Acquisition of plasmids conferring carbapenem and aminoglycoside resistance and loss of surface-exposed macromolecule structures as strategies for the adaptation of Acinetobacter baumannii CC104O/CC15P strains to the clinical setting

PAGANINI, JULIAN; SALCEDO, SUZANA P.; CAMERANESI, MARÍA M.; MORAN-BARRIO, JORGELINA; REPIZO, GUILLERMO D.; LIMANSKY, ADRIANA S.; VIALE, ALEJANDRO M.

Microbial Genomics

Microbiology Society

Lugar: Londres; Año: 2020

Acinetobacter baumannii (Aba) is an emerging opportunistic pathogen associated to nosocomial infections. The rapid increase in multidrugresistance (MDR) among Aba strains underscores the urgency of understanding how this pathogen evolves in the clinical environment. Weconducted here a whole-genomesequence comparative analysis of three phylogenetically and epidemiologically related MDR Aba strains fromArgentinean hospitals, assigned to the CC104O/CC15P clonal complex. While the Ab244 strain was carbapenem-susceptible,Ab242 and Ab825,isolated after the introduction of carbapenem therapy, displayed resistance to these last resource β-lactams. We found a high chromosomalsynteny among the three strains, but significant differences at their accessory genomes. Most importantly, carbapenem resistance in Ab242and Ab825 was attributed to the acquisition of a Rep_3 family plasmid carrying a blaOXA-58 gene. Other differences involved a genomic island carryingresistance to toxic compounds and a Tn10 element exclusive to Ab244 and Ab825, respectively. Also remarkably, 44 insertion sequences(ISs) were uncovered in Ab825, in contrast with the 14 and 11 detected in Ab242 and Ab244, respectively. Moreover, Ab825 showed a higherkilling capacity as compared to the other two strains in the Galleria mellonella infection model. A search for virulence and persistence determinantsindicated the loss or IS-mediatedinterruption of genes encoding many surface-exposedmacromolecules in Ab825, suggesting thatthese events are responsible for its higher relative virulence. The comparative genomic analyses of the CC104O/CC15P strains conducted hererevealed the contribution of acquired mobile genetic elements such as ISs and plasmids to the adaptation of A. baumannii to the clinical setting.