Genetic Markers of Antibiotic Resistance in Pathogens Causing Lower Respiratory Tract Infections in Patients in a Chronic Critical Condition

The aim of this study is to determine the prevalence of antibiotic resistance genetic markers in pathogens causing lower respiratory tract infections in patients with chronic critical illness.

Materials and Methods. We analyzed genetic markers of resistance to antimicrobial agents in pathogens causing lower respiratory tract infections in 251 patients in a chronic critical condition who were admitted to the intensive care unit (ICU) in 2025. Pathogen identification and gene detection were performed using an automated analyzer and the real-time polymerase chain reaction (qPCR) method.

Results. The predominance of three pathogens — Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa — was confirmed; these accounted for more than 40% of the identified infections. It was found that among the identified genetic determinants of resistance, the shv gene (58.35%) was predominant; this gene is responsible for the intrinsic resistance of K. pneumoniae and the acquired resistance of E. coli. The ctx-m-1 gene ranked second in prevalence at 55.80 %, and the tem gene ranked third at 50.29 %. Carbapenemase genes accounted for a significant proportion: ndm genes were detected in 41.45 % of samples, and genes of the oxa family were widely distributed — oxa-48-like was detected in 40.47 % of cases, oxa-40-like in 38.51 %, oxa-51-like in 34.38 %, and oxa-23-like in 18.86 %.

Conclusion. Among patients with chronic critical illness admitted to the ICU, Gram-negative bacteria — including Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa — were the predominant pathogens causing lower respiratory tract infections in more than 40 % of cases. Two or more genetic markers of resistance were detected in 80.55% of the samples. The oxa- 51-like gene was detected in all A. baumannii strains. Carbapenemase genes (ndm, oxa, kpc) and beta-lactamase genes (shv, ctx-m-1, tem) were prevalent.

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