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Bacteria under Microscope
Streptococcus agalactiae
Group B streptococcus, GBS
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Gram-stain: |
Gram-positive cocci |
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Microscopic appearance: |
Short chains of cocci, diplococci |
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Clinical significance: |
- Streptococcus agalactiae is a member of the gastrointestinal normal flora in some humans.
- In the western world, S. agalactiae is the major cause of bacterial septicemia of the newborn, which can lead to death or long-term sequelae.
- S. agalactiae is present in up to one-third of women of childbearing age, and 1.8 cases per 1000 live births will be affected by group B streptococcal infection.
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Text: Wikipedia |
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Colony morphology: |
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A |
B |
C |
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| Streptococcus agalactiae identification |
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A |
Beta-hemolytic colonies of Streptococcus agalactiae (Group B streptococcus, GBS) on sheep blood agar. Cultivation 24 hours, aerobic atmosphere, 37°C. |
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B |
Colonies of S.agalactiae surrounded by a zone of beta-hemolysis. Colonies of group B streptococci often have less pronounced zones of beta-hemolysis than do other beta-hemolytic streptococci (e.g. from Group A or C); some group B strains are nonhemolytic.
Cultivation 24 hours in an aerobic atmosphere, 37°C. Sheep blood agar |
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C |
CAMP reaction. Streptococcus agalactiae produce extracellular, diffusible protein (CAMP factor) that acts synergistically with beta-lysin produced by Staphylococcus aureus to produce a zone of enhanced lysis of sheep (or bovine) erythrocytes. Cultivated on Columbia agar with 5% defibrinated sheep blood, 24 hours in an aerobic atmosphere, 37°C.
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www.bacteriainphotos.com |
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