Streptococcus agalactiae infection in zebrafish larvae

Streptococcus agalactiae (Group B Streptococcus, CBS) is an encapsulated, Gram-positive bacterium that is a leading cause of neonatal pneumonia, sepsis and meningitis, and an emerging aquaculture pathogen. The zebrafish (Danio rerio) is a genetically tractable model vertebrate that has been used to analyze the pathogenesis of both aquatic and human bacterial pathogens. We have developed a larval zebrafish model of CBS infection to study bacterial and host factors that contribute to disease progression. CBS infection resulted in dose dependent larval death, and CBS serotype III, ST-17 strain was observed as the most virulent. Virulence was dependent on the presence of the CBS capsule, surface anchored lipoteichoic acid (LTA) and toxin production, as infection with CBS mutants lacking these factors resulted in little to no mortality. Additionally, interleukin-1 beta (il1b) and CXCL-8 (cxcl8a) were significantly induced following CBS infection compared to controls. We also visualized CBS outside the brain vasculature, suggesting CBS penetration into the brain during the course of infection. Our data demonstrate that zebrafish larvae are a valuable model organism to study GBS pathogenesis. (C) 2015 Elsevier Ltd. All rights reserved.