No / Streptococcus agalactiae is a major neonatal pathogen. Disease progression is characterised by bacterial adaptation from commensal maternal vaginal colonisation to environments associated with neonatal disease, including exposure to blood. To explore this adaptation in vitro, we have used proteomics to identify proteins differentially expressed following growth on Todd Hewitt agar in the presence or absence of 10% v/v human serum. Twelve differentially expressed proteins were identified. Notably, the C protein β antigen and arginine deiminase proteins were upregulated following growth in the presence of human serum, consistent with previous studies implicating these two proteins in the pathogenesis of S. agalactiae disease.

No / Streptococcus agalactiae is a major neonatal pathogen that is able to adapt to a variety of host environments, including both rectal and vaginal maternal carriage, growth in amniotic fluid and at various neonatal body sites. As such it is important to elucidate the patterns of protein expression that are associated with S. agalactiae growth under these different in vivo conditions. To this end, we have grown S. agalactiae strain A909 under in vitro conditions reflecting those associated with maternal vaginal carriage (low pH, low oxygen, nutrient stress) and those associated with exposure to body fluids during invasive disease (neutral pH, aeration, nutrient sufficient). The protein profiles of bacterial cells grown under each of these conditions were compared using a proteome approach. A total of 76 proteins were reproducibly identified 16 of which were shown to be differentially expressed. The putative virulence factor C protein β and several proteins linked to resistance to oxidative stress were found to be upregulated under the conditions hypothesised to reflect those associated with foetal exposure to S. agalactiae. Thus, these data add to the currently limited understanding of the molecular basis of S. agalactiae GBS adaptation to different environmental conditions.