Etiological Structure of Lower Respiratory Tract Pathogens in Treatment and Rehabilitation of Patients with Chronic Critical Illness in Intensive Care Units

BACKGROUND: Chronic critical illness is characterized by ventilator dependence, systemic inflammatory response, multiorgan failure, secondary sarcopenia, hypermetabolism and hypercatabolism, and protein–energy malnutrition. In this category of intensive care unit patients, lower respiratory tract infections remain a significant cause of adverse outcomes, prolonged hospital stays, and increased treatment costs. It is impossible to provide adequate empirical treatment of lower respiratory tract infections without knowing the etiology and resistance of the leading pathogens of this nosocomial infection in a specific department of a healthcare organization.

AIM: The study aimed to characterize the etiology of lower respiratory tract infections in intensive care unit patients from 2020 to 2023, determine their antibiotic susceptibility, identify the most common resistance mechanisms of leading pathogens, and provide recommendations for optimizing antimicrobial therapy.

METHODS: The study included patients with confirmed lower respiratory tract infections, primarily those with prolonged or chronic critical illnesses, from 2020 to 2023. The BD Phoenix 100 automated analyzer was used to identify the pathogens. Susceptibility was interpreted using EUCAST criteria.

RESULTS: From 2020 to 2023, the top 10 pathogens responsible for lower respiratory tract infections in 1,007 patients were predominantly gram-negative microorganisms. For this period, the following trends were noted: an increase in Acinetobacter baumannii from 13.22% to 21.40% (p < 0.001), and a decrease in Escherichia coli from 7.90% to 2.98% (p < 0.001). From 2020 to 2023, the resistance of Klebsiella pneumoniae and Acinetobacter baumannii to carbapenems increased significantly, from 80.50% to 91.64% (p < 0.001) and from 89.89% to 98.14% (p < 0.001), respectively. Among carbapenemase-producing Klebsiella pneumoniae, resistance to colistin, tigecycline, and ceftazidime + avibactam increased from 4.95% to 9.00% (p < 0.001), from 48.76% to 71.28% (p < 0.001), and from 33.06% to 47.73% (p = 0.041), respectively.

CONCLUSION: The predominant pathogens causing lower respiratory tract infections in intensive care unit patients included Gram-negative bacteria with a high level of antibiotic resistance. These bacteria included carbapenem-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The etiological structure of lower respiratory tract infections and their antibiotic susceptibility in these patients should be evaluated to create local protocols for effective empirical antimicrobial therapy in each specific intensive care unit of a healthcare organization.