From the Guidelines
Group B Streptococcus (Streptococcus agalactiae) bacteremia primarily originates from the gastrointestinal tract, which serves as the natural reservoir for GBS, and the genitourinary tract, particularly in pregnant women where GBS colonizes the vagina and rectum, potentially leading to invasive disease. The sources of Group B strep bacteremia can be identified as follows:
- The gastrointestinal tract, which is the primary reservoir for GBS and the likely source of vaginal colonization 1
- The genitourinary tract, particularly in pregnant women, where GBS colonizes the vagina and rectum, potentially leading to invasive disease 1
- Other potential sources include skin and soft tissue infections, especially in patients with diabetes, vascular insufficiency, or other compromised skin integrity, as well as respiratory tract infections, bone and joint infections, and indwelling medical devices such as catheters or prosthetic joints 1 The bacterium's ability to evade host immune responses through its polysaccharide capsule and various virulence factors contributes to its capacity to cause invasive disease from these various sources. It is essential to note that the gastrointestinal tract serves as the natural reservoir for GBS, and vaginal colonization is often a secondary spread from this primary site 1.
In terms of specific risk factors, approximately 10%–30% of pregnant women are colonized with GBS in the vagina or rectum 1, and heavy colonization is associated with a higher risk for early-onset disease 1. Other factors that increase the risk for early-onset disease include gestational age <37 completed weeks, longer duration of membrane rupture, intra-amniotic infection, young maternal age, black race, and low maternal levels of GBS-specific anticapsular antibody 1.
Given the potential sources and risk factors, it is crucial to prioritize the prevention of perinatal Group B streptococcal disease through proper screening and intra-partum chemoprophylaxis for women who are colonized with GBS 1. This approach can significantly reduce the incidence of early-onset GBS sepsis and improve outcomes for both mothers and newborns.
From the Research
Sources of Group B Strep Bacteremia
- Group B streptococcus (GBS) is a major cause of sepsis and meningitis in newborns, and the primary risk factor for neonatal GBS early-onset disease (EOD) is maternal colonization of the genitourinary and gastrointestinal tracts 2.
- Approximately 50% of women who are colonized with GBS will transmit the bacteria to their newborns, usually during labor or after rupture of membranes 2.
- Other risk factors for GBS EOD include gestational age of less than 37 weeks, very low birth weight, prolonged rupture of membranes, intraamniotic infection, young maternal age, and maternal black race 2.
- The sources of Group B strep bacteremia can be attributed to:
- Intrapartum antibiotic prophylaxis is an effective method for preventing early-onset GBS infection in newborns, and the American College of Obstetricians and Gynecologists recommends performing universal GBS screening between 36 0/7 and 37 6/7 weeks of gestation 2.
Prevention and Management
- Routine antepartum GBS screening in pregnant women, as well as widespread use of intrapartum antibiotic prophylaxis, have aided in overall reductions in neonatal GBS disease 5.
- The key obstetric measures necessary for effective prevention of GBS EOD include universal prenatal screening by vaginal-rectal culture, correct specimen collection and processing, appropriate implementation of intrapartum antibiotic prophylaxis, and coordination with pediatric care providers 2.
- Novel testing and parturient vaccination are being explored, but barriers exist, preventing guideline updates and widespread implementation 4.