Galleria mellonella as an infection model for the multi-host pathogen Streptococcus agalactiae reflects hypervirulence of ST283

Streptococcus agalactiae, or group B streptococcus (GBS), infects diverse hosts including humans, economically important livestock and fishes. In the context of human health, GBS is a major cause of neonatal infections and an emerging cause of invasive disease in adults. Here we show that GBS is able to establish a systemic infection in G. mellonella larvae that is associated with extensive bacterial replication and dose dependent larval survival. This infection model is suitable for use with GBS isolates from both homeothermic and poikilothermic hosts and a hypervirulent sequence type (ST) associated with invasive human disease, ST283, shows increased virulence in this model, indicating it may be useful in studying GBS virulence determinants. In addition, we demonstrate that larval survival can be afforded by antibiotic treatment and so the model may also be useful in the development of novel anti-GBS strategies. The use of G. mellonella in GBS research has the potential to provide a low cost infection model that could reduce the number of vertebrates used in the study of GBS infection.