Finding new drugs to treat life-threatening antibiotic-resistant infections is critical to human health, but only one new class – teixobactin – has been discovered in the last 33 years. The World Health Organization has labeled development of such drugs a high priority and in 2015, the Obama administration released an action plan to combat antibiotic-resistant bacteria.
Scientists trawling through thousands of soil samples have discovered a whole new class of antibiotics capable of killing drug-resistant bacteria. The chemical, which has been named malacidin, appears to be non-toxic in humans and is effective in tackling several multidrug-resistant bacteria such as Meticillin-resistant Staphylococcus aureus (MRSA), raising hopes that it could be used to develop new lines of treatment in the never-ending war against antibiotic-resistant pathogens.
The most effective antibiotic drugs so far have come from organisms in the environment that produce antibiotics naturally to defend against bacteria. For instance, penicillin was discovered from a fungus and vancomycin was found in bacteria that lives in dirt. Soil is a good place to look for antibiotics as it is an environment where multiple types of bacteria naturally compete for resources and use a range of exotic chemical compounds to kill each other.
“Environmental microbes are in a continuous antibiotic arms race that is likely to select for antibiotic variants capable of circumventing existing resistance mechanisms,” the authors wrote.
The malacidin chemical, identified by Dr Sean Brady and his laboratory at Rockefeller University, New York, works by attacking a fundamental step in bacterial growth, essentially interfering with a major building block that the bacteria use to build and repair their outer membrane. Initial tests showed that malacidin was not toxic to human cells, and did not induce resistance in S. aureus bacteria, even after 20 days. By comparison, bacteria in the lab have developed antibiotic resistance to the drug rifamycin in a single day.
In their study, published in the journal Nature Microbiology, the authors cautioned that it is only effective against gram-positive bacteria, species that have a very thick cell wall, and therefore, would not be effective against gram-negative bacteria. Nonetheless, the breakthrough suggests there may be more similar compounds like malacidin yet to be discovered in our natural environment.
Research on malacidin has just begun and bringing them to pharmacies will require years of additional research and clinical trials. “The ability to tap into the world’s microbiome in a systematic way could lead to the discovery of new natural products, which historically have been the most productive source of antibiotics so far,” said Brady.
It is also a promising sign that this new class follows closely after the 2015 discovery of teixobactin. Prior to that there had been a 30-year drought, prompting dire warnings of a post-antibiotic apocalypse if bacteria continued to adapt and develop resistance to antibiotics.