Abstract
Acinetobacter baumannii is a non-fermentative Gram-negative bacillus known for its environmental persistence, rapid acquisition of multidrug resistance (MDR), and high outbreak potential. The 2024 World Health Organization priority pathogen list places it in the highest "Critical" tier. This review summarizes definitions, resistance mechanisms, epidemiology in Japan and abroad, diagnostic approaches, infection control, and current or emerging therapies. Carbapenem resistance is largely mediated by OXA-type carbapenemases, often together with additional mechanisms. While isolates in Japan still show comparatively high susceptibility to key agents, many Asia-Pacific and Latin American settings report substantially higher resistance. Phenotypic and molecular diagnostic tools remain essential for outbreak control. Despite the availability of several established and novel agents, no universally accepted regimen exists, and combination therapy is often necessary. This observed gap in resistance levels may reflect variation in surveillance intensity, infection control policies, and antimicrobial stewardship. Appreciating these contextual differences can inform countries that are beginning to face increasing MDR A. baumannii burdens and support the design of locally applicable preparedness strategies.