Antibiotic-resistant infections are one of the greatest emerging threats to human health. The words create dread in doctors and patients alike and have sent the healthcare field scrambling for solutions. Now, at least one of these efforts is being rewarded. A treatment based on soil-dwelling bacteria has been discovered by a team of researchers using a promising new research method at The Rockefeller University in New York. Their research was published in Nature Microbiology on Monday, Feb. 12.
The researchers discovered a new group of antibiotic agents they dubbed “malacidins,” short for “metagenomic acidic lipopeptide antibiotic-cidins.” They tested the effectiveness of one malacidin, malacidin A, against the antibiotic resistant infection Methicillin-resistant Staphylococcus aureus (MRSA) by infecting the skin of rats with MRSA bacteria and treating the infected sites with the malacidin. Just 24 hours after treatment, the rats’ skin was free of infection.
Following this experiment, researchers sought to determine if bacteria were likely to develop resistance to malacidins. To test this, they exposed MRSA bacteria to sub-lethal amounts of malacidin A for 20 days. After this time, the MRSA did not show any signs of having developed resistance to the malacidin. Whether resistance to malacidins can develop through horizontal gene transfer, where genes are transferred between unrelated bacteria, remains to be seen.
Malacidins are in the same small family of bacteria as another powerful antibiotic agent, daptomycin. This family is known as calcium-dependent bacteria because they require calcium to act as antibiotics. Daptomycin has been in use since 2003 and remained effective against many antibiotic-resistant infections, killing the dangerous cells by disrupting their cell membranes. A few cases of resistance to daptomycin have been reported in recent years. It cannot be used to treat antibiotic-resistant pneumonia because it becomes ineffective when it contacts the pulmonary surfactant found in lungs. However, because of daptomycin’s remarkable effectiveness in combating antibiotic-resistant infections, the researchers decided to look for other calcium-dependent species which they hoped would have similar effects.
In their search for these antibiotic agents, researchers turned to soil and a new research method. They reviewed 2,000 soil samples from diverse environments across the United States using high-speed computer processing to look for chemical markers of calcium dependence, because many of the bacteria could not be effectively cultivated in a lab setting and then examined after growing. They located a particularly promising agent in a sample of desert soil, extracted and cloned the key genes and inserted those genes into a host organism which could multiply quickly in a lab environment. This provided them with enough malacidin to conduct their experiments.
They found that although malacidins and daptomycin are in the same family, they attack bacteria through different methods. Because of this, malalcidins could be used to treat pneumonia, unlike daptomycin, in addition to treating other Gram-positive bacterial infections, including those with antibiotic resistance. The researchers believe the new research method could aid in the discovery of other valuable antibiotics in the future because it enables the identification of promising agents which may have been previously overlooked because their natural forms are difficult to cultivate in a lab.
The possibility of new, effective antibiotics is eagerly welcomed as antibiotic resistance is an ever-growing concern. The CDC states that 23,000 people in the United States die each year due to antibiotic-resistant infections, a number which could be multiplied ten times by 2050 if new antibiotics are not discovered, according to the published study. But, if the method of identifying and producing new antibiotics which discovered malacidins continues to prove effective, we could be well on our way to preventing such an increase and saving lives.
Abbey Bigler is a fourth year English major with minors in business and technical writing, communications studies and biology. ✉ AB842693@wcupa.edu.