Expression of Genes Associated with Efflux Pump and Porins in Acinetobacter baumannii Isolates Recovered from Different Clinical Specimens

Abstract Background: Efflux pumps are crucial bacterial defense mechanisms that reduce antibiotic susceptibility by expelling antibiotics from cells. In Acinetobacter baumannii , this significantly contributes to multidrug resistance. In addition, porin alterations, essential for carbapenem uptake, further enhance resistance by limiting antibiotic entry. This study examines these mechanisms to improve treatment strategies. Methods: A cross-sectional descriptive study was conducted on 300 clinical samples collected from Hilla Teaching Hospitals between January and June 2024. Samples were obtained from wounds (40%), burns (40%), blood (12%), and urine (8%). Specimens were collected from burn wards and the intensive care unit. Patients ranged in age from 10 to 40 years. Specimens included 200 females and 100 males. Specimens were collected during hospitalization. Bacteria were cultured and identified by Gram stain and biochemical tests and confirmed to be A. baumannii (8.33%) using the Vitek-2 system. Antibiotic susceptibility testing was performed against 16 antibiotics. Molecular detection of efflux pump genes (adeB and adeJ) was performed using polymerase chain reaction (PCR), and gene expression was measured by reverse transcriptase PCR. Results: A. baumannii isolates showed high resistance to antibiotics, especially β-lactams, carbapenems, and aminoglycosides, whereas colistin remained effective. All isolates carried the adeB gene, whereas adeJ was not detected. Overexpression of OperD (80%) and adeB (44%) was observed, along with consistent downregulation of the CarO gene (100%). Conclusion: A. baumannii isolates exhibited significant antibiotic resistance, particularly to β-lactams, carbapenems, and aminoglycosides, complicating infection treatment. Colistin remained the only effective option. Molecular analysis confirmed the presence of the adeB gene in all isolates, with no detection of adeJ. Overexpression of OperD (80%) and adeB (44%) emphasized efflux pumps’ role in resistance, whereas CarO gene downregulation (100%) likely contributed to carbapenem resistance. These results highlight the urgent need for continuous monitoring and new treatment approaches for multidrug-resistant A. baumannii .