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Streptococcus agalactiae

I. General Information

1. NCBI Taxonomy ID:

2. Disease:

Group B streptococcus (GBS) infection

3. Introduction

S. agalactiae is a member of the gastrointestinal normal flora in some humans and can spread to secondary sites - including the vagina in 10-30% of women. This is of clinical importance: S. agalactiae 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 main cause of bacterial septicemia of the newborn, which can lead to death or long-term sequelae. S. agalactiae invade via alveolar and pulmonary epithelial cells; newborns are especially succeptible to infection because they lack alveolar macrophages to prevent invasion. Newborn GBS disease is separated into early-onset disease occurring on living days 0-7 and late-onset disease which starts on days 7-90. Early-onset septicemia is more prone to be accompanied by pneumonia, while late-onset septicimia is more often accompanied by meningitis. S. agalactiae neonatal meningitis does often 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 lead to late diagnosis. Hearing loss can be a long-term sequelae of GBS-meningitis. Infection with GBS is the cause of some instances of stillbirth (Wiki: S. agalactiae).

4. Microbial Pathogenesis

Experimental study of early-onset infection suggests that this bacteria to invade fetal epithelial and endothelial cells and certain macrophages and the mortality rates for early-onset is 4-6%. This invasion is confirmed to play important role in its pathogenesis through the ability of S. agalactiae in the monkey model. Ability to invade and transcytose, this bacteria can enter into the respiratory tract causing pneumonia or further into the blood causing septicemia. Bloodstream enables this bacteria to reach different sites of body causing meningitis and osteomyelitis (MicrobeWiki: S. agalactiae).

Link to hazard mechanism of Streptococcus agalactiae in HazARD.

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