Unusual finding of the human-adapted hypervirulent serotype III/ST17 clone in a historical bovine Group B Streptococcus isolate from Brazil.

Group B Streptococcus (GBS) is a leading cause of human neonatal infections and bovine mastitis. We report here the unusual finding of the human-adapted hypervirulent serotype III/ST17 clone in a bovine GBS isolated in 1987 in Brazil. This isolate shared several phenotypic and genotypic characteristics with serotype III/ST17 strains obtained from human sources, including PFGE pattern, pilus genes, lactose fermentation, DNase activity, and antimicrobial susceptibility profile, highlighting the importance of continued tracking of GBS in the One Health scope. The study brings new evidence for the potential interspecies transmission and sheds new light into evolution aspects of the pathogen Group B Streptococcus (GBS) by reporting the occurrence of an ancient bovine GBS isolate belonging to a variant currently known to be exclusively found in human hosts.