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Streptococci
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>Streptococcus anginosus group (formerly Streptococcus milleri)
1] Streptococcus intermedius
2] Streptococcus anginosus
3] Streptococcus constellatus
>Streptococcus pneumoniae
>Streptobacillus moniliformis
>Streptococcus pyogenes (Groups A, B, C, G, F)
>Streptococcus agalactiae (Group B streptococcus)
Streptococcus agalactiae:
- (also known as Group B streptococcus or GBS).
- Beta-hemolytic Gram-positive streptococcus.
- CAMP test: important test for identification. GBS (group B Streptococcus species) are screened through this test. It is characterized by the presence of group B Lancefield antigen and by its ability to hydrolyze sodium hippurate.
- Sensitive to bile, and will lyse in its presence.
- S. agalactiae’s polysaccharide antiphagocytic capsule is its main virulence factor.
- S. agalactiae is a member of the gastrointestinal normal flora in some humans and can spread to secondary sites – genitourinary tract of women 20-30%. Clinical importance: S. agalactiae can be transferred to a neonate passing through the birth canal and can cause serious group B streptococcal infection.
- S. agalactiae is the major cause of bacterial septicemia of the newborn, which can lead to death or long-term sequelae. S. agalactiae invades via alveolar and pulmonary epithelial cells; newborns are especially susceptible to infection because they lack alveolar macrophages to prevent invasion.
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