Development and Optimization of a GBS Diagnostic Test

Group B Streptococcus (GBS), also known as Streptococcus agalactiae, is a gram-positive diplococcus originally known for causing bovine mastitis and was not demonstrated to be a human pathogen until 1938. In the 1970s, GBS emerged as the leading cause of neonatal morbidity and mortality. GBS causes severe invasive disease in newborns. Approximately 80% of infections in young infants occur within the first week of life and are thus designated as early-onset disease. Late-onset infections usually occur in infants between 1 week and 3 months of age. Young infants with invasive GBS disease usually have sepsis or pneumonia but may, though less frequently, present with meningitis, osteomyelitis, or septic arthritis. Bloodstream infections, with or without pneumonia, are the main manifestation of neonatal GBS disease and are observed in approximately 90% of cases, while meningitis occurs in around 10%. Most early-onset disease results from ascending spread of GBS into the amniotic fluid, which leads to neonatal colonization and to invasive disease in some infants. Perinatal transmission of the organism can occur through both ruptured and intact membranes. Transmission from mother to child has been reported to be 29 times higher in GBS-colonized mothers than in noncolonized mothers. The new Centers for Disease Control and Prevention guidelines recommend universal prenatal culture-based screening for GBS colonization in all pregnant women. A more sensitive rapid-screening test for GBS that could accurately detect women who carry GBS at the time of delivery would obviate the need for prenatal screening while reducing the risk associated with the use of intrapartum prophylaxis with antibotics in non-colonized women. The main objective of the study is to develop and optimize a micro TAS prototype for rapid GBS detection directly from vaginal/anal specimens using swabs collected from pregnant women admitted for delivery. It is expected that this diagnostic system can replace the current "gold standard" which is microbiological culture in selective media for determining GBS colonization. Specific objectives of this study include: (1) analytical sensitivity of the micro TAS prototype (number of GBS colony forming units detected per vaginal/anal specimen) will be determined by using prospectively collected vaginal/anal specimens positive for GBS as well as negative vaginal/anal specimens that will be spiked with various numbers of GBS cells; (2) specificity of the micro TAS prototype (ability to detect specifically GBS nucleotide sequences without detecting other microbial species or human sequences) will be determined by using GBS-negative vaginal/anal specimens and; (3) sample analysis and performance of the micro TAS prototype will be compared to clinical samples with FDA-approved BD GeneOhm StrepB assay . Study participants will include 320 pregnant females between 18 to 44 years of age, who are admitted to the Centre Hospitalier Universitaire de Québec for delivery. Participation involves being observed for 30 minutes. The research nurse will obtain 2 vaginal/anal samples using standard techniques. One sample will be used to detect GBS with the approved BD GeneOhm StrepB assay and the other sample will be used for the development of the new point-of-care rapid detection GBS test.