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BACKGROUND: In recent years, there has been a catastrophic increase in the resistance of bacterial strains to antibacterial drugs. The spread of the novel coronavirus disease (COVID-19) pandemic has led to the overuse of antibiotics, which has led to an even greater spread of resistant strains in hospitals. Given the accumulated positive experience in using bacteriophages, it is advisable to use them in patients after determining the sensitivity of each strain of isolated bacteria to bacteriophages. Since Klebsiella pneumoniae was the most frequently isolated bacteria in complicated forms of COVID-19, it became necessary to determine the sensitivity of these and other gram-negative bacteria to the corresponding bacteriophages. AIM: This study aims to reduce the time for determining the sensitivity of an isolated microorganism culture to bacteriophages by developing an express method. MATERIALS AND METHODS: The study used 30 strains of pan-resistant Gram-negative microorganisms from the collection of the Museum of the Laboratory of Medical Bacteriology of the Pasteur Research Institute of Epidemiology and Microbiology in St. Petersburg: Klebsiella pneumoniae (n=10), Escherichia coli (n=10), Pseudomonas aeruginosa (n=10), and also preparations of bacteriophages manufactured by JSC NPO Microgen: Bacteriophage Klebsiella polyvalent purified; Bacteriophage coliproteus; Pseudomonas aeruginosa bacteriophage. RESULTS: Of the strains studied, 4 out of 10 studied K. pneumoniae strains, 6 out of 10 E. coli strains, and 7 out of 10 P. aeruginosa strains were susceptible to polyvalent bacteriophage preparations. Reliable results were obtained 3 hours after the sensitivity of isolated cultures to bacteriophages was established, which is undoubtedly the most important finding of the study. CONCLUSION: The developed method for determining the sensitivity of gram-negative bacteria to bacteriophages enables reducing the study time by 6 times (up to 3 hours), which affects the timing of etiotropic therapy selection with bacteriophages for each patient.

Brucellosis is an infectious particularly dangerous zoonotic disease caused by bacteria of the genus Brucella, among which B. melitensis, B. abortus, and B. suis have pathogenic potential, causing a severe and often chronic course of the disease. Laboratory diagnostics is crucial for the detection of human cases, since the clinical symptoms of human brucellosis are variable and nonspecific. Laboratory diagnosis of brucellosis is based on three different approaches: direct bacteriological method, indirect method using serological and allergic tests and direct express method in different formats of molecular polymerase chain reaction. Despite the accumulated experience of using serological tests and the highly sensitive polymerase chain reaction method, the isolation of Brucella culture is considered the gold standard in the laboratory diagnosis of brucellosis due to its clinical and epidemiological relevance. The currently available automated systems of the bacteriological method have increased its sensitivity and shortened the detection time of Brucella species. The main limitations of serological tests are the lack of general interpretation criteria, low specificity due to cross-reactions with other bacteria and low sensitivity at an early stage of the disease. At the same time, in Russia, serological tests account for more than 99% of all laboratory tests and remain the main diagnostic tool. This is due to their inexpensive and convenient use at the place of medical care in endemic areas and high negative prognostic value. Polymerase chain reaction in various formats of rapid tests diagnoses the DNA of the pathogen in a few hours with high sensitivity and specificity. Nevertheless, a positive polymerase chain reaction result requires careful interpretation and does not necessarily indicate an active infection. For the convenience of using diagnostic approaches to brucellosis in practical medicine and determining the activity of the infectious process, it is necessary to improve diagnostics and develop express methods. The review shows both the most routine and modern laboratory methods currently available for laboratory diagnosis of brucellosis.