Streptococcus agalactiae Group B
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|Microbiology and Assessment of Streptococcus
๐ About
- ๐ Lancefield Group B ฮฒ-haemolytic streptococcus (Streptococcus agalactiae).
- Important pathogen in pregnant women, neonates, and immunocompromised adults.
๐ฌ Characteristics
- Aerobic or facultative anaerobe.
- Gram-positive, ฮฒ-haemolytic cocci.
- Bacitracin resistant (helps distinguish from Group A strep).
๐ Source
- Normal commensal in the genitourinary and gastrointestinal tract (โ20โ30% of women are carriers).
- Transmission may occur during delivery or via sexual contact.
โ ๏ธ Pathogenicity
- ๐คฐ Pregnancy: Endometritis, chorioamnionitis, septic abortion. Can lead to maternal sepsis.
- ๐ถ Neonates:
- Early-onset (first week): sepsis, pneumonia, meningitis.
- Late-onset (1 weekโ3 months): meningitis, bacteraemia.
- ๐งโ๐ฆณ Adults: Endocarditis, bacteraemia, soft tissue infections, osteomyelitis in vulnerable patients.
- ๐ 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).
๐งช Investigations
- Culture from blood or CSF (neonatal sepsis/meningitis).
- Antigen detection with monoclonal antibody tests.
- Antenatal rectovaginal swabs can detect maternal carriage.
๐ก๏ธ Resistance
- No significant resistance to penicillin reported.
- Resistance may occur with macrolides (erythromycin, clindamycin) โ important if penicillin-allergic.
๐ 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).
