Case Report: Rare Multidrug-Resistant Enterobacter Cloacae Complicated by Invasive Pulmonary Aspergillosis in an Elderly Patient with Advanced Lung Adenocarcinoma Treated with Osimertinib.

Osimertinib, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), is the standard treatment for EGFR-mutated advanced non-small cell lung cancer (NSCLC). We report a rare case of multidrug-resistant (MDR) Enterobacter cloacae pneumonia complicated by invasive pulmonary aspergillosis (IPA) in a 75-year-old male with lung adenocarcinoma who had been receiving osimertinib for 8 months. Prompt susceptibility-guided therapy with polymyxin B plus tigecycline (for MDR bacteria) and voriconazole (for aspergillosis) achieved complete resolution, highlighting the importance of rapid microbiological diagnosis and targeted antimicrobials in this vulnerable population.