Genetic profiling of multidrug-resistant <i>Acinetobacter baumannii</i> from a tertiary care center in Malaysia

Genetic characterization of multidrug-resistant (MDR) <i>Acinetobacter baumannii</i> remains scarce in Malaysia. This study aimed to characterize antibiotic resistance, genomic location, and genetic relatedness among the <i>A. baumannii</i> isolates obtained from a tertiary hospital in Malaysia. A total of 128 MDR <i>A. baumannii</i> 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, <i>bla</i>_OXA-23, <i>bla</i>_OXA-24, <i>bla</i>_ADC, <i>bla</i>_VIM, and <i>bla</i>_IMP, were detected in chromosomal and plasmid DNA using PCR. Insertion sequence IS<i>Aba</i>1/<i>bla</i>_OXA-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 <i>A. baumannii</i> 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 <i>bla</i>_OXA-23, <i>bla</i>_VIM, and <i>bla</i>_ADC were detected in both chromosomal and plasmid DNA. The IS<i>Aba</i>1/<i>bla</i>_OXA-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 <i>bla</i>_OXA-23, indicating an evolutionary adaptation of <i>A. baumannii</i> within the hospital setting.IMPORTANCE<i>Acinetobacter baumannii</i> is a ubiquitous Gram-negative coccobacillus bacterium that is primarily associated with nosocomial infections that can colonize biotic and abiotic surfaces to enhance cell-to-cell adhesion, ensuring the establishment of infections. To date, the spread of multidrug-resistant <i>A. baumannii</i> (MDRAB) has become rampant and a great concern in the hospital setting, as the available antibiotics are insufficient to treat infections. The antibiotic resistance island resides in a mobile element and rapidly evolved. The antibiotic susceptibility data with its resistance mechanisms would contribute to and facilitate the management and infection control caused by MDRAB.