Microbiological monitoring of COVID-19 patients in the ICU: a prospective observational study

Objective. To study spectrum of pathogens and the time to colonization of respiratory samples in patients with severe and critical COVID-19 as well as to analyze incidence of nosocomial infections and structure of prescribed antibacterial drugs. Materials and Methods. The prospective observational study included patients aged 18 years and older with confirmed severe and critical COVID-19 from December 2021 to February 2022. During the first 48 hours and then every 2–3 days of hospitalization, a respiratory sample was collected: sputum, tracheal aspirate (if intubated), bronchoalveolar lavage (if bronchoscopy was performed) for microscopy and microbiological examination. Some patients were screened for invasive aspergillosis. Clinical and demographic data, comorbidities, pathogenetic therapy for COVID-19, antibiotic therapy, cases of probable/documented bacterial nosocomial infections, antibiotic-associated diarrhea, and hospital treatment outcomes were recorded. Results. A total of 82 patients were included in this study. Patients with lung parenchyma involvement of more than 50% by computer tomography predominated; most of them (77%) required intubation and mechanical ventilation due to progression of respiratory failure, and 76% of patients had a lethal outcome. During the first 48 hours, a respiratory sample was obtained from 47 patients; the rest of the patients presented with non-productive cough. No growth of microorganisms was detected in 31 (36.8%) cases; clinically significant pathogens were detected in 16 (19.5%) patients. A subsequent analysis included data from 63 patients with a sufficient number of samples for dynamic observation were used. During the first 3 days of ICU stay, the most common bacterial pathogens were Klebsiella pneumoniae without acquired antibiotic resistance and methicillin-susceptible Staphylococcus aureus. From 3rd day and afterwards, an increase in the proportion of Acinetobacter baumannii, other non-fermenting bacteria, and carbapenemresistant Enterobacterales was noted. Among the pathogens causing lower respiratory tract infections, A. baumannii and carbapenem-resistant K. pneumoniae were predominant pathogens and accounted for 76% of cases. Positive galactomannan test results were obtained in 4 cases. Conclusions. The study confirmed importance of bacterial nosocomial infections in patients with severe and critical COVID-19. In the case of the development of nosocomial lower respiratory tract infections, empirical antimicrobial therapy should take into account the predominance of carbapenem-resistant Enterobacteria and A. baumannii, as well as the possibility of invasive aspergillosis.