Group B Streptococcal Infections: Symptoms, Types, Causes and Treatment

Group B Streptococcus (GBS), or Streptococcus agalactiae, is a bacterium that can be found in the human body without causing harm. However, under certain circumstances, it becomes a formidable pathogen, responsible for serious infections in newborns, pregnant women, and increasingly, adults with underlying conditions. Understanding GBS—its symptoms, the infections it causes, why it occurs, and how it’s treated—is crucial for both healthcare professionals and the general public. This article provides a comprehensive overview based on up-to-date scientific evidence.

Symptoms of Group B Streptococcal Infections

Group B Streptococcal infections can present in various ways depending on the age group and the affected organ system. Recognizing the symptoms promptly is essential for early diagnosis and treatment, especially in newborns and immunocompromised individuals.

Symptom	Age/Group	Common Presentations	Source(s)
Fever	All	High body temperature	2 3 5 6 10
Respiratory distress	Newborns	Grunting, rapid breathing, cyanosis	1 2 6
Apnea	Newborns	Breathing pauses	1 6
Shock	Newborns	Low blood pressure, poor perfusion	1 2
Bacteremia	All	Bloodstream infection	2 3 5 10
Meningitis	Newborns, Adults	Seizures, lethargy, irritability	2 5 6 10
Pneumonia	Newborns, Adults	Cough, difficulty breathing	3 5 6 10
Cellulitis/Soft-tissue infection	Adults	Red, swollen, tender skin	4 10
Urinary symptoms	Pregnant women, Adults	Dysuria, frequency, urgency	3 16

Table 1: Key Symptoms of Group B Streptococcal Infections

Neonatal Symptoms

Neonates are highly susceptible to GBS infections, especially in the first week of life (early-onset disease). The most common symptoms include respiratory distress, apnea, shock, and signs of sepsis. Early clinical features may mimic other conditions like respiratory distress syndrome but can be distinguished by the presence of apnea and shock in the first 24 hours and lower inspiratory pressures required during mechanical ventilation 1. Meningitis is more common in late-onset infections, presenting with seizures, irritability, lethargy, or a bulging fontanelle 2 6.

Adult Symptoms

In adults, GBS can present with a wide spectrum of symptoms. The most common manifestations are bacteremia without a clear focus, pneumonia, cellulitis, urinary tract infections, and occasionally, more severe presentations like necrotizing fasciitis and toxic shock-like syndrome 3 4 5 10. Underlying chronic illnesses, such as diabetes and cancer, predispose adults to these infections 10.

Pregnant Women

Pregnant women may develop urinary tract infections (bacteriuria), chorioamnionitis, or endometritis. Symptoms can include fever, abdominal pain, urinary discomfort, and, in severe cases, signs of sepsis 6 16.

Types of Group B Streptococcal Infections

GBS infections are classified based on the age group affected, timing, and site of infection. Each type has distinct clinical implications and outcomes.

Type	Population	Main Features	Source(s)
Early-Onset Disease (EOD)	Newborns	Sepsis, pneumonia, apnea	2 6 13 14
Late-Onset Disease (LOD)	Infants (1-12 weeks)	Meningitis, sepsis	2 6
Adult Invasive Disease	Adults	Bacteremia, pneumonia, UTI	3 5 9 10
Pregnancy-related	Pregnant women	UTI, chorioamnionitis, endometritis	6 16
Necrotizing Fasciitis/Toxic Shock	Adults	Severe soft tissue, shock	4 10

Table 2: Types of Group B Streptococcal Infections

Early-Onset Disease (EOD)

EOD occurs within the first week after birth, usually within 72 hours. It results from vertical transmission from mother to child during labor or delivery. EOD typically presents as sepsis, pneumonia, or, less commonly, meningitis. Risk factors include prolonged rupture of membranes, maternal GBS colonization, and prematurity 1 2 6 13.

Late-Onset Disease (LOD)

LOD generally appears between 1 week and 3 months of age, though it can rarely occur up to 6 months. Unlike EOD, LOD is more often associated with meningitis and is less directly linked to maternal colonization. The hypervirulent clonal complex 17 (CC17) is a common cause 2 6.

Adult Invasive Disease

In non-pregnant adults, GBS can cause a range of invasive infections: bacteremia (often without an obvious source), pneumonia, urinary tract infections, peritonitis, meningitis, and bone or joint infections 3 5 9 10. The elderly and those with chronic illnesses are at greater risk.

Pregnancy-Related Infections

Pregnant women may develop GBS urinary tract infections, chorioamnionitis (intra-amniotic infection), and postpartum endometritis. These infections can adversely affect both mother and fetus, increasing the risk of preterm birth and neonatal infection 6 16.

Necrotizing Fasciitis and Streptococcal Toxic Shock

Although rare, GBS can cause severe soft tissue infections such as necrotizing fasciitis and toxic shock-like syndrome, particularly in adults with significant underlying illnesses. These conditions are life-threatening and require urgent treatment 4 10.

Causes of Group B Streptococcal Infections

Understanding what causes GBS infections helps in formulating effective prevention and control strategies. These causes are multifactorial, involving microbial, host, and environmental factors.

