| Species/Subspecies: | Streptococcus agalactiae | |||||||||
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| Categories: | Zoonotic; causes hemolysis | |||||||||
| Etymology: | Genus name: twisted (like a chain) cocci (coccus means a grain or a berry and referrs to any spherical microorganism) Species epithet: from lack of milk. | |||||||||
| Significance: | [Very important] | |||||||||
| Taxonomy: | Class Bacilli Order Lactobacillales Family Streptococcaceae Genus Streptococcus |
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| Type Strain: | ATCC 13813 = CCUG 4208 = NCTC 8181. | |||||||||
| Macromorphology (smell):
| Small (approximately 1 mm in diameter) transluscent colonies after incubation for 24 h at 37°C. Many (but not all) strains give a (clear) zone of beta-hemolysis on blood agar. The hemolysis zone can be very thin or broad. | |||||||||
| Micromorphology: | Nonmotile cocci (less than 2 µm in diameter) in chains. The chains are often longer if the bacteria originate from a fluid culture. | |||||||||
| Gram +/Gram -: | G+ | |||||||||
| Metabolism: | Facultatively anaerobic | |||||||||
| Catalase/Oxidase: | -/- | |||||||||
| Other Enzymes: | Esculinase -, hippuricase +, coagulase -, urease - | |||||||||
| Biochemical Tests: | Voges-proskauer (+) | |||||||||
| Fermentation of carbohydrates: | D-glucose + lactose v maltose + L-rhamnose ? sucrose + L-arabinose - cellobiose ? D-mannitol - salicin v trehalose + glycerol + inulin - raffinose - D-sorbitol - starch ? |
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| Microbiological tests:
| CAMP test positive. | |||||||||
| Spec. Char.: | S. agalactiae produces polysaccharide capsules of about 10 different antigenic types, which all contains sialic acid. | |||||||||
| Special Media:
| Purple agar with lactose is used to investigate if bacteria can ferment lactose under acid production.
SELMA- or SELMA Plus plates are used for cultivation of milk samples from suspected mastitis cases. |
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| Disease: |
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| Virulence Factors: | Antiphagocytic capsule | |||||||||
| Genome Sequence: |
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| 16S rRNA Seq.: |
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| Taxonomy/phylogeny:
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About 100 species have been described within the genus Streptococcus. Many species within the genus Enterococcus have earlier been classified as streptococci and, thus, they are closely related. S. agalactiae is closely related to S. dysgalactiae. | |||||||||
| Comment: | Belongs to Lancefield's group B streptcocci. | |||||||||
| Updated: | 2023-03-08 |