component analysis that will help us understand how two different types of frog peptides from two different types of frogs deliver the same outcome: dead bacteria.”

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