New antibiotic unearthed from the dirt


"Our idea is, there's this reservoir of antibiotics out in the environment we haven't accessed yet". That's where numerous most widely used antibiotics in medicine come from. Because of this, scientists the world over are looking for new antibiotics.

Scientists said they used a high-throughput sequencing-based screening method that bypasses the need to grow microorganisms first because the vast majority of bacterial species cannot be cultured in the laboratory, and thus can be used to "quickly mine new drug candidates from diverse environmental sources". Another antibiotic daptomycin kills bactarial cells walls by breaking them down.

But how did the researchers sift through almost 2,000 soil samples to zero in on these microscopic antibiotic-makers?

In a study published yesterday in Nature Microbiology, Brady and his colleagues report on the discovery of a class of antibiotics that he says are one of the best examples to come from this platform.

The new class of antibiotics malacidins, kills several superbugs - including the dreaded methicillin-resistant Staphylococcus aureus (MRSA) - without engendering resistance. Daptomycin is the most well-known of these drugs. Culture-independent discovery of the malacidins as calcium-dependent antibiotics with activity against multidrug-resistant Gram-positive pathogens. The team of researchers used Malacidin against MRS for consecutive 20 days to see if the bacteria could mutate and develop any resistance to the antibiotic.

According to The Washington Post, the breakthrough was made by a process of cloning significant quantities of DNA from hundreds of soil samples obtained from across the USA, sent in by a team of eager citizens scientists. They then cloned those genes and looked for the clones with the calcium-dependent variant, or marker, gene. Because all the genes needed to make a molecule in bacteria cluster together, identifying the marker gene enabled them to find all the other genes in the gene cluster. Instead of growing new antibiotics in the lab, he wants to find them out in the field - in this case, quite literally.

As antibiotic resistance becomes more common, scientists are racing to discover new drugs that can fight these risky bacterial infections. 'This might be a way of reducing resistance'.

Speaking with BBC Science about the discovery, lead researcher Dr Sean Brady said: "It is impossible to say when, or even if, an early stage antibiotic discovery like the malacidins will proceed to the clinic". At present the team is working towards making synthetic versions of Malacidin or finding its analogs in nature for mass production.