The dissertation provides a theoretical justification and a solution to the current task, which consists of increasing the effectiveness of treatment of patients with community-acquired pneumonia (CAP) and conducting secondary prevention of viral- bacterial community-acquired pneumonia by using the inhaled antiseptic decamethoxin and optimizing diagnostic algorithms for identifying the etiopathogen of this nosology. To increase the effectiveness of identifying the causative agent of CAP, an algorithm for the etiological laboratory diagnosis of pathogens in patients with CAP and its modification – to search for the etiopathogen of CAP during a high prevalence of COVID-19 or influenza – were proposed. The developed algorithm provides for the simultaneous use of three different methodological approaches – classical, rapid and molecular tests for detecting respiratory pathogens. This approach significantly
increases the efficiency of etiological diagnostics of CAP.
A virological study was performed, the results of which expanded the understanding of the antimicrobial spectrum of the drug developed in Ukraine, a representative of the group of quaternary ammonium compounds, decamethoxin.
It was established that the cytotoxic effect of decamethoxin by in vitro studies depends on the type of cell culture, fully realizes during 24 hours after its application to cell monolayers and remains unchanged throughout the observation period up to 72 hours.
By assessing the cytotoxic dose of decamethoxin in the analysis of cell viability using the MTT test, it was established that the CD50 of decamethoxin after 24 h of cultivation, according to the logistic regression model, was equal to 6,34 μg/ml, and after 48 hours – 3,63 μg/ml.
To determine the virucidal effect of disinfectants, we chose the suspension method. It allows the contact of the studied disinfectant with concentrated virus- containing material in a liquid environment, provides an opportunity to simulate the conditions of disinfection of biological fluids, and is relatively safe to perform for laboratory personnel.
It was established that IBV with an infectious titer of 3,0 lg TCD 50 /0,1 ml was completely inactivated by a solution of decamethoxin at a concentration of 0,1 mg/ml (100 μg/ml) during a short exposure – for 30, 60 and 120 seconds at room temperature. At the same time, under the conditions of the smallest exposure of decamethoxin (10 and 20 s), a partial virucidal activity of the antiseptic is observed, which is 1 and 2 lg (TCID 50/0,1 ml) after 24 and 48 h of cultivation, respectively. At the same time, in the control (without decamethoxin treatment), the infectious titer of IBV when cultivated under similar conditions increased from 3,0 to 4,5 and 5,5 lg TCD 50 /0,1 ml after 24 and 48 hours, respectively. In control culture, the monolayer of BHK-21 cells remained without violations of integrity and manifestations of degeneration foci. There were also no manifestations of toxic effects in controls of neutralizer and decamethoxin.
The in vitro virulicidal activity of decamethoxin against IBV coronaviruses was confirmed by the in silico study. The molecular docking of decamethoxin in the active site of the main IBV protease demonstrates the formation of a ligand-protein complex with an estimated binding energy of -8,6 kcal/mol. This ligand-protein complex is stabilized by six hydrogen bonds (2,22 ̶ 3,66Ǻ) with amino acids ASN26, GLY141, GLU187 and GLU164, one electrostatic interaction (3,75Ǻ) with GLU187 and five hydrophobic interactions (53,189Ǻ) with amino acid residues ALA140, CYS143, HIS161 and PRO166.
To evaluate the virucidal effect of decamethoxin against SARS-CoV-2, the similarity of the primary and secondary structures of the main protease of IBV and the main protease of SARS-CoV-2 was investigated in silico, and molecular docking of decamethoxin into the active center of SARS-CoV-2 Mpro was performed.
It was established that the main proteases of IBV and SARS-CoV-2 have 41% sequence identity and 55% sequence similarity. The structural similarity of their active centers has been demonstrated.
The molecular docking of decamethoxin into the active center of SARS-CoV-2 Mpro was performed. The docking shows the formation of a ligand-protein complex by the estimated binding energy of -8,4 kcal/mol. This ligand-protein complex is stabilized by the seven hydrogen bonds (1,94–3,68Ǻ) with amino acids THR24, THR25, ASN142, GLY143, CYS145, HIS164, GLU166, the one electrostatic interaction (4,84Ǻ) with HIS41 and the five hydrophobic interactions (3,81–4,81Ǻ) with the amino acid residues HIS41, CYS145, HIS163. It is necessary to emphasize the formation of hydrogen, electrostatic and hydrophobic bonds between decamethoxine and amino acids of the catalytic dyad HIS41 – CYS145 of the Mpro active site.
