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Streptococcus agalactiae

  • General information


    • Streptococcus agalactiae = Lancefield Group B

      Taxonomy

      Family: Streptococcaceae

      Natural habitats
      Isolated from human urogenital tract and intestine

      Clinical significance
      They are the cause of invasive neonatal infections.

      Neonatal infections present as two different clinical entities
      - early onset neonatal disease, characterized by sepsis and pneumonia within the first 7 days of life
      - late onset disease with meningitis and sepsis between 7 days and 3 month of age.

      The most important risk factor for the development of invasive neonatal disease is the colonization, urogenital by S.agalactiae, which is found by pregnant women

      Infections of adult patients may be observed as postpartum infections or in immunocompromised adult patients with alcoholism, diabetes mellitus, cancer or AID’s.

      The spectrum of infections in adult patients includes pneumonia, bacteremia, endocarditis, urinary tract infections, skin and soft tissue infections and osteomyelitis

  • Diseases

  • Gram stain

    • Gram positive streptococci,

      grouped in pairs, short to long chains

      Liquid medium,
      they are found in the form of chains of different lengths.

      They namely divide into one direction

  • Culture characteristics

    • Beta-hemolytic streptococci of the pyogenic group (S. pyogenes, S. agalactiae, and S. dysgalactiae ssp equisimilis) form colonies > 0.5 mm

      Viridans streptococci form colonies < 0.5 mm

      Facultative anaerobic


      5% CO2 improves the growth

      BA: colonies > 0.5 mm after 24 hours of incubation

      They appear grey or almost white, moist or glistening.

      S. agalactiae produces the largest colonies with a relative small zone of hemolysis.

      McConkey: growth

      BBAØ: growth

  • Characteristics

  • References

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