Streptococcus agalactiae

Group B Streptococcus (GBS, Streptococcus agalactiae) is a common cause of sepsis and meningitis in newborns and is an important cause of invasive disease in both pregnant and nonpregnant adults. Infants who contract the disease shortly after birth suffer 10-20% mortality rates, and survivors may suffer permanent complications.  The pathogenesis and transmission of GBS infection is not completely understood. However, up to 40% of healthy adults are colonized with GBS. Prevention efforts such as vaccination are needed in order to protect pregnant and nonpregnant adults from GBS disease.   Identifying virulence factors involved in the pathogenesis of GBS is important both for the development of effective vaccines and identification of alternative prevention strategies.  Part of our research into GBS involves the examination of a group of hypervariable genes, which may potentially play a role in virulence of this organism.   

Additionally, GBS was originally identified as a cause of bovine mastitis, and this disease is believed to involve biofilm formation.  To date, however, only one study has been conducted examining the effect of growth of GBS in a biofilm.  In this study, it was found that GBS that had been grown in a biofilm were significantly more resistant to exposure to an entire panel of antibiotics than planktonic (liquid culture-grown) bacteria grown for a similar length of time.  However, only one strain of GBS was tested (a strain isolated from a case of bovine mastitis), so it is not currently known whether this is a property of GBS as a species, or unique to that particular strain.  Investigators in that study also did not test resistance to two common antibiotics used in humans:  erythromycin and clindamycin.  GBS has been shown to often exhibit resistance to these antibiotics, while remaining generally sensitive to penicillin in planktonic cultures.  Additional studies in our lab seek to examine antibiotic resistance and virulence gene expression in GBS that have been grown in a biofilm versus planktonic bacteria.