Cause	Population/Context	Details	Source(s)
Maternal Colonization	Pregnant women, newborns	GBS in genitourinary/rectal sites	6 13 14 16
Vertical Transmission	Newborns	Transfer during labor/delivery	2 6 13 14
Host Immunodeficiency	All, especially adults	Diabetes, cancer, HIV, elderly	5 10
Hypervirulent Strains	Neonates, adults	CC17, serotype III, V	2 5 8 11
Nosocomial Acquisition	Adults	Hospital-acquired, invasive devices	10
Environmental/Mucosal Colonization	All	Colonization of skin, mucosa	6 11 12

Table 3: Major Causes of Group B Streptococcal Infections

Maternal Colonization and Vertical Transmission

GBS colonizes the gastrointestinal and genitourinary tracts in a significant percentage of healthy women. During labor and delivery, the bacteria can ascend and be transmitted to the newborn, leading to EOD 6 13 14 16. The risk increases with prolonged rupture of membranes and maternal GBS bacteriuria 1 16.

Host Immunodeficiency and Chronic Conditions

Adults with weakened immune systems—due to diabetes, cancer, HIV, or advanced age—are more susceptible to invasive GBS infections. These underlying conditions impair normal immune defenses, allowing GBS to invade and cause disease 5 10.

Hypervirulent Strains

Certain GBS clonal complexes, such as CC17 (linked to neonatal meningitis) and ST-1 (associated with serotype V in adults), exhibit increased virulence and adaptability, promoting invasive disease even in previously healthy hosts 2 5 8 11.

Nosocomial and Environmental Factors

Hospital-acquired cases occur, particularly in adults with indwelling devices or those exposed to invasive procedures. GBS can also colonize mucosal surfaces without causing symptoms, but under the right circumstances, this colonization can progress to invasive disease 10 11 12.

Treatment of Group B Streptococcal Infections

Timely and appropriate treatment is vital to reduce morbidity and mortality from GBS infections. Strategies differ for neonates, pregnant women, and adults, and must account for emerging antibiotic resistance.

Treatment	Indication	Key Points	Source(s)
Penicillin/Ampicillin	First-line therapy	Effective for GBS; mainstay for neonates/adults	3 5 7 16
Intrapartum Antibiotic Prophylaxis (IAP)	Pregnant women (labor)	Reduces EOD in newborns; penicillin/ampicillin	13 14 15 16
Clindamycin/Erythromycin	Penicillin allergy	Alternative; resistance increasing	3 5 7 9
Supportive Care	Severe cases, shock	Fluids, respiratory support, ICU needed	1 2 4
Surgical Debridement	Necrotizing fasciitis	Remove infected tissue; adjunct to antibiotics	4
Novel Approaches	Prophylaxis	Bacteriophage lysins, vaccine under study	12 8 11

Table 4: Common Treatments for Group B Streptococcal Infections

Antibiotic Therapy

Penicillin (or ampicillin) remains the gold standard for treating GBS infections in all age groups. These antibiotics are highly effective, although the minimum inhibitory concentrations for GBS are higher than for group A streptococci 3 5 7. For those allergic to penicillin, clindamycin or erythromycin may be used, but resistance to these drugs is rising, especially among certain serotypes 5 7 9.

Intrapartum Antibiotic Prophylaxis (IAP)

IAP involves giving antibiotics (usually penicillin or ampicillin) during labor to women identified as GBS carriers or those with GBS bacteriuria during pregnancy. This strategy has significantly reduced the incidence of EOD in newborns 13 14 15 16. However, the evidence for impact on overall mortality is less robust, and there are concerns about antibiotic overuse 14 15.

• Indications for IAP:
  • Positive GBS screening in late pregnancy
  • GBS bacteriuria at any level during current pregnancy
  • Previous infant with GBS disease
  • Intrapartum fever or prolonged rupture of membranes (>18 hours) 16

Management of Special Cases

• Neonatal Infections: Prompt empirical antibiotic therapy, supportive care, and close monitoring are crucial. Meningitis and severe sepsis may require intensive care 1 2 6.
• Necrotizing Fasciitis: Requires urgent surgical debridement alongside antibiotics 4.
• GBS Bacteriuria in Pregnancy: High colony counts (≥100,000 CFU/mL) warrant treatment during pregnancy, but even low counts should prompt IAP at delivery 16.

Emerging and Future Therapies

• Bacteriophage Lysins: Experimental therapies using enzymes that specifically target GBS are under study and have shown promise in animal models 12.
• Vaccines: Several GBS vaccines are in development, aiming to prevent both neonatal and adult disease, particularly from hypervirulent strains 8 11.

Conclusion

Group B Streptococcal infections remain a significant health concern, particularly for newborns, pregnant women, and adults with underlying conditions. Early recognition, risk-based prevention strategies, and effective antibiotic treatment are essential to reduce the burden of disease.

Key Takeaways:

• Symptoms of GBS infections vary by age and type, ranging from mild to life-threatening (e.g., sepsis, meningitis, pneumonia, soft-tissue infections).
• Types of infection include early- and late-onset neonatal disease, invasive adult infections, and severe forms like necrotizing fasciitis.
• Causes involve maternal colonization, vertical transmission, host immunodeficiency, and hypervirulent bacterial strains.
• Treatment centers on penicillin-based antibiotics, with IAP being crucial in preventing neonatal disease; resistance to alternative antibiotics is rising, and new therapies are under investigation.

Staying informed about GBS and its management is vital for both healthcare providers and the public to ensure early detection, prompt treatment, and, ultimately, better health outcomes.