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Swedish University of Agricultural Sciences

Veterinary bacteriology: information about important bacteria
Veterinary bacteriology


Species/Subspecies: Streptococcus agalactiae
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:
Phylum
Firmicutes
Class
Bacilli
Order
Lactobacillales
Family
Streptococcaceae 
Genus
Streptococcus
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-glucoselactosemaltoseL-rhamnosesucrose
+v+?+
L-arabinosecellobioseD-mannitolsalicintrehalose
-?-v+
glycerolinulinraffinoseD-sorbitolstarch
+---?
Other carbohydrates: Amygdalin -, ribose +.
Microbiological tests:
Streptococcus agalactiae  
CAMP test positive.
Spec. Char.: S. agalactiae produces polysaccharide capsules of about 10 different antigenic types, which all contains sialic acid.
Special Media:
Streptococcus agalactiae  Streptococcus agalactiae  Streptococcus agalactiae  
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.

Disease:
HostsDiseaseClinical picture
CattleMastitisContagious mastitis that can cause both acute and chronic mastitis, clinical and subclinical.
Humans (newborn)Meningitis and sepsisCommon in the vaginal flora, the baby is infected through the respiratory tract in connection with birth.
Virulence Factors: Antiphagocytic capsule
Genome Sequence:
Acc-noStrainSize (bp)Genome
NC_004368 NEM316 2 211 485 1c + 0 

16S rRNA Seq.:
Acc-noStrainNumber of NTOperon
AB002479 ATCC 13813T 1 450 

Taxonomy/phylogeny:
 
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:2021-10-11

News

The revised taxonomy of the mollicutes

The revised taxonomy of mollicutes (mycoplasmas) has now been introduced on VetBact, which means that many of the species have been given new genus names or moved to another higher taxon. 

Published 2021-11-25. Read more...

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