Prevalence of Resistance Genes GyrB, in Particular, Indicates Widespread Resistance to Carbapenem in Acinetobacter baumannii

Background: Acinetobacter baumannii is a major cause of hospital-acquired infections, notable for its ability to acquire resistance to multiple antibiotic classes. Carbapenem resistance in A. baumannii is a global concern, significantly limiting therapeutic options. Among resistance mechanisms, mutations in chromosomal genes such as gyrB, which encodes the B subunit of DNA gyrase, have been increasingly associated with reduced susceptibility to fluoroquinolones and possible co-resistance to carbapenems. Objective: This study aimed to assess the prevalence of resistance-associated genes, with a particular focus on gyrB, in clinical isolates of A. baumannii and to evaluate their association with carbapenem resistance patterns. Methods: A total of 50 clinical isolates of A. baumannii were collected from urinary tract infection (UTI) cases. Antimicrobial susceptibility testing was performed using disk diffusion and broth microdilution methods, following CLSI guidelines. PCR was applied for the detection of the gyrB gene and sequencing of gyrB-positive isolates was carried out to identify point mutations associated with resistance. Results: Among the isolates, 86.7% exhibited resistance to imipenem and meropenem. The gyrB gene was detected in 92% of isolates and sequence analysis revealed mutations linked to quinolone resistance and potential multidrug resistance. Coexistence of gyrB with other resistance mechanisms was common. A strong correlation was observed between gyrB-positive strains and elevated MICs for both carbapenems and fluoroquinolones (p<0.01). Conclusion: The high prevalence of gyrB and its associated mutations among A. baumannii isolates underscores its potential role in mediating broad-spectrum antimicrobial resistance, including resistance to carbapenems. These findings highlight the urgent need for molecular surveillance and the development of novel therapeutic strategies to combat resistant A. baumannii strains.