It's not a toy
The spinner was turned into an express test for the diagnosis of urinary tract infections
Vyacheslav Gomenyuk, N+1
Scientists have created an express test for the diagnosis of infections of the urogenital tract, resembling a spinner - for the test to work, it literally needs to be twisted in the same way as a regular spinner. The development is described in an article published in the journal Nature Biomedical Engineering (Michael et al., A fidget spinner for the point-of-care diagnosis of urinary tract infection). So far, the test has been used with only one of the strains of E. coli.
According to WHO, urinary tract infections are the second most common after inflammatory diseases of the upper respiratory tract. Due to anatomical features (wide and short urethra), women are more likely to suffer from these infections - it is believed that every second woman under the age of 32 carries some form of this infection. The treatment of these diseases costs healthcare systems millions of dollars, and patients often do not follow the recommendations of doctors well. This is due to many reasons, among which we can single out a long diagnosis of infection and the rapid development of an asymptomatic chronic process against the background of irrational antibiotic therapy.
In the treatment of urinary tract infections, doctors prescribe broad-spectrum antibiotics that can kill several types of bacteria at once. This approach is used to relieve acute symptoms of infection and accelerate recovery. For example, with pyelonephritis, which is accompanied by pain in the lumbar region and high fever, antibiotics active against E. coli (E. coli) are prescribed, since this particular bacterium most often causes these diseases. On the one hand, this makes it possible to alleviate the patient's condition, and on the other hand, the risk of deterioration of the patient's condition or the development of resistance increases if the disease is caused by another microorganism. But doctors take this risk, since the absence of treatment for 2-3 days, which are required to study the resistance of the microorganism to antibiotics, threatens complications in acute infection.
Therefore, to improve the quality of treatment, a faster method of studying the microorganism is needed. To date, the standard method for diagnosing urinary tract infections is the detection of bacteria in the patient's urine with a further bacteriological culture method, in which a urine sample is sown on a nutrient medium. This study requires a lot of time (the same 2-3 days), resources (laboratory equipment) and labor costs. It is not possible to carry out such an analysis in primary health care institutions, especially in developing economies.
A group of researchers led by Issac Michael from the National Institute of Science and Technology in Ulsan has created a cheap and easy-to-use device that allows you to detect bacterial cells in a urine sample. The test result will be available in 50 minutes, and if you spend another 70 minutes, you can investigate the resistance of the strain to antibiotics. The test system takes up no more space than a regular spinner (and rotates the same way) and is available for use on an outpatient basis.
Drawings from the article by Michael et al.
The test system is a plastic plate with a hinge in the middle. There is a recess with a hole on the side of the hinge – it is here that urine samples (one milliliter) are injected. Even closer to the edge is the filter membrane (white circles). Between the recess and the membrane there is a sampling chamber through which a urine sample enters the filter. With the help of centrifugal force caused by rotation and a special buffer solution, bacteria are distributed evenly across the filter membrane, which allows them to be filtered out of urine, distributed in an even thin layer and at the same time maintain the initial concentration of microorganisms. To achieve the desired effect, it is necessary to run the rotation of the system around the hinge twice with your finger.
After filtration, a solution with the chemical substance WST-8 (tetrazolium dye) is added to the system. When it interacts with the enzymes of the respiratory chain, which is located in bacteria directly on the cell membrane, the dye is restored with the formation of formazams (derivatives of formic acid) having an orange color.
The higher the concentration of the microorganism in the sample, the richer the color will be. To get a reliable result, the device must be placed in an incubation cabinet for 45 minutes at a temperature of 37 degrees Celsius. So, the test turns bright orange at a bacterial concentration of 10 6 ml-1, which allows you to calculate the dose of the antibiotic and make a forecast.
To find out if the strain is resistant to an antibiotic, you can use the second half of the plate, on which the elements described above are symmetrically arranged. To do this, a new urine sample is mixed with the studied antibiotic and left for twenty minutes. The resulting mixture is injected into the device, filtered by rotation, WST-8 is added and incubated under similar conditions. If the microorganism is resistant to an antibiotic, there will be the same picture as at the first detection – the orange color of the indicator at the appropriate concentration. If the strain is susceptible to an antibiotic and the bacteria die, then their concentration decreases, and this can be seen by the absence of staining – the filter membrane will remain white.
Scientists examined urine samples in which E. coli was found. Samples were taken from 39 patients with various forms of urinary tract infection. The detection (detection) and concentration of bacteria were monitored in comparison with the bacteriological method. During the bacteriological examination, the diagnosis was confirmed (bacterial concentration >10 3 ml-1) in 41 percent of patients. When using the new test system, this figure was 46 percent. In a detailed study, the scientists revealed two false positive results associated with the reaction of the indicator with a large number (more than 15 in the field of view) of red blood cells in one patient and white blood cells in another. This limits the use of the new method for patients with high rates of erythrocytes and leukocytes in the urine.
The control of the Escherichia coli resistance study was carried out using two antibiotics – ciprofloxacin (CIP) and cefazolin (CZ). Scientists studied sensitive (S) and resistant strains to both drugs in low and high dosages. The intensity of the orange color varied depending on the concentration of the microbe in the sample: if the antibiotic worked and the concentration decreased, there was a decrease in the intensity of the orange color. In 95 percent of cases, the determination of resistance was correct compared to the bacteriological method.
Thus, instead of one or two days to grow the crop and another one or two days to determine the sensitivity of the strain to various antibiotics, it takes a couple of hours to accurately diagnose the infection. All this in the future will allow doctors to improve the standards of care in this area and reduce the percentage of misuse of antibiotics. The analysis using the new test system is much cheaper than the classical bacteriological analysis (the authors do not name the exact cost) and does not require additional resources, except for the incubation cabinet, which allows it to be used with limited resources. The authors note that the test is not aimed at identifying the pathogen. It helps to determine the concentration of microorganisms to confirm the diagnosis and to study the resistance of the strain to the antibiotic.
The system was tested only on E. coli. Additional studies are needed with other common pathogens of urinary tract infections (Klebsiella pneumoniae and Proteus mirabilis).
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