Pangenomics of high-risk international clones in Acinetobacter baumannii identifies distinctive virulence and antimicrobial resistance profiles.

The bacterial pathogen Acinetobacter baumannii is an opportunistic and nosocomial causative agent of multidrug resistant infections worldwide. The present study conducted comparative genomic analyses to identify relevant pathogenicity traits in A. baumannii strains from diverse clinical samples and geographical regions in Mexico. Pangenome analysis clustered the strains into four phylogenomic clades, comprising various international clones. Clades I and II strains, predominantly from blood and respiratory infections in the Central region, were significantly associated with the Latin American IC5 clone (P = 0.0002), whereas clade III strains, primarily from diverse samples in the Northwestern region, were significantly associated with the European IC2 clone (P = 0.0030). Virulence determinants implicated in adhesion (ompA, omp38), biofilm formation (pgaA-D, csuA/BABCDE), motility (pil, fim), regulatory systems (bfmRS, barAB, abaR/abaI), iron acquisition (bas, bau), and efflux pump-delivery systems (adeFGH) were identified among the A. baumannii strains, representing all clades and geographical regions. Analysis of intrinsic and acquired antimicrobial resistance revealed that clades I and II strains were significantly correlated with resistance to β-lactamases (blaADC-6, blaOXA-239, blaOXA-65), sulfonamides (sul2), and chloramphenicol (cmlB1) (P = 0.0001). Interestingly, clade III strains, predominantly from the agricultural Northwestern region, exhibited a significant association of broader resistance genes against aminoglycosides (aac(6')-Ib', aph(3')-Ia, armA, aadA), β-lactamases (blaTEM-4, blaADC-25, blaOXA-66), sulfonamides (sul1), tetracyclines (tetA), and macrolides (mphD, msrE) (P = 0.0001). Subsequent characterization of mobile genetic elements indicated genetic plasticity and potential transfer of antimicrobial resistance. Collectively, this fundamental information would enable the improvement of epidemiological surveillance and intervention strategies for A. baumannii.