A new antibiotic that can kill
meticillin-resistant Staphylococcus aureus (MRSA) has been discovered in the
human nose by researchers at the University of Tübingen in Germany.
The novel molecule lugdunin, which is
produced by the bacterial species Staphylococcus lugdunensis, was isolated from
samples of human nasal bacteria. In laboratory tests, the researchers
discovered it was able to kill a number of harmful bacteria that are resistant
to other antibiotics, including vancomycin-resistant enterococci, glycopeptide
intermediate-resistant S. aureus and MRSA.
Although usually harmless, S. aureus is
present in the nasal passages of 30% of the population. It can become invasive
and cause deadly blood infections, especially in people with weakened immune
systems. Using antibiotics like mupirocin to remove S. aureus colonies can
substantially reduce the chance of infection, but with antibiotic resistance a
growing threat to human health, alternative strategies are needed.
To find out how 70% of the population resist
colonisation with S. aureus, the research team collected nasal swabs from 187
hospitalised patients. They
hoped that analysing human bacteria would lead them to more fruitful
discoveries of antibiotics, which are usually isolated from soil bacteria.
Of the nasal swabs collected, the researchers
found that 9.1% of those colonised with S lugdunensis had much lower levels of
S. aureus. Only 5.9% of these swabs were colonised with S. aureus, compared
with 34.7% of the swabs that were not colonised with S. lugdunensis.
This is the first time an antibiotic has been
isolated from a human-associated bacteria. Andreas Peschel, from the department
of infection biology at the University of Tübingen, says the discovery was
“totally unexpected”.
The researchers also found that S. aureus
bacteria did not develop resistance to lugdunin, even with exposure already
having occurred in people and in repeated exposure in the laboratory. “It seems
[lugdunin] can’t develop resistance,” says Bernhard Krismer, a postdoctoral
researcher in the department of infection biology at the University of
Tübingen.
In mice, lugdunin applied topically was able
to either partially or totally eradicate skin infections caused by S. aureus.
The team now hopes to partner with a pharmaceutical company to see if the
antibiotic can be used to clear S. aureus colonies in people.
The researchers believe that the drug might
be able to be taken systemically, because it did not exhibit any signs of
toxicity on a sample of human serum. However, lugdunin is not very soluble in
water, meaning it might be hard for the body to absorb it. The researchers say
the chemical structure might need to be modified to make it suitable for
systemic use.
The discovery may also help in the
development of new probiotics, suggest the researchers. However, since S.
lugdunensis can itself cause opportunistic infections, it is an unsuitable
candidate for use as a probiotic. Therefore, the team suggests that the genes
from this species could be introduced into a harmless bacterial strain instead.
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