Resistance to antibiotics can be drawback for bacteria

Meningococci are usually harmless bacteria, and about one person in ten carries them in their throats or airways without knowing it. But they can also make their way into the blood and through the blood-brain barrier and cause blood poisoning and/or meningitis, and then the fatality rate is high, about 10 percent.

It has therefore been disturbing to see reports from most countries in recent years that meningococci have also begun to be more resistant to antibiotics. But now Sara Thulin Hedberg can establish in her doctoral dissertation in biomedicine that this is not the case in Sweden at present. Even though some of the bacteria have become resistant to individual preparations, they have not increased in number and do not seem to be spreading in society.

"We expected a more negative tendency, considering the dramatic increase in resistant bacteria in society, so these findings are both a surprise and a great relief," she says.

Since meningococci are very good at adapting, using their ability to pick up parts of DNA from other bacteria in the same family, for instance, they have every chance of rapidly changing and developing resistance. But Sara Thulin Hedberg’s research indicates that the biological cost is too great for the bacteria. In other words, it is not a formula for success to become resistant.

When she studied meningococci that had become resistant to rifampicin, an antibiotic, she discovered that they do not multiply as rapidly and are not as good at infecting a host. They are quite simply somewhat weaker and not as good at reproducing. This means that they have a hard time competing with susceptible meningococci as soon as they find themselves in an antibiotic-free environment.

The findings from Sara Thulin Hedberg’s research may ultimately open new potential for combating resistant bacteria.

"By enhancing our knowledge of how bacteria change and are affected by developing resistance it may be possible to design antibiotics that bacteria find it more difficult to adapt to without excessive cost to themselves."

Sara Thulin Hedberg works at the National Reference Laboratory for Pathogenic Neisseria at Örebro University Hospital, and she has mapped what happens at the genetic level when meningococci change and develop increased resistance to antibiotics. She has studied lines of meningococci from Sweden and Africa and has also carried out part of her research at the Pasteur Institute in Paris.

Sara Thulin Hedberg presents her findings in her doctoral dissertation titled Antibiotic susceptibility and resistance in Neisseria meningitidis – phenotypic and genotypic characteristics.

For more information, please contact Sara Thulin Hedberg, phone: +46 (0)19-602 15 20, e-mail: sara.thulin-hedberg@orebroll.se.

Pressofficer Ingrid Lundegårdh, ingrid.lundegardh@oru.se;+46-705 52 31 26
(idw, 01/2010)

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