Group B Streptococcus Colonization in Mother-newborn Dyads and Association With Serotype-specific Capsular Antibodies in Karachi, Pakistan.

Group B Streptococcus (GBS) of which there are 10 serotypes of varying invasive potential is a major cause of invasive bacterial disease in neonates and young infants. Approximately two-thirds of invasive GBS disease occurs during the first three days of life of which 75%-90% occur within 24 hours of birth in the absence of clinical interventions such as intrapartum antibiotic prophylaxis (IAP). Invasive GBS disease during the first week (Early onset disease, EOD) of life results from vertical acquisition of GBS in utero by the foetus or during labour from recto-vaginally colonized women. The incidence of EOD in full-term new-borns has declined by approximately 90% in countries where there is routine screening of pregnant women for GBS recto-vaginal colonization at 35-37 weeks of gestational age and where IAP is provided 4 hours prior to delivery to colonized women. The strategy for routine screening for GBS colonization coupled with IAP, however, is not logistically feasible in most resource-constrained countries including Pakistan and has also been shown to be not cost-effective including in some high-income countries. The current CDC recommendation for the isolation of GBS from vaginal and rectal or recto-vaginal swabs is by initial growth in a selective broth medium with antibiotics, followed by subculture on blood agar or selective media.

This study aims to address the knowledge gaps to better inform the epidemiology of GBS in a low income setting and address some of the critical limitations of current data from low-middle income countries. Women who had normal vaginal delivery at term (>37 weeks of gestation age) will be enrolled in this study. Recto-vaginal swabs from the mothers will be collected for GBS.

All samples will be collected by trained midwives/physician before delivery. All newborns born to these mothers will be followed at 28th day after birth to assess their health status with emphasis on possible invasive disease episodes.