Comparative genomic insight into Acinetobacter baumannii and Acinetobacter nosocomialis: uncovers the functional basis of multidrug resistance and biofilm-related virulence.

Acinetobacter species are opportunistic pathogens that possess both intrinsic and acquired drug resistance, as well as the capacity to develop persistent biofilms. Among them, the most important multidrug-resistant species are Acinetobacter baumannii and Acinetobacter nosocomialis. The in silico comparative genomic study has systematically analyzed these two species with emphasis on antimicrobial resistance genes and virulence factors that promote biofilm formation. Both species contain several biofilm-associated genes, such as ompA, pilE, csuA/b, pgaA-D, and the AdeFGH efflux system, which are important for persistence, colonization, and drug tolerance, along with those involved in lipopolysaccharide biosynthesis and serum resistance. A. baumannii has the fliP and wbpI genes that are species-specific, while mbtH and hemO genes suggest increased iron uptake capabilities to those of A. nosocomialis. The katA gene identification indicates better adaptation to oxidative stress for A. baumannii, while both species have wbjD/wecB associated with capsule formation. A. baumannii displays greater functional diversity based on the subsystem analysis, and that species appears to have additional iron acquisition mechanisms. Analysis of the integrons showed two integrons in A. baumannii, indicating increased genomic plasticity for the insertion and removal of plasmids. Twenty-six essential and potentially druggable proteins were identified as shared by both species through drug-target analysis. Antimicrobial activity and biofilm assays showed minimal inhibition in A. baumanni and A. nosocomialis, confirming resistance. Overall, this comparative genomic study supports future efforts to develop effective therapeutic interventions and provides valuable insights into the virulence and resistance strategies of these pathogens.