Genomic and phenotypic analysis of multidrug-resistant Acinetobacter baumannii focusing on efflux pump activity and biofilm-associated genes

Background Acinetobacter baumannii evolved as a critical pathogen of global concern due to its persistence and pathogenicity. To elucidate the underlying resistance mechanism, the role of efflux pumps and biofilm-associated genes was investigated. Furthermore, the genes that serve as potential targets or biomarkers were identified, offering valuable insights for the development of novel antimicrobial agents and optimization of antibiotic-based therapies.
Materials and methods Nineteen A. baumannii isolates were analysed for antibiotic resistance, efflux pump functionality,and biofilm formation. The ABS2 isolate underwent whole-genome sequencing (GenBank: JBJJNX000000000.1) to characterize resistance and virulence determinants, including the oxidative stress repair gene yajL, using the FunRich enrichment tool.
Results All isolates exhibited multidrug resistance, showing 100% resistance to ceftazidime and imipenem, with functional
efflux pumps detected in every isolate using cartwheel method. Biofilm formation, assessed by the tissue culture plate method, was observed in 89% of isolates. PCR analysis revealed high prevalence of resistance genes bla OXA-51 (100%),Intl-1 (79%) and Intl-2 (15%). Efflux pump genes adeA (89%), adeB (100%), and adeC (63%) were present, while biofilm-associated genes cusE, ompA, pgaA, and abaI were also detected. Whole-genome and enrichment analyses of ABS2 revealed a diverse resistome and virulome contributing to oxidative stress resistance and immune evasion.
Conclusion The study highlights the high prevalence of biofilm formation and efflux pump-mediated resistance among A.baumannii isolates. Genomic insights into the ABS2 isolate emphasize its adaptability to hostile environments and
potential to cause persistent infections, underscoring the global health threat posed by multidrug-resistant, biofilm-forming A.baumannii.
Keywords Acinetobacter baumannii · Multidrug resistance · AdeABC · Genome sequencing · Enrichment analysis