Pneumonia Pathogens' Virulence Factors, Patient Inflammatory Markers, and Their Associations With Outcomes

The study will assess pneumonia symptoms based on physical examination and additional data (radiological or laboratory tests), supported by prognostic scales such as the Pneumonia Severity Index (PSI), CURB65 (Annexes No. 7 and 8), in combination with biomarkers and inflammatory cytokines. This approach aims to improve decision-making and predict poor outcomes. In the process of lower respiratory tract infections, the level of procalcitonin (PCT) is intended to guide both the initiation and duration of antibiotic therapy. Additionally, treatment may vary depending on the initial levels of inflammatory biomarkers. Under the influence of pro-inflammatory cytokines (IL-6, G-CSF), CD64 can increase more than tenfold within 4-6 hours. Normally, CD64 expression is low, but it significantly increases within hours when activated by infection. Once the activation subsides, CD64 expression returns to baseline levels within a few days. The summarized data will show correlations between pathogens, their virulence factors, the patient's immune response, and disease outcomes.

Microbiological testing will be conducted when results could influence antimicrobial therapy selection. Sputum microscopy is planned before prescribing antibacterial treatment. Only good-quality sputum samples will be considered for accurate diagnosis. If microscopy reveals poor-quality sputum, further testing will not be pursued. Invasive methods for determining the etiology are intended to be used only when required by pneumonia diagnostic and treatment protocols. The study is planned to be conducted exclusively in specialized hospital units that ensure patient safety. Bronchoscopy, including bronchoalveolar lavage (BAL), is indicated in cases of severe pneumonia and at least one of the following conditions:

• inability to expectorate sputum;
• absence of predominant potential pathogens in sputum culture;
• inadequate response to treatment based on susceptibility of the isolated pathogen;
• isolation of multiple types of Gram-negative rods or fungi in sputum culture;
• suspected superinfection.

In all cases of pneumonia diagnosis, chest X-rays (anteroposterior and/or lateral views) are planned. Infiltrates located in the 2nd, 6th, 9th, and 10th segments may not be visible on the anteroposterior view alone. On the first day of illness, only local changes in the lung pattern-caused by hyperemia, perivascular and peribronchial edema, and infiltration-may be seen. Therefore, chest radiographic examination is planned to be repeated.

Inclusion criteria

• Age ≥18 years;
• Diagnosed with community-acquired or hospital-acquired pneumonia;
• Provides written informed consent.

Exclusion criteria

• Age under 18;
• Inability to provide informed consent;
• Patients with autoimmune diseases;
• Patients with chronic lung diseases such as cystic fibrosis or COPD;
• Contraindications to venipuncture.