New insights regarding Acinetobacter genomic island-related elements.

The objective of this study was to mobilise the Acinetobacter genomic island 1-A (AGI1-A) from Enterobacter hormaechei EclCSP2185 (E. cloacae complex) and to search for the distribution and structure of AGI1-related elements in the NCBI database. AGI1-A was transferred to Escherichia coli. Analysis of the attachment (att) sites could locate the possible recombination crossover in the att sequences at position 10-11 (GG) in the last 18 bp of trmE. In silico detection of AGI backbones in the WGS database identified AGI variants in Salmonella enterica (83 strains), Vibrio cholerae (33), E. hormaechei (12), Acinetobacter baumannii (2), most belonging to prevalent clones (ST40, ST69, ST114 and ST25, respectively), but also in E. coli (1) and Klebsiella pneumoniae (1). Two groups of backbone were identified: one similar to AGI1, the other with a short segment from a Shewanella element upstream of ORF A022. The MDR regions were inserted by transposition at the res site in four different positions ATAGG (A. baumannii), CATAG (S. enterica and V. cholerae), TAGGT (S. enterica and K. pneumoniae) and TGCAC (S. enterica) representing four different lineages. In some V. cholerae, E. hormaechei and E. coli, deletion events occurred that eliminated part of the backbone at the left junction. Analysis of the right junction identified a fifth lineage in V. cholerae and E. hormaechei (CCATA). In conclusion, based on the position of the MDR region, AGI-related elements belonged to five groups of closely related genomic islands (AGI1-AGI5), with differences in backbones that evolved independently over time.