Abstract
Acinetobacter radioresistens is an uncommon human pathogen rarely reported to cause bacteremia. Its accurate identification is crucial yet challenging, with implications for antimicrobial stewardship due to its potential to harbor carbapenem resistance genes. We present the case of a 77-year-old male with metastatic lung adenocarcinoma, COPD, and dementia who presented with acute hypoxic respiratory failure and septic shock. Initial empiric antibiotics were vancomycin and cefepime. Gram stain of positive blood cultures revealed Gram-negative coccobacilli. The VERIGENE BC-GN microarray system identified an Acinetobacter species, negative for common resistance markers, which was subsequently confirmed as pan-susceptible Acinetobacter radioresistens by MALDI-TOF mass spectrometry. The patient's antibiotic regimen was de-escalated to intravenous ampicillin-sulbactam, to which he initially responded. His course was later complicated by recurrent respiratory failure, and his family transitioned him to comfort care. He expired shortly after withdrawal of life support. This case underscores the emerging clinical significance of A. radioresistens as an opportunistic pathogen in immunocompromised hosts. It highlights the utility of rapid molecular diagnostics for precise pathogen identification and antimicrobial stewardship, while also illustrating the critical role of confirmatory methods like MALDI-TOF. Vigilance for less common Acinetobacter species is warranted in patients with significant comorbidities.