For years, scientists around the world have dug into sand hills and mud pits to discover new antibiotics. But maybe they need look no further than their own pile of poop.
The microbes that roam our guts could be gold mines for new antibiotics, researchers report this week Nature Chemical Biology. As proof of gut bacteria’s potential, the authors unearthed a new bacteria-killing drug that could reverse resistance in pathogens and help kill methicillin-resistant ones. Staphylococcus aureus (MRSA) bacteria. In mice with deadly MRSA infections, the drug helped cure 100 percent of the infections.
The finding shouldn’t be surprising; many of modern medicine’s most powerful antibiotics have been stolen from microbes. The little critters use the drugs to defend themselves against other microbes and compete for peat and resources. But as bacteria develop resistance, causing an urgent public health crisis, scientists are looking for new drugs to appropriate. In their search, many scientists turned to searching exotic soils and sediments. They assumed that the molecular weapons of bacteria closest to us had already been drained. But as more researchers delve into the complex microbial communities within us – our microbiomes – they are finding new depths to plumb.
The study isn’t the first example of scientists looking for new drugs. As Ars reported in July, researchers found another MRSA-killing antibiotic among bacteria battling boogers in the nose. In the new study, researchers from Rockefeller University and Rutgers University dug into the depths of our guts.
As is often the case, the researchers were unable to grow the microbes that live in our guts for their research. (Scientists have yet to find the right conditions and resources to grow the vast majority of microbes in labs, which are very different from their natural environment.) Instead, the researchers delved into the genetic sequences of the microbes — which can be deciphered without having to grow them – and tried to find unique codes for large peptides that could be antibiotics. They found 25 such sequences and used the code to make synthetic compounds.
Two of them turned out to be antibiotics called humimycin A and humimycin B. The two drugs, derived from related DNA sequences in Rhodococcus equi And R. erythropolis bacteria, can kill both pathogenic and harmless gut microbes. MRSA strains could survive much higher doses of the two drugs, but they predisposed the resistant microbes to a different class of antibiotics called β-lactam. When researchers infected 10 mice with MRSA and gave them only a β-lactam antibiotic, only two survived for 48 hours. In another group of 10 that the scientists treated with humimycin alone, only five survived. But with a combination of a β-lactam and humimycin, all mice survived.
While the data suggests that humimycins could be a new treatment regimen, the researchers’ traces could be a path to even more antibiotics. “We believe this approach will enable broad and rapid access to diverse bioactive compounds inspired by gene clusters found in the ever-growing pool of microbial sequence data,” they concluded.
Nature Chemical Biology2016. DOI: 10.1038/nchembio.2207 (About DOIs).