Integrative mobilizable elements belonging to the SGI1-H, -K, and -L genomic island 1 (SGI1) variant groups are distinguished by the presence of an alteration in the backbone (IS replaces 2.8 kb of the backbone extending from within [S005] to within S009). Members of this SGI1-HKL group have been found in serovars and in Two novel variants from this group, designated SGI1-LK1 and SGI1-LK2, were found in the draft genomes of antibiotic-resistant isolates from two French hospitals. Both variants can be derived from SGI1-GUE, a configuration found previously in another isolate from France. SGI1-LK1 could arise via an IS-mediated inversion in the complex class 1 integron that duplicated the IS element and the target site in IS SGI1-LK1 also has a larger 8.59-kb backbone deletion extending from to within S013 and removing and However, SGI1-LK1 was mobilized by an IncC plasmid. SGI1-LK2 can be derived from a hypothetical progenitor, SGI1-LK0, that is related to SGI1-GUE but lacks the gene and one copy of IS The integron of SGI1-LK2 could arise via deletion of DNA adjacent to an IS and a deletion occurring via homologous recombination between duplicated copies of part of the integron 3'-conserved segment. SGI1-K can also be derived from SGI1-LK0. This would involve an IS-mediated deletion and an inversion via homologous recombination of a segment between inversely oriented ISs. Similar events can explain the configuration of the integrons in other SGI1-LK variants. Members of the SGI1-HKL subgroup of SGI1-type integrative mobilizable elements have a characteristic alteration in their backbone. They are widely distributed among multiply antibiotic-resistant serovars and isolates. The SGI1-K type, found in the globally disseminated multiply antibiotic-resistant serovar Kentucky clone ST198 (sequence type 198), and various configurations in the original SGI1-LK group, found in other multiresistant serovars and isolates, have complex and highly plastic resistance regions due to the presence of IS However, how these complex forms arose and the relationships between them had not been analyzed. Here, a hypothetical progenitor, SGI1-LK0, that can be formed from the simpler SGI1-H is proposed, and the pathways to the formation of new variants, SGI1-LK1 and SGI1-LK2, found in and other reported configurations via homologous recombination and IS-mediated events are proposed. This led to a better understanding of the evolution of the SGI1-HKL group.