Group B Strep
Group B Strep (GBS), or Streptococcus agalactiae, is a common bacterium that naturally lives in the digestive and lower genital tracts of many healthy people. While Group B Strep is usually harmless in adults, it can cause serious infections in newborns, pregnant women, and individuals with weakened immune systems. Understanding this organism is critical, especially for expecting mothers and healthcare providers, as it is a leading cause of life-threatening infections in newborns.
Group B Streptococcus is part of the normal microbiota in about 20–40% of healthy women and men. However, problems arise when the bacteria are transmitted from mother to baby during childbirth, potentially causing conditions like sepsis, pneumonia, or meningitis. Fortunately, with appropriate screening and preventive antibiotics during labour, most GBS infections in newborns can be avoided.
Colonisation vs. Infection
It’s important to distinguish between GBS colonisation and GBS infection:
Colonisation means the bacteria are present without causing harm
Infection occurs when the bacteria multiply uncontrollably and invade sterile areas like the bloodstream, lungs, or brain
Most adults who carry GBS will never experience symptoms or complications. In fact, GBS is not considered a sexually transmitted infection and can coexist harmlessly in many people for years.
Who Is at Risk?
While GBS rarely causes illness in healthy adults, it can lead to severe disease in:
Newborns (especially in the first week of life)
Pregnant women (due to hormonal and immune changes)
Older adults with chronic conditions (e.g. diabetes, cancer, or heart disease)
People with compromised immune systems
Newborns are most at risk due to their immature immune defences and exposure during delivery.
How GBS Affects Newborns
Group B Strep can cause two types of infections in babies:
1. Early-Onset GBS Disease
Occurs in the first 0–6 days after birth
Usually acquired during childbirth
Symptoms include:
Fever
Breathing difficulties
Lethargy or poor feeding
Seizures or abnormal movements
Early-onset GBS can lead to sepsis, pneumonia, or meningitis, often requiring emergency care.
2. Late-Onset GBS Disease
Occurs between 7 days and 3 months of age
May be acquired from the environment or close contact
Can also cause meningitis or sepsis
Risk is not reduced by antibiotics given during labour
While less common than early-onset, late-onset GBS is equally serious and may result in long-term neurological damage.
Symptoms in Pregnant Women
Pregnant individuals may develop:
Urinary tract infections
Intra-amniotic infections (chorioamnionitis)
Postpartum endometritis
Preterm labour or rupture of membranes
In rare cases, GBS may enter the bloodstream, causing maternal sepsis, which can be life-threatening if not treated promptly.
Other Adult Presentations
In adults with weakened immune systems, GBS can lead to:
Bloodstream infections
Skin and soft tissue infections
Bone and joint infections
Pneumonia or urinary tract infections
These infections often require hospitalisation and intravenous antibiotics.
Screening for Group B Strep
In many countries, pregnant women are offered routine screening for GBS between 35 and 37 weeks’ gestation. This involves:
A vaginal and rectal swab
Testing for GBS colonisation
Results guide the use of antibiotics during labour
In regions without routine screening, a risk-based approach is used, focusing on factors like:
Previous baby with GBS
GBS in the urine during this pregnancy
Fever during labour
Preterm labour (<37 weeks)
Preventing Transmission During Birth
For colonised women, intravenous penicillin (or an appropriate alternative for allergies) is given during labour. This significantly reduces the baby’s risk of infection. Antibiotics are only given during labour—not before—because early treatment may not prevent colonisation at delivery.
Key facts:
Antibiotics are most effective when started at least 4 hours before delivery
Planned caesarean sections before labour typically do not require GBS prophylaxis
Is GBS Treatable?
Yes. GBS responds well to antibiotics such as:
Penicillin (first-line treatment)
Ampicillin
Vancomycin (for penicillin-allergic patients)
Newborns suspected of infection are given intravenous antibiotics immediately, often before test results confirm the diagnosis. Close monitoring in a neonatal unit may be required.
Breastfeeding and GBS
Breastfeeding is safe and encouraged even if the mother carries GBS. Breast milk contains protective antibodies and helps strengthen the baby’s immune system. There is no evidence that breastfeeding increases the risk of GBS infection.
Global Perspective and Public Health
Not all countries screen for GBS universally. Some use risk-based screening, while others recommend routine testing. Organisations like the World Health Organization (WHO) continue to evaluate the cost-effectiveness and feasibility of implementing universal GBS prevention strategies in low- and middle-income countries.
In high-resource settings, universal screening and intrapartum antibiotics have significantly reduced early-onset GBS disease. Ongoing vaccine research aims to offer longer-term protection for both mother and baby.
Conclusion | Group B Strep
Group B Strep is a common bacterium that lives harmlessly in many adults but can cause serious infections in newborns and vulnerable individuals. With proper screening, timely use of antibiotics, and increased awareness, most cases of early-onset Group B Strep disease can be prevented. As global healthcare systems continue to improve access to antenatal care, the burden of GBS-related complications can be reduced further.
