Diagnosis for speed
Rapid tests of bacterial infections have been created
Everything is going to the fact that in the near future, traditional diagnostic methods will be replaced by new, modern technologies that allow not only to identify the causative agent of an infectious disease very quickly and accurately, but also to learn a lot of other information about it that is critical for effective therapy.
By bacterial DNA First of all, we are talking about next-generation sequencing (NGS) methods, the relatively high speed of obtaining results and the cheapness of which makes them a more modern alternative to traditional microbiological techniques.
As well as a replacement or an efficiency-enhancing supplement to the fast-acting, but expensive polymerase chain reaction (PCR) method. The principles of NGS operation are based on simultaneous decoding of several sections of the bacterial genome at once.
For example, an interdisciplinary team of researchers from George Washington University (USA) reported in the Journal of Clinical Microbiology about the successful experience of using NGS to identify pathogens that cause pneumonia in patients on a ventilator. The disease develops quite often and can kill an already weakened patient, so urgent diagnosis of infection is literally vital. NGS revealed the DNA of pathogens in 72 percent of bronchial discharge samples. At the same time, the method made it possible to determine the composition and number of microorganisms in the samples much more accurately than standard microbiological methods. The authors hope that NGS technologies will very soon enter into routine clinical practice.
In parallel with American specialists, a group led by Professor Mark Pallen from the University of Warwick School of Medicine (Great Britain) is working on the development and implementation of modern diagnostic methods. Earlier, Pallen and his colleagues used NGS to reconstruct the genome of the causative agent of brucellosis – the bacterium Brucella melitensis. Her DNA was isolated from 700-year-old human bone remains found during excavations in a medieval Sardinian village.
Now scientists have proposed a new approach to the diagnosis of tuberculosis. Today, to diagnose the disease, you need to grow bacteria from a sputum sample (sometimes it takes weeks and months) and examine them under a microscope. This method has not changed since the 1880s. Very often, it is impossible to determine a specific strain of bacteria in a microscope, especially if the infection is mixed.
Pallen and his colleagues were the first to use the "shotgun method" for diagnosis, which scientists use when sequencing long sections of DNA. The essence of the method is as follows. The genome is split into random fragments, which are then sequenced by conventional methods. The overlapping nucleotide sequences obtained in this way are assembled using special programs into a single whole. Using the Illumina MiSeq desktop sequencer, the scientists identified the DNA of the tuberculosis bacterium in all eight sputum samples studied and were able to identify the strain of the pathogen in seven of them. For different samples, the process took from one to two days.
The study was designed to fundamentally confirm the possibility of using the method for the diagnosis of tuberculosis. Now Pallen's group plans to continue exploring its capabilities on a wider range of samples.
By smell And here is an example of a completely different approach to the identification of pathogenic microorganisms.
A team of chemists and microbiologists from the University of Leicester (UK) has developed a method to identify ten different strains of the pathogenic bacterium Clostridium difficile by the combinations of volatile organic compounds (VOCs) they emit.
C. difficile causes severe diarrhea in patients who have been treated with antibiotics in a hospital. Different strains of bacteria vary greatly in their pathogenicity, so a quick and accurate diagnosis is very important. Standard tests do not allow you to quickly identify the strain of the microorganism. At the same time, the combinations of VOCs are unique for each strain. The "smell" of each of them is formed by substances such as methanol, dimethylamine, p-cresol, as well as sulfur compounds. Using a mass spectrometer, the authors identified a total of 69 types of VOCs. Scientists plan to continue working in this direction and create an affordable diagnostic tool that can detect the presence of a certain bacterial strain in the patient's feces almost instantly by a unique "smell", even if the bacteria are represented in a very small amount in the sample.
A bacterium or a virus? Meanwhile, researchers from the Duke University School of Medicine (USA) have developed and successfully tested a technique that allows to find out with 90 percent accuracy the viral nature of upper respiratory tract infection, excluding bacterial infection, and thus avoid the unjustified use of antibiotics.
Unlike current methods that detect traces of specific pathogens in the blood, Geoffrey S. Ginsburg and his colleagues looked at how actively three dozen genes specifically involved in the immune response to acute respiratory viral infection (ARVI) work in blood cells.
Testing of the method on 102 volunteers who were admitted to the hospital's emergency department with an elevated temperature allowed us to establish that 28 of them were infected with a viral infection, and 39 with a bacterial infection. The sensitivity of the method to the presence of the virus was 89 percent, and the accuracy was 94 percent. The results of the analysis were ready in 12 hours, but Ginzburg assures that in the future this time will be reduced.
"In the light of the pandemics of various viruses threatening humanity, it becomes extremely important to diagnose the presence of a viral infection faster and much more accurately than is currently used in clinical practice," Ginzburg notes. "These analyzes require knowledge of which pathogen we are talking about, since they are strain–specific, in order to confirm the presence of infection. Our proposed method can be used when new, previously unknown pathogens appear, including in the case of bioterrorism."
Ginzburg's co-author Christopher W. Woods notes another reason why the technology should be put into practice as soon as possible. "A method that accurately identifies a viral infection in which the use of antibiotics is useless will make it possible to reduce the unjustified use of antibacterial drugs and thereby limit the process of the emergence of increasingly resistant pathogens," Woods believes. The spread of antibiotic resistance in microorganisms is one of the most serious problems that threaten humanity. And scientists from different fields are trying to prevent a catastrophe that most people don't even know about.
Portal "Eternal youth" http://vechnayamolodost.ru25.09.2014