Mixed Pneumonia with Pulmonary Embolism and Multiple Pathogens Detected in Bronchoalveolar Lavage Fluid: A Case Report.

Severe community-acquired pneumonia may involve mixed pathogens and concurrent vascular complications. A 72-year-old man presented with fever, nonproductive cough, vomiting, hypoxemia, markedly elevated inflammatory markers, and an elevated D-dimer concentration. Chest computed tomography showed left lower-lobe consolidation and pleural effusion. Computed tomography pulmonary angiography, obtained because of hypoxemia and suspected pulmonary embolism, showed a filling defect in a right upper-lobe pulmonary artery. The patient received antimicrobial therapy prior to bronchoalveolar lavage (BAL). Bronchoscopy was performed in the bronchopulmonary segment corresponding to the radiographic lesion, and approximately 10 mL of bronchoalveolar lavage fluid (BALF) was recovered aseptically for microbiological and cytological testing. An aliquot of at least 3 mL was allocated to a multiplex pathogen-targeted sequencing assay, which detected Chlamydia psittaci, influenza A H3N2, Streptococcus pneumoniae, and additional conditionally pathogenic or commensal organisms. The three principal detections were interpreted in conjunction with the clinical presentation, imaging, inflammatory markers, BALF cytology, conventional testing, and treatment response. The patient improved during antimicrobial and anticoagulant treatment and was discharged on December 3, 2025. At the documented outpatient follow-up on December 17, rivaroxaban was continued for approximately one further month. This case highlights the adjunctive value and interpretive limitations of targeted sequencing in a treated patient. The serial imaging and invasive sampling reflected case-specific decisions and should not be interpreted as a routine protocol for pneumonia.