CONICET | Buscador de Institutos y Recursos Humanos

Acinetobacter baumannii was recently recognized as a successful nosocomial pathogen, with an increasing morbidity and mortality due the rise in multi- and pan-drug resistant strains (Perez et al. 2007). Its clinical importance led to extensive studies on different aspects of the biology and pathogenesis (McConnell et al. 2013). To this date the genomes of 19 A. baumannii strains have been sequenced and those of more than 200 other isolates are at the draft stage in GenBank. Genome comparisons showed high variability, which could be the result of the combination of natural competency and the presence of very active recombination system(s) (Ramirez et al. 2011; Smith et al. 2007). These processes could also explain the unusual tendency of A. baumannii to acquire multiple antibiotic resistance determinants and to survive in the hospital environment (Hornsey et al. 2011; Sahl et al. 2013; Snitkin et al. 2011; Tan et al. 2013). A recent study showed that three strains belonging to the international clonal lineage 2 (ICL2) have an elevated number of SNPs when compared to the ICL2 prototype ACICU strain. Most SNPs were preferentially located in specific ?recombinant regions?, which was interpreted as the product of homologous recombination-mediated DNA swapping (Snitkin et al. 2011) Conversely, another comparative study between two A. baumannii strains, one of them an extreme-drug resistant and the other a pan-drug-resistant, showed only 61 SNPs between them (Tan et al. 2013). However, despite the relatively small number of SNPs observed between the two strains, the authors concluded that the changes are indicative of fast evolution because the mutations occurred within a 1-month period (Tan et al. 2013). We recently initiated the characterization of the first laboratory confirmed naturally competent A. baumannii strain, A118, an isolate that unlike other clinical isolates is susceptible to numerous antibiotics (Ramirez et al. 2010; Ramirez et al. 2011). In this report we describe a comparative study to gain insights into the nature and extent of the genomic differences found in Ab A118 strain when its genome is compared with those of strains ATCC 17978, AYE, and ACICU.