Streptococcus agalactiae (also known as group B streptococcus or GBS) is a gram-positive coccus (round bacterium) with a tendency to form chains (as reflected by the genus name Streptococcus). It is a beta-hemolytic, catalase-negative, and facultative anaerobe.S. agalactiae is the most common human pathogen of streptococci belonging to group B of the Rebecca Lancefield classification of streptococci. GBS are surrounded by a bacterial capsule composed of polysaccharides (exopolysacharide). The species is subclassified into ten serotypes (Ia, Ib, II–IX) depending on the immunologic reactivity of their polysaccharide capsule.The plural term group B streptococci (referring to the serotypes) and the singular term group B streptococcus (referring to the single species) are both commonly encountered (even though S. halichoeri and S. pseudoporcinus are also group B Streptococci). In general, GBS is a harmless commensal bacterium being part of the human microbiota colonizing the gastrointestinal and genitourinary tract of up to 30% of healthy human adults (asymptomatic carriers). Nevertheless, GBS  can cause severe invasive infections especially in newborns, the elderly, and people with compromised immune systems. S. agalactiae is also a common veterinary pathogen, because it can cause bovine mastitis (inflammation of the udder) in dairy cows. The species name agalactiae meaning "of no milk", alludes to this. Laboratory identification
GBS grows readily on blood agar plates as colonies surrounded by a narrow zone of β-hemolysis. GBS is characterized by the presence in the cell wall of the antigen group B of Lancefield classification (Lancefield grouping) that can be detected directly in intact bacteria using latex agglutination tests.
This theory is based on high incidence of dead parasites or ova within stone in autopsy findings. Diagnosis
The diagnosis can be suspected by imaging, with typical characteristics centering around appearance of the liver, typically with CT, ultrasound or MRI. Traits that raise suspicion for the infection include intra- and extra- hepatic dilatation and strictures with intraductal pigmented stones, usually in the absence of gallstones and with regions of segmental liver atrophy, particularly the lateral aspect of the left hepatic lobe. There is also reduced arborization of peripheral ducts. Approximately 5% of chronic infections go on to develop cholangiocarcinoma.Pathogenic bacteria responsible for the infection include E. coli, Klebsiella, Pseudomonas, and Proteus species. Anaerobes are a less frequent cause, and a culture positive for multiple strains can be common. When related to Clonorchis sinensis, definitive diagnosis is by identification of eggs by microscopic demonstration in faeces or in duodenal aspirate, but other sophisticated methods have been developed, such as ELISA, which has become the most important clinical technique. Diagnosis by detecting DNAs from eggs in faeces are also developed using PCR, real-time PCR, and LAMP, which are highly sensitive and specific. Treatment
The treatment of RPC involves management of sepsis during episodes of cholangitis with antibiotics, abscess drainage, and blood pressure support. With resistant infection, a surgical hepatectomy or hepaticocutaneousjejunostomy can be performed. Lifelong surveillance for malignancy is also usually necessary. See also
Cholangitis
Cholecystitis
Clonorchiasis
Clonorchis sinensis
Hepaticojejunostomy
Cirrhosis

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