Clinical and Microbiological Profile of Hospital-Acquired and Ventilator-Associated Pneumonia in Critically Ill Patients: A Retrospective Observational Study

<b>Background/Objectives</b>: Severe respiratory infections remain a major cause of morbidity and mortality in critically ill patients admitted to an intensive care unit (ICU), particularly in the context of increasing antimicrobial resistance (AMR). This study aimed to describe the clinical, microbiological and resistance profiles of ICU patients diagnosed with hospital-acquired or ventilator-associated pneumonia. <b>Methods</b>: We conducted a retrospective, single-center observational study including adult ICU patients admitted between January and December 2025, with clinically significant positive endotracheal aspirates. Clinical severity scores (APACHE II, SOFA, SOFA-2), inflammatory biomarkers (neutrophil-to-lymphocyte ratio-NLR, platelets-to-lymphocyte ratio-PLR, C-reactive protein-CRP), microbiological findings, antimicrobial resistance patterns and ICU-related outcomes were analyzed. <b>Results</b>: Out of the 606 endotracheal aspirates collected, 76 (12.5%) were culture-positive and 62 (10.2%) patients met the final inclusion criteria. Ventilator-associated pneumonia accounted for 90% of infections, 25 episodes (44.6%) being classified as early-onset and 31 cases (55.4%) as late-onset, without significant differences in bacterial distribution between the two subtypes. In total, 85.5% of infections were monomicrobial, with Gram-negative bacteria representing 76% of isolates. <i>Acinetobacter baumannii</i> and <i>Pseudomonas aeruginosa</i> were the most frequently isolated pathogens, with high resistance rates. Acute kidney injury occurred in 25.8% of patients and was associated with higher APACHE II, SOFA, and SOFA-2 scores. <b>Conclusions</b>: Severe respiratory infections in critically ill patients were predominantly caused by Gram-negative, frequently drug-resistant pathogens and were associated with high disease severity and poor outcomes. These findings provide insight into the local epidemiology and antimicrobial resistance patterns of severe respiratory infections in critically ill patients.