Scientists have discovered a new class of antibiotics that shows promise in treating superbug MRSA, which is resistant to conventional antibiotics.
Led by researchers at Brown University and Rhode Island Hospital in Providence, the team identified two synthetic retinoids with the ability to kill MRSA, or methicillin-resistant Staphylococcus aureus, in mice. Their findings were published on Wednesday in the journal Nature and offer hope of future treatments for antibiotic resistant infections.
Antibiotic resistant infections are on the rise. According to World Health Organisation (WHO) projections, superbugs will outpace cancer by 2050 as the number one killer worldwide. England’s chief medical officer Dame Sally Davies warned last year that widespread antibiotic resistance would signify “the end of modern medicine.”
“This is an emergency,” said Eleftherios Mylonakis, an infectious diseases professor at Brown University’s Warren Alpert Medical School who led the research.
Mylonakis called the situation “frightening,” noting “it affects more than individuals in the hospital or the very ill or the very old. It affects everybody.”
In their research, the team screened 82,000 synthetic compounds and identified those that decreased MRSA’s ability to kill roundworms in the laboratory. Of the 185 compounds that showed some effect, two synthetic retinoids were selected for further study. Retinoids are chemically similar to Vitamin A and are used to treat a variety of conditions including acne and cancer.
Using computer modelling and additional tests, the researchers found that the two substances weakened bacterial cell membranes and killed normal MRSA cells in addition to “persister” cells, dormant cells that are resistant to current antibiotic treatments.
“The molecule weakens the cell membranes of bacteria, but human cells also have membranes,” said William Wuest, an associate professor of chemistry at Emory University who was involved in the research.
In order to minimise the substances’ toxicity to humans while maximising their ability to target MRSA, researchers modified the retinoids. “We found a way to tweak the molecule so that it now selectively targets bacteria,” said Wuest.
Although the new substances showed potential for treating MRSA, they were not effective against other harmful bacteria “for which new antibiotics are badly needed,” according to The Guardian. These bacteria cause a range of illnesses, including gonorrhoea, pneumonia, urinary tract infections, and other diseases.
Mylonakis warned that the development of new antibiotics is failing to keep up with the evolution and spread of resistant bacteria.
“In a simplistic way, it’s a math problem,” Mylonakis said. “It takes the bugs an average of two years to develop resistance to antibiotics. It takes more than 10 to 15 years of work to get an antibiotic into clinical practice.”
Compounding the issue, the development of new antibiotics has stalled in recent years, as several large pharmaceutical companies determined the field is not profitable enough to warrant the significant investment it requires.
“Pharma companies have mostly abandoned this type of research, which has been devastating for the development of new antibiotics,” said Mylonakis.
Mylonakis said the team’s research is helping to fill this gap. He noted that although the team is “extremely optimistic” about their results, “this is still years away from coming to clinical trial.”
“The hope is that we are a step closer to finding a treatment for the most difficult bacteria,” Mylonakis told The Guardian. “The MRSA persisters are resistant to antibiotics and MRSA is both common and very virulent.”
Independent researchers called the findings “remarkable” and noted their promise for the development of new drug treatments, according to The Independent.