E.V. AGAFONOVA^1, 2, I.D. RESHETNIKOVA^1, 3, L.T. BAYAZITOVA^1, 2, E.V. KHALDEYEVA¹, YU.A. TYURIN^1, 2, G.SH. ISAYEVA^1, 2

 ¹Kazan Scientific Research Institute of Epidemiology and Microbiology, Kazan

² Kazan State Medical University, Kazan

³Kazan (Volga) Federal University, Kazan

 Contact details:

Agafonova E.V. — PhD (medicine), laboratory diagnostics doctor, Assistant Lecturer of the Department of Propedeutics of Children’s Diseases

Address: 67 Bolshaya Krasnaya St., Kazan, Russian Federation, 420015, tel.: +7-917-876-16-44, e-mail: agafono@mail.ru

Antimicrobial strategies of neutrophils play a leading role in the regulation of microbiocenoses. In COVID-19 convalescents, the state of upper respiratory tract and oropharynx microbiota and the functional and the metabolic activity of the MALT system neutrophils were evaluated. Changes in the microbiota composition were characterized by two directions — an increase in colonization by bacterial and fungal pathogens — Staphylococcus aureus, Candida albicans, enterobacteria (Escherichia coli, Klebsiella spp.) and an increase in mixed infection, primarily by 2-component associations of Staphylococcus aureus + Candida albicans. Neutrophils in COVID-19 convalescents were characterized by increased destructive and apoptotic intracellular processes, as well as impaired antimicrobial strategies — inhibition of oxygen-dependent biocidity, rapid depletion of reserve capabilities, incomplete phagocytosis, limited ability to capture and kill pathogens, which determines increased colonization by pathogens and an increase in mixed infection.

Key words: COVID-19 infection, neutrophil, microbiota, antimicrobial strategy.

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