| Summary: | Genetic characterization of multidrug-resistant (MDR) Acinetobacter baumannii remains scarce in Malaysia. This study aimed to characterize antibiotic resistance, genomic location, and genetic relatedness among the A. baumannii isolates obtained from a tertiary hospital in Malaysia. A total of 128 MDR A. baumannii isolates were collected from patients admitted to various wards (intensive care unit [ICU], neonatal intensive care unit, coronary care unit, high dependency ward [HDW], and general wards). The isolates were identified by Vitek 2 and PCR amplification of the 16S rRNA gene followed by sequencing. The isolates were tested against imipenem, ceftazidime, amikacin, gentamicin, ampicillin, and ciprofloxacin using disk diffusion, Epsilometer test, and broth microdilution. The antibiotic resistance genes, blaOXA-23, blaOXA-24, blaADC, blaVIM, and blaIMP, were detected in chromosomal and plasmid DNA using PCR. Insertion sequence ISAba1/blaOXA-23 gene was detected on chromosomal DNA only. Isolates with different antibiotic susceptibility patterns and PCR profiles were subjected to multi-locus sequence typing. MDR A. baumannii was predominantly found in HDW (39.84%), general wards (29.69%), and ICU (28.13%). All isolates conferred resistance to carbapenem and more than 90% resistance to the remaining antibiotics. The antibiotic resistance genes blaOXA-23, blaVIM, and blaADC were detected in both chromosomal and plasmid DNA. The ISAba1/blaOXA-23 gene was detected in 99.22% of the isolates. Four sequence types (STs) were distinguished: ST2 (76.67%), ST164 (10%), ST642 (10%), and ST643 (3.33%). ST164 and ST642 were unique and represent a significant finding in Malaysia’s surveillance data. These STs are associated with acquired blaOXA-23, indicating an evolutionary adaptation of A. baumannii within the hospital setting. Copyright © 2024 Shahari et al.
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