Epidemiological Characteristics and Antimicrobial Resistance of Extensively Drug-Resistant Acinetobacter baumannii in ICU Wards

Acinetobacter baumannii is a significant nosocomial pathogen, particularly problematic due to its extensive drug resistance. This study investigates 56 extensively drug-resistant A. baumannii (XDRAB) strains collected from various ICU wards at Jinhua Central Hospital, Zhejiang Province, China. Strains were isolated from diverse clinical samples, including sputum, blood, cerebrospinal fluid, and wound secretions. Identification was confirmed via MALDI-TOF mass spectrometry, and antibiotic susceptibility testing was conducted using the VITEK 2 Compact system, E-test, and Kirby-Bauer methods. All strains were susceptible to polymyxin, with four showing intermediate susceptibility to tigecycline, while resistance rates to other antibiotics were 100%. Molecular typing through Pulsed-Field Gel Electrophoresis (PFGE) classified the strains into 10 types, with the dominant type (G) primarily found in ICU3, indicating a potential clonal outbreak. Whole-genome sequencing (WGS) and multi-locus sequence typing (MLST) identified ST208 as the predominant sequence type. Resistance gene screening revealed the presence of blaOXA-23, blaTEM-1D, and aminoglycoside resistance genes in most strains. Phylogenetic analysis confirmed the clonal transmission of ST208 strains across the hospital, with a high degree of genomic similarity among the isolates. These findings highlight the importance of continuous monitoring and effective infection control measures to prevent the spread of XDRAB in healthcare settings.