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New treatment through old treatment
Phage therapy has been known since the 1920s and has already been used extensively, for example in Georgia. Phages are special viruses that infect and destroy bacteria. Thus, they represent a potential therapy against bacterial infections in which antibiotics do not work. Up to now, the disadvantage of phages was that the treatment was rather uncontrolled and the consequences were not always foreseeable. Controlled phage therapy is now to change this.
Researchers at the University of California (UC Santa Barbara) developed controlled phage therapy that targets drug-resistant bacteria while avoiding possible unintended consequences. The new phage treatment was recently presented in the renowned journal “Proceedings of the National Academy of Sciences” (PNAS).
The end of the antibiotic age is approaching
The fight against drug-resistant pathogens is becoming increasingly intense. A report by the United States Centers for Disease Control (CDC) showed in 2019 that new forms of drug-resistant pathogens are emerging. At the same time, fewer and fewer options are available to ward off these germs. Doctors and scientists are already talking about the end of the antibiotic age.
Researchers lose race against antibiotic resistance
"We knew early on that it would be a problem," emphasizes Irene Chen, professor of chemistry and biochemistry at UC Santa Barbara. Basically, it has been known since the discovery of penicillin that there are resistant bacteria. Today, resistant organisms such as gram-negative bacteria multiply faster than antibiotics can be developed to combat them.
New hope through well-known alternatives
In search of antibiotic alternatives, Chen’s research team turned to bacteriophages, a naturally occurring group of viruses that colonize and destroy bacteria. "It is their natural function to grow on bacteria and kill them," explains the professor.
"Phage therapy is not new," said Chen. In fact, it has been used in the former Soviet Union and Europe for about a century, although it is widely regarded as the last alternative to antibiotics.
Answer unresolved questions
One of the unresolved questions of phage therapy is the incomplete characterization of phage biology. According to the researchers, phage treatment can have unintended consequences due to the rapid evolution and reproduction of the phages. In addition, there is a risk that the viruses will cause toxins. That is why phage therapy has so far been based on the motto: all or nothing.
"It is difficult to analyze the effects of phage treatment," explains the biochemist. You could either see that it worked completely or completely fail, but you didn't have the kind of dose response you wanted.
The first photothermal phage therapy
To master these challenges, the team developed a method for controlled phage therapy. The researchers were able to use the bacteriophage's ability to colonize only certain bacteria without harming the rest of the microbiome. With a combination of gold nanorods and near-infrared light, even multi-resistant bacteria could be destroyed without antibiotics.
"We conjugated the phages to gold nanotubes," Chen said. These so-called “phanorods” were applied to bacteria on in vitro cultures of mammalian cells and then irradiated with near-infrared light. “When these nanorods are stimulated by light, they translate the energy from light into heat,” continues the professor. This creates very high local temperatures.
Phages colonize the bacteria and are then killed
According to the study, the heat is sufficient to kill both the bacteria and the phages. In this way, the phages can be prevented from developing in an uncontrolled manner. In this way, dosing control is possible. Bacteria of the type E. coli, P. aeruginosa and V. cholerae could be destroyed in the laboratory. The phages also act against X. campestris, a bacterium that causes putrefaction in plants. (vb)
Author and source information
This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
Graduate editor (FH) Volker Blasek
- UC Santa Barbara: A New Old Therapy (accessed: January 14, 2020), news.ucsb.edu
- Irene A. Chen, Huan Peng, Raymond E. Borg, et al .: Controlled phage therapy by photothermal ablation of specific bacterial species using gold nanorods targeted by chimeric phages, PNAS, December 2019, pnas.org