Unlocking the Secrets of the Natural Antibiotic in Our Sweat

Scientists have uncov­ered the atomic struc­ture of the com­pound, enabling them to pin­point for the first time what makes derm­cidin such an effi­cient weapon in the bat­tle against dan­ger­ous bugs.

Although about 1700 types of these nat­ural antibi­otics are known to exist, sci­en­tists did not until now have a detailed under­stand­ing of how they work.

The study, car­ried out by researchers from the University of Edinburgh and from Goettingen, Tuebingen and Strasbourg, is pub­lished in Proceedings of the National Academy of Sciences.

Sweat spreads highly effi­cient antibi­otics on to our skin, which pro­tect us from dan­ger­ous bugs. If our skin becomes injured by a small cut, a scratch, or the sting of a mos­quito, antibi­otic agents secreted in sweat glands, such as derm­cidin, rapidly and effi­ciently kill invaders.

These nat­ural sub­stances, known as antimi­cro­bial pep­tides (AMPs), are more effec­tive in the long term than tra­di­tional antibi­otics, because germs are not capa­ble of quickly devel­op­ing resis­tance against them.

The antimi­cro­bials can attack the bugs’ Achilles’ heel – their cell wall, which can­not be mod­i­fied quickly to resist attack. Because of this, AMPs have great poten­tial to form a new gen­er­a­tion of antibiotics.

Scientists have known for some time that derm­cidin is acti­vated in salty, slightly acidic sweat. The mol­e­cule then forms tiny chan­nels per­fo­rat­ing the cell mem­brane of bugs, which are sta­bilised by charged par­ti­cles of zinc present in sweat. As a con­se­quence, water and charged par­ti­cles flow uncon­trol­lably across the mem­brane, even­tu­ally killing the harm­ful microbes.

Through a com­bi­na­tion of tech­niques, sci­en­tists were able to deter­mine the atomic struc­ture of the mol­e­c­u­lar chan­nel. They found that it is unusu­ally long, per­me­able and adapt­able, and so rep­re­sents a new class of mem­brane protein.

The team also dis­cov­ered that derm­cidin can adapt to extremely vari­able types of mem­brane. Scientists say this could explain why active derm­cidin is such an effi­cient broad-spectrum antibi­otic, able to fend off bac­te­ria and fungi at the same time.

The com­pound is active against many well-known pathogens such as tuber­cu­lo­sis, Mycobacterium tuber­cu­lo­sis, or Staphylococcus aureus. Multi-resistant strains of Staphylococcus aureus, in par­tic­u­lar, have become an increas­ing threat for hos­pi­tal patients. They are insen­si­tive towards con­ven­tional antibi­otics and so are dif­fi­cult to treat. Staphylococcus aureus infec­tions can lead to life-threatening dis­eases such as sep­sis and pneu­mo­nia. The inter­na­tional team of sci­en­tists hopes that their results can con­tribute to the devel­op­ment of a new class of antibi­otics that is able to attack such dan­ger­ous germs.

Dr Ulrich Zachariae of the University of Edinburgh’s School of Physics, who took part in the study, said: “Antibiotics are not only avail­able on pre­scrip­tion. Our own bod­ies pro­duce effi­cient sub­stances to fend off bac­te­ria, fungi and viruses. Now that we know in detail how these nat­ural antibi­otics work, we can use this to help develop infection-fighting drugs that are more effec­tive than con­ven­tional antibiotics.”

Source: University of Edinburgh release