Background: Emerging of tigecycline resistant Acinetobacter baumannii (A. baumannii)
is a critical global health problem as tigecycline is considered the last-line antibiotic for
treatment of carbapenem resistant A. baumannii infections. Overexpression of efflux
pumps is a leading mechanism of antibiotic resistance in A. baumannii. Objectives:
Detection of the presence of three efflux pump genes; adeB, adeJ and adeG and
determination of their expression level in Tigecycline Resistant A. baumannii collected
from Benha University Hospital. Methodology: Thirty A. baumannii strains were
collected and tested for antibiotic susceptibility. Presence of adeB, adeJ and adeG genes
was detected by conventional PCR and their expression levels were assessed by RT-PCR.
Results: Tigecycline susceptibility showed 60% (18/30) resistance and 40% (12/30)
sensitivity. In tigecycline resistant strains, adeB gene was identified in 13/18 (72.2%)
and adeJ gene in 12/18 (66.7%) with statistically significant association (P= 0.023). In
tigecycline sensitive isolates adeB and adeJ genes were identified in 7/12 (58.3%) and
2/12 (16.7%) strains respectively. The adeG gene was not identified in any of the
isolated strains. Combined adeB and adeJ genes were identified in 50% of tigecycline
resistant isolates and only in 8.3% of (tigecycline sensitive) isolates with statistical
significance difference (P= 0.018). Comparing adeB and adeJ gene expression revealed
that transcription level was increased significantly and associated with tigecycline
resistance. Conclusion: This study revealed wide spread of tigecycline resistant A.
baumannii strains in Benha University Hospital and elucidated the significant role of
(adeB and adeJ) genes in their emergence.