Identification of Efflux Pumps Genes (adeB, adeJ and adeG ) in Acinetobacter baumannii Resistant to Tigecycline

Background: Acinetobacter baumannii is an opportunistic bacterium commonly associated with multidrug-resistant infections. One of the major therapeutic challenges is tigecycline resistance in clinical isolates. This study aimed to identify the presence of efflux pump genes )adeB, adeJ, and adeG( in tigecycline-resistant A. baumannii, to support efforts in controlling antibiotic resistance. Methods: A cross-sectional study was conducted on 44 hospitalized patients at the Clinical Pathology Department, Zagazig University Hospitals. The presence of adeB, adeJ, and adeG efflux pump genes was assessed, and antimicrobial susceptibility testing was performed. Results: Among the 44 patients, the mean age was 55.3±16.86 years, with 68.2% males. ICU patients represented 68.2%, and median hospital stay was 16 days. Tigecycline resistance was observed in 54.5% of isolates, with resistance also noted for tetracycline (56.8%), ticarcillin/clavulanate (93.2%), piperacillin (95.5%), levofloxacin (93.2%), ceftriaxone (95.5%), cefepime (95.5%), and meropenem(93.2%). Significant risk factors for tigecycline resistance included prior antibiotic use, chronic lung disease, mechanical ventilation, ICU admission, prolonged hospitalization, and the presence of AdeB and combined AdeB+AdeJ efflux pump genes (p<0.05). Tigecycline resistance was significantly associated with decreased susceptibility to tetracycline and minocycline. Multivariate analysis identified AdeB positivity, combined AdeB+AdeJ, prior antibiotic use, ICU admission, mechanical ventilation, and prolonged hospitalization as independent predictors of resistance. Conclusion: Tigecycline-resistant A. baumannii is prevalent among ICU patients, particularly those with prior antibiotic exposure and invasive procedures. Efflux pump genes, especially AdeB and AdeB+AdeJ, play a central role in mediating resistance.