Genomic characterization and comparative analysis of Leptospira interrogans serogroup Australis isolated from swine

The Leptospira interrogans serogroup Australis is traditionally described as pathogenic for swine although animals usually present low serologic response and mild clinical signs. The first isolation of a Leptospira interrogans serogroup Australis strain from swine, in Brazil, was recently described. Herein we present the genomic characterization of this strain (SU5) and further comparison with the Leptospira serovars reference genomes available in the GenBank database. The SU5 strain was characterized with sequence types previously described in a serogroup Australis isolated from human and presented a new ST98 that is thus far exclusively of the Brazilian porcine L. interrogans serogroup Australis. Even though the SU5 strain presented higher similarity with the American porcine serogroup Australis strain PigK151, as expected, it also presented sequences blocks in both chromosomes which are absent in the genomes of the studied Leptospira serovars. These regions are flanked by insertion sequences and transposases genes, suggesting the existence of inter- and intra-serogroup genomic variability due to mobile elements transferring. This genomic plasticity has already been demonstrated for pathogenic Leptospira species; nevertheless, there is still a limited understanding of the relationship between genome organization and content and the divergence of Leptospira serogroups and serovars that needs to be further elucidated.