Superantibiotic against superbugs

Antibiotic from the soil

Alexandra Bruter, Polit.roo

A group of German-American scientists described a fundamentally new antibiotic – theixobactin – and not anywhere, but in the journal Nature (Ling et al., A new antibiotic kills pathogens without detectable resistance). Even more than that: the authors have not just found a new antibiotic, they have found a new way to look for new antibiotics.

In fact, this method is not so new. It looks amazing, but since the mid-60s, only one new group of antibiotics has appeared. All the others were actually discovered in the first two decades. The era of antibiotics was opened by penicillin, which was slowly being born, and over the next 20 years all the other antibiotics that we use now were discovered.

All these antibiotics were found in about the same place. They are produced by other bacteria. In fact, man began to fight infections with precision quite recently, using scientific methods – about a century and a half, if you count from Pasteur and Lister. The human immune system learns to resist bacteria all the time that a person lives next to bacteria, exactly as long as a person exists as a species (about 200 thousand years). 200,000 years is, of course, much more than two hundred years, but the bacteria themselves have existed for about 3.5 billion years and have been competing with each other all this time. It is clear that under such conditions, other bacteria are best able to kill bacteria.

Indeed, most of the existing antibiotics are of bacterial origin. The antibiotic boom of 50 years ago we owe to Selman Waxman, who tested soil bacteria that he managed to maintain in laboratory culture. So streptomycin and neomycin appeared.

Surprisingly, scientists' attempts to synthesize antibiotics artificially have not borne much fruit. And so it turned out that bacteria gradually began to win the arms race. If you act on bacteria with an antibiotic for a long enough time, then all bacteria sensitive to the antibiotic will die: someone earlier, someone later. That is why it is important to always take a course of antibiotics to the end, and not quit after feeling an improvement. But if a mutation has occurred in any one bacterium that makes it insensitive to an antibiotic, then the antibiotic will not kill it, and its competitors will disappear. If at the same time she is lucky enough to deceive the immune system, then the carrier of the disease will not be lucky.

The rate of mutations in bacteria is quite high, and it further increases under stressful conditions. An antibiotic is just such a stressful condition. It is clear that if everyone around is dying anyway, then it is beneficial to mutate: if the mutation turns out to be harmful, then it will not be worse anyway, but it may be useful. Therefore, quite a lot of antibiotic-resistant bacteria have appeared in recent years. At first they lived only in hospitals, but gradually they got out to freedom. A resistant variety of Acinetobacter baumannii turns out to be the cause of non-healing wounds. Tuberculosis is returning to the positions it was handed over a century ago thanks to resistant strains. The news of the appearance in the medical institution of MRSA (a strain of Staphylococcus aureus, resistant to methicillin and other penicillin antibiotics, and at the same time to cephalosporins) can accelerate the growth of gray hair in the entire management staff.

The first crop of antibiotics had already been removed from soil bacteria, but there was still hope that there would be something else there. This hope is due to the fact that until now, about 1% of the total variety of soil bacteria have been able to grow in laboratory conditions. The authors of the article have just developed a method that allows cultivating about 50% of soil bacteria instead of 1%. The essence of this method is that in capillaries with semi–permeable walls made of a special material, the bacteria were immersed in the natural environment - in the soil. Having multiplied in such conditions, then the bacteria could already live for some time in ordinary laboratory dishes, where it was easier for scientists to study them. It turned out that the extract of one of the species of bacteria analyzed dealt well with Staphylococcus aureus. To isolate the active substance was already a matter of technique. The substance was named teixobactin. The authors do not indicate this anywhere, but probably the name comes from the Greek word teixos, meaning "fortress wall". The new antibiotic prevents bacteria from synthesizing the cell wall. Such a bacterium cannot divide (for this it is necessary to synthesize a new whole wall) and cannot even patch up the gaps that arise from time to time.

The structure of theixobactin (Wikimedia Commons)

Teixobactin proved effective against a wide range of bacteria: staphylococci (including MRSA), streptococci that cause lung inflammation, mycobacteria that cause tuberculosis, the causative agent of anthrax and others. But the most surprising thing is that attempts in the laboratory to remove Staphylococcus aureus and Mycobacterium tuberculosis, resistant to theixobactin, were unsuccessful. This means that for a while a new antibiotic is likely to be able to reverse the course of the arms race between bacteria and antibiotics. It is unlikely that the discovery of only one teixobactin will provide an advantage for a long time – to stay in place in this confrontation, you need to run very fast. But there are still quite a lot of unexplored bacteria living in the soil.

Portal "Eternal youth" http://vechnayamolodost.ru 12.01.2015