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Group B streptococcal infection, also known as Group B streptococcal disease or just Group B strep infection, is the infectious disease caused by the bacterium Streptococcus agalactiae. Streptococcus agalactiae is the most common human pathogen belonging to group B of the Lancefield classification of streptococci —hence the name of group B ...
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. [1] [2] S. agalactiae is the most common human pathogen of streptococci belonging to ...
In the medical setting, the most important groups are the alpha-hemolytic streptococci S. pneumoniae and Streptococcus viridans groups, and the beta-hemolytic streptococci of Lancefield groups A and B (also known as "group A strep" and "group B strep"). Table: Medically relevant streptococci [10]
Hemolyses of Streptococcus spp. (left) α-hemolysis (S. mitis); (middle) β-hemolysis (S. pyogenes); (right) γ-hemolysis (non-hemolytic, S. salivarius) Hemolysis is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on blood agar is used to classify certain microorganisms.
[2] [7] An additional method used to identify B-hemolytic streptococci is the PYR test, which is primarily used in distinguishing S. pyogenes from other B-hemolytic strains by testing for the presence of pyrrolidonyl aminopeptidase. [2] Both the Lancefield antigen grouping sera and PYR test are widely available for commercial usage.
The CAMP test (Christie–Atkins–Munch-Petersen) is a test to identify group B β-hemolytic streptococci (Streptococcus agalactiae) [1] [2] based on their formation of a substance, CAMP factor, [3] that enlarges the area of hemolysis formed by the β-hemolysin elaborated from Staphylococcus aureus.
Group A streptococcal infections are a number of infections with Streptococcus pyogenes, a group A streptococcus (GAS). [1] S. pyogenes