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Scientists discover new antibiotic family in soil

14 February 2018

"The malacidins are active against multidrug-resistant pathogens, sterilize methicillin-resistant Staphylococcus aureus skin infections in an animal wound model and did not select for resistance under our laboratory conditions", researchers said in a report published in the journal Nature Microbiology.

Although calcium-dependent, the structure and mode of action of malacidins are unlike other antibiotics in this family. While it was taken from daptomycin, is appears to work differently. But scientists have reason to believe it will hold up at least as well.

Using DNA sequenced from more than a thousand soil samples, the scientists searched for gene variants that might be related to calcium dependence and found a much larger family of genes than they had envisioned.

Not bad for a compound that's been hiding in soil for eons.

The team is now working to improve the effectiveness of their treatment so it could be used in people.

Finding new antibiotics is key to staying one step ahead of bacteria threats, but only one new class - teixobactin - has been discovered in the last 33 years.

The identification of this new antibiotic is similar to that of penicillin, the world's first antibiotic drug first discovered in mold bacteria by Scottish scientist Alexander Fleming in 1928.

As a result, numerous workhorses of the world of antibiotics - members of the penicillin, cephalosporin and carbapenem classes - are losing their ability to fight a lengthening list of bacterial diseases.

Unless new antibacterial agents are discovered and turned into medicines, mortality rates due to untreatable infections are predicted to rise more than tenfold by 2050. In that respect, the Rockefeller University team's approach of turning to nature for leads is fairly unique.

It is also a promising sign that this new class follows closely after the 2015 discovery of teixobactin.

Sean Brady, a chemical biologist at Rockefeller University in NY, and a team of colleagues, sequenced bacterial DNA they had taken from 2,000 soil samples collected across the United States.

In order to hasten the process of culturing soil bacteria in a lab, the researchers used high-speed computer processing to "screen" their soil sampled for this calcium use. The team next cloned the relevant genes and rearranged them to insert into a host organism Streptomyces.

Study author Professor Sean Brady from The Rockefeller University in NY, said: 'Topical administration was successful in sterilising MRSA-infected wounds in a rat model. "It is a long, arduous road from the initial discovery of an antibiotic to a clinically used entity". They hypothesized that the genes responsible for this "calcium-dependent motif" might be found in other compounds. And even when they can be grown in the lab, Brady said in an interview, "We don't turn on most of their capacity to make chemistry".

This is not the first time that scientists have discovered antibiotics from the soil, but it has proven hard for researchers to identify a a bacterial species that could become a drug, as the scientists did here.

Scientists discover new antibiotic family in soil