A novel antibiotic — lugdunin — produced by a bacterium found inside the human nose has been found to kill the bacterium Staphylococcus aureus, including drug-resistant forms such as the methicillin-resistant S. aureus (MRSA). The study found S. aureus does not develop resistance against the novel antibiotic. The findings could aid the development of new therapies for hard-to-treat bacterial infections. The results were published today (July 28, 2016) in the journal Nature.
The human body is home to an immense variety of microorganisms known collectively as the microbiota. Several bacteria species including Staphylococcus are found inside the human nose and these bacterial species are fewer in number when the pathogenic S. aureus bacterium is present. However, in about 70 per cent of human population, colonisation by S. aureus inside human nose is absent. The reasons for this were not clear.
On screening a collection of nasal Staphylococcus species for antimicrobial activity against S. aureus, a team of scientists led by Andreas Peschel from the University of Tubingen, Germany, found that Staphylococcus lugdunensis bacterial strain had a particularly strong capacity to prevent the growth of S. aureus.
On screening S. lugdunensis mutants, Dr. Peschel and colleagues identified the compound that resisted the growth of S. aureus and called it lugdunin. Lugdunin causes the breakdown of S. aureus.
The novel compound represents the first known example of a new class of peptide antibiotics.
The lugdunin’s role in inhibiting S. aureus growth was first proved in the lab. To test the efficacy in animals, the researchers infected mice skin with S. aureus and then treated it with the novel antibiotic 24, 30 and 42 hours after infection had set in. Lugdunin was found to completely clear all viable S. aureus from the surface and in the deeper layers of the skin.
Next, lugdunin’s ability to inhibit S. aureus’ growth in the nose was tested using cotton rats. When both S. aureus and S. lugdunensis bacteria were introduced into the cotton rat nose, relatively fewer S. aureus cells were retrieved proving that lugdunin production effectively prevented S. aureus colonisation inside the nose.
The nasal swabs of 187 hospitalised patients were tested for the presence of S. aureus, S. lugdunensis or both. When both the bacterial species were found in a patient’s nose, S. aureus colonisation was nearly six times lower than in those people who had only S. aureus.
The researchers found lugdunin had bacterial activity against many major pathogens, and S. aureus isolates had “pronounced susceptibility” to lugdunin in all nasal and clinical samples. So it may be quite difficult for S. aureus to develop resistance against lugdunin, they say.