Evidence of a novel sublineage of Streptococcus agalactiae in elephants from zoo populations in Germany

Abstract

Streptococcus agalactiae research primarily centres on investigating human and bovine infections, although this pathogen also can be carried and cause infections in a wider range of animal species. Moreover, infections with S. agalactiae are posing significant health implications, and recent studies furthermore are highlighting a potential zoonotic risk. Despite the relatively frequent isolation of S. agalactiae from elephants, only a few reports document infections in wild and zoo populations. We performed a comparative genomic analysis of 24 elephant isolates from three different zoos in Germany to achieve a comprehensive characterization. Elephant isolates showed pronounced phylogenetic divergence from isolates of other host species, while also forming clusters based on zoo of origin and their genotypes (MLST profiles). Capsular serotypes could not be predicted for the majority of the isolates (n=20/24). Several genes, exclusively associated with the elephant host, may underlie the pathogen’s capacity to improve its survival and virulence across varied ecological niches. This study not only deepens our understanding of S. agalactiae across diverse species and environments but also represents the first whole-genome sequencing characterization of S. agalactiae isolates from elephants, helping to expand our knowledge about infections in animals.