Group_B_Streptococcus_from_maternal_carriage_in_Netherlands

Group B Streptococcus (GBS), also known as Streptococcus agalactiae, is a leading cause of neonatal sepsis and meningitis. It is estimated that around 20% of pregnant women carry GBS asymptomatically. Intrapartum GBS transmission from a colonized mother can lead to colonisation in a neonate, which in turn can result in invasive disease. Implementation of disease prevention guidelines recommending intrapartum antibiotic prophylaxis (IAP) has been shown to reduce the incidence of the disease in newborn babies. However, in some countries such as the Netherlands and the UK, the opposite outcome has been observed, with a steady rise in disease incidence over time. Improved IAP guidelines or new prevention strategies are urgently needed. This can be supported by a better understanding of GBS genetic diversity and genetic association with disease. We previously performed WGS analysis of a nationwide collection of 1345 invasive GBS from infections in infants aged 0 – 89 days that occurred in the Netherlands between 1987 and 2016. We established a high level of genetic discrimination between isolates and found a correlation between the increase in disease incidence over time and expansion of specific clonal groups of GBS. However, as we were limited to the analysis of invasive isolates only, it remains unclear if these expanding clones increased in prevalence only among invasive isolates, or if they are also common among carriage isolates. To address this, we wish to perform a WGS analysis on a collection of GBS isolates from healthy maternal carriage in the Netherlands, to compare the population genetics of the invasive and colonising GBS. A total of 500 GBS strains from two GBS carriage studies, NOGBS 2 (n=50) & NOGBS 3 (n=450) have been collected and DNA extracted from healthy maternal carriage, isolated in the years from 2018 to 2021 and will be sequenced at Sanger. 719 samples from the NOGBS 3 have already been sequenced at the Wellcome Sanger Institute. These bacterial samples and subsequent DNA extractions have been isolated from swabs collected from pregnant women (human source). The bacterial samples will be enriched on selective media, therefore ensuring no human DNA will be present in resulting DNA extracts.