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Streptococcus agalactiae also known as Group B Streptococcus (cocci) is a gram-positive streptococcus characterized by the presence of group B Lancefield antigen. These bacteria cause Group B streptococcal infection. Streptococcus agalactiae is a species of the normal flora of the gut and female urogenital tract. Early perinatal infection causes septicemia, pneumonia or meningitis, which are associated with a high mortality. During delivery, a baby can acquire S. agalactiae and develop neonatal sepsis, neonatal meningitis, and/or neonatal pneumonia. Neonates with meningitis do not present with the hallmark sign of adult meningitis, a stiff neck. They display nonspecific symptoms such as fever, vomiting, poor feeding, and irritability. The polysaccharide antiphagocytic capsule is this bacterium's main virulence factor.
S. agalactiae displays beta-hemolysis when cultured on a blood agar plate and produce zones of hemolysis that are only slightly larger than the colonies themselves. Group B streptococci hydrolyze sodium hippurate and give a positive response in the CAMP test. S. agalactiae is also sensitive to bile and will lyse in its presence.
[edit] References
- 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.
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