Streptococcus agalactiae Group B
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|Microbiology and Assessment of Streptococcus
📖 About
- 💉 Lancefield Group B β-haemolytic streptococcus (Streptococcus agalactiae).
- Important pathogen in pregnant women, neonates, and immunocompromised adults.
🔬 Characteristics
- Aerobic or facultative anaerobe.
- Gram-positive, β-haemolytic cocci.
- Bacitracin resistant (helps distinguish from Group A strep).
🏠 Source
- Normal commensal in the genitourinary and gastrointestinal tract (≈20–30% of women are carriers).
- Transmission may occur during delivery or via sexual contact.
⚠️ Pathogenicity
- 🤰 Pregnancy: Endometritis, chorioamnionitis, septic abortion. Can lead to maternal sepsis.
- 👶 Neonates:
- Early-onset (first week): sepsis, pneumonia, meningitis.
- Late-onset (1 week–3 months): meningitis, bacteraemia.
- 🧑🦳 Adults: Endocarditis, bacteraemia, soft tissue infections, osteomyelitis in vulnerable patients.
- 💊 Prevention: Intrapartum IV penicillin prophylaxis for colonised mothers or those at high risk (UK: offered if previous baby with GBS disease, GBS bacteriuria in current pregnancy, or detected carriage late in pregnancy).
🧪 Investigations
- Culture from blood or CSF (neonatal sepsis/meningitis).
- Antigen detection with monoclonal antibody tests.
- Antenatal rectovaginal swabs can detect maternal carriage.
🛡️ Resistance
- No significant resistance to penicillin reported.
- Resistance may occur with macrolides (erythromycin, clindamycin) - important if penicillin-allergic.
💊 Sensitivity & Treatment
- Penicillin = drug of choice.
- Alternatives if allergic: erythromycin, clindamycin, or vancomycin (guided by sensitivity).
- Supportive management in neonatal sepsis (fluids, ventilation, ITU as needed).
