Community-acquired Acinetobacter baumannii pneumonia in Southern Vietnam: A retrospective cohort study

Acinetobacter baumannii has traditionally been considered a nosocomial pathogen, but cases of community-acquired A. baumannii pneumonia have increasingly been reported in tropical Asia, including Vietnam. Data on its clinical characteristics, antimicrobial resistance, and patient outcomes remain limited. This study aimed to describe the clinical profile, resistance patterns, and outcomes of community-acquired A. baumannii pneumonia in southern Vietnam. We performed a single-center retrospective cohort study at Nhan Dan Gia Dinh Hospital, a 1500-bed tertiary center in Ho Chi Minh City (January 2021-December 2023). Adults (≥18 years) with community-acquired pneumonia and a positive sputum, endotracheal aspirate, or blood culture for A. baumannii obtained within 48 hours of admission were included. Patients with cultures >48 hours after admission, hospitalization in the prior 90 days, residence in/transfer from another facility ≥48 hours preadmission, polymicrobial cultures, or incomplete records were excluded. Thirty-one patients were identified (median age 69.0 years (interquartile range 64.0-84.0); 83.9% male; 83.9% current/former smokers). No clear seasonal predominance was observed within the study window after month-level normalization. On admission, 87.1% had hypoxemia (peripheral oxygen saturation<90%) and nearly half (45.2%) were severe community-acquired pneumonia. Antibiotic escalation was required in 61.3% after a median of 4 days (interquartile range 3-5). Resistance was approximately 69%-83% across the routinely tested β-lactams and fluoroquinolones, whereas aminoglycosides showed comparatively higher in vitro activity than the other tested antibiotic classes but susceptibility remained suboptimal (amikacin 50%, tobramycin 46%, gentamicin 36%). Initial empiric therapy was active against the index isolate in 4/25 patients (16.0%) with available susceptibility results. In-hospital mortality was 13/31 (41.9%). Community-acquired A. baumannii pneumonia is associated with severe disease, extensive antimicrobial resistance, frequent empiric treatment mismatch, and high mortality. In resource-constrained settings, limited therapeutic options highlight the importance of early microbiological diagnosis, comprehensive susceptibility testing, and locally informed treatment strategies.