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Streptococcus agalactiae
Scientific classification
Kingdom: Bacteria
Phylum: Firmicutes
Class: Bacilli
Order: Lactobacillales
Family: Streptococcaceae
Genus: Streptococcus
Species: S. agalactiae
Binomial name
Streptococcus agalactiae
Lehmann and Neumann, 1896

Streptococcus agalactiae (also known as Group B streptococcus or GBS) is a beta-hemolytic gram-positive streptococcus.



CAMP test is an important test for its identification. Mainly GBS are screened through this test. It is characterized by the presence of group B Lancefield antigen and by its ability to hydrolyze sodium hippurate.[1]

It is also sensitive to bile and will lyse in its presence.

S. agalactiae's polysaccharide antiphagocytic capsule is its main virulence factor.

Clinical significance

S. agalactiae is a species of the normal flora of the female urogenital tract and rectum. Its chief clinical importance is that it can be transferred to a neonate passing through the birth canal and can cause serious group B streptococcal infection. 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 can also cause neonatal meningitis, which does not present with the hallmark sign of adult meningitis, a stiff neck; rather, it presents with nonspecific symptoms such as fever, vomiting and irritability and can consequently go undiagnosed until it is too late. Hearing loss can be a long-term sequelae of GBS-meningitis. Somewhat more rarely, S. agalactiae can also cause invasive group B streptococcal disease of the adult in the pregnant, elderly, or immunosuppressed.

S. agalactiae is present in up to one-third of women of childbearing age, and one in every thousand live births will be affected by group B streptococcal infection.

In the elderly or persons with compromised immune systems septicemia or other serious infections are seen. This occurs also rarely during pregnancy or maternity.


There is no reliable way to prevent the disease currently, however prophylactic treatment with antibiotics (typically intravenous penicillin) during delivery is the prevention measure most commonly used. Vaccination of adolescent women is considered an ideal solution; however, though research for the development of such a vaccine is underway, a good candidate vaccine has yet to surface.

Different western countries use different strategies to select which women in labor are most likely to need antibiotics.

  • The United States uses the most aggressive strategy: all pregnant women are screened for S. agalactiae[2] and prophylactic antibiotics are given to all positive women. Because of this strategy, America has seen a marked reduction in babies born with early-onset infection.
  • Most European countries do not generally screen, but use a risk-based strategy at time of delivery.


  1. ^ Smith JP, Durfee KK, Marymont JH (March 1979). "A review of laboratory methods for identification of group B streptococci (Streptococcus agalactiae)". Am J Med Technol 45 (3): 199–204. PMID 371403.  
  2. ^ Apgar BS, Greenberg G, Yen G (March 2005). "Prevention of group B streptococcal disease in the newborn". Am Fam Physician 71 (5): 903–10. PMID 15768620.  
  • Brooks, Geo F., Janet Butel, and Stephen Morse. Jawetz, Melnick, and Adelberg's Medical Microbiology, 22nd edition. 2001.
  • Gillespie, Stephen and Kathleen Bamford. Medical Microbiology at a Glance. 2000.

External links



Up to date as of January 23, 2010

From Wikispecies


Main Page
Superregnum: Bacteria
Regnum: Bacteria
Phylum: Firmicutes
Classis: Bacilli
Ordo: Lactobacillales
Familia: Streptococcaceae
Genus: Streptococcus
Genus: Streptococcus agalactiae
Species: Streptococcus agalactiae serogroup V - Streptococcus agalactiae serogroup III - Streptococcus agalactiae 18RS21 - Streptococcus agalactiae 515 - Streptococcus agalactiae H36B - Streptococcus agalactiae COH1 - Streptococcus agalactiae CJB111 - Streptococcus agalactiae serogroup Ia - Streptococcus agalactiae str. Camel -



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