Nose-dwelling microbes produce an antibiotic which kills the hospital superbug MRSA, scientists have discovered. The finding suggests that the human body might harbour a rich variety of bacteria that could be harnessed in the fight against antibiotic resistance.
Antibiotic resistance is a growing cause for concern, with experts warning of an impending “apocalyptic” situation in which patients die following routine surgery because of infections that can no longer be treated. Among the superbugs of concern are strains of Staphylococcus aureus that are resistant to a number of antibiotics; these strains are known as MRSA.
Now scientists say they have discovered a bacterium lurking in the nose that fights MRSA by producing its own antibiotic.
Andreas Peschel, co-author of the study from the University of Tübingen, described the discovery as “totally unexpected”, as most antibiotics in use have come from soil bacteria.
The finding, Peschel adds, opens up a new preventative approach to tackling bacterial infections. One possibility, he says, is that harmless bacteria could be genetically modified to produce the new antibiotic, and then introduced to patients carrying S.aureus. That, the authors note, could prove a boon, as resistance is growing towards existing antibiotics used to kill off MRSA in patients awaiting surgery.
Published in the journal Nature by scientists from the University of Tübingen, the research reveals how the new antibiotic was discovered following the analysis of nasal swabs from 37 individuals.
With around 30% of humans carrying S.aureus in their nostrils, increasing their risk of infection after surgery or illness, the team scanned bacteria from the swabs to explore whether other nasal-dwelling microbes were putting up a fight.
The results reveal that a strain of the bacterium Staphylococcus lugdunensis can kill off S.aureus, even when it is outnumbered ten to one. That, the researchers found, is down to the production of an antibiotic, named lugdunin. Moreover, further investigations revealed that the genes necessary for the production of lugdunin appear to be present in all strains of S.lugdunensis.
“It’s really the first human-associated bacterium where the whole species is able to produce such an antibiotic,” said Bernhard Krismer, another co-author of the study.
As well as killing off a range of S.aureus strains, the new antibiotic defeated a host of other bacteria, including Streptococcus pneumoniae, which can cause meningitis and bronchitis among other conditions. Lugdunin also killed strains of Enterococcus, a bacteria that can cause inflammation of the heart, urinary tract infections and bloodstream infections, that are resistant to the antibiotic vancomycin.. What’s more, when applied to mice, the new antibiotic was found to clear or reduce skin infections of S.aureus.
To probe whether humans carrying S.lugdunensis had a lower chance of carrying S.aureus as well, the team collected a further 187 nasal swabs from hospital patients. The results revealed that the percentage of patients who carried S.aureus was almost six times lower for those who carried S.lugundensis (17 patients) than for those who did not.
“This [research] is showing that same competition that happens in the soil - where bugs are trying to kill each other to gain space and access to niches and habitats - is happening in the body,” said Mark Webber, co-head of the Antimicrobials Research Group at the University of Birmingham, who was not involved in the study.
Scientists say the new research adds weight to the idea that the human body itself could offer up new possibilities in fight against antibiotic resistance. While S.lugundensis can itself cause infections, the authors say one approach would be to insert the genes for the new antibiotic into harmless bacteria which could then be introduced to humans. Alternatively, lugdunin itself could eventually be produced commercially.
But there is a drawback: the newly discovered antibiotic only kills gram-positive bacteria, a type of bacteria that lacks an outer cell membrane. “It doesn’t have any activity against gram-negative bugs, things like E. coli,” said Webber. “Those are the ones that are causing most of the infections and are the hardest to treat.”
While Webber agrees that the new discovery could open up a fresh avenues for tackling antibiotic-resistance, he warns that lugdunin is “a million miles away from being a useful drug”, adding that antibiotics typically take decades to develop.
Despite the lengthy wait, the University of Tübingen has already applied for a patent for the new antibiotic. And there may be more discoveries to come from the human-dwelling bacteria, believes Peschel. “Lugdunin may be just the first example of such an antibiotic,” he said.
- This article was edited on 28 July to correct a possible ambiguity. To clarify: only certain strains of Staphylococcus aureus are known collectively as MRSA (methicillin-resistant Staphylococcus aureus).
