Streptococcus agalactiae

Streptococcus agalactiae is a gram-positivestreptococcuscharacterized by the presence of group B Lancefield antigen. It is a member of the normal flora of the gut and female urogenital tract. Early perinatal infection causes pneumonia or septicemia, which are associated with a high mortality. During delivery, a baby can acquire S. agalactiae and develop neonatal sepsis, neonatal meningitis, and 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 irratability. The polysaccharide antiphagocytic capsule is this bacterium's main virulence factor.

S. agalactiae displays beta-hemolysiswhen 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 bileand will lyse in its presence.

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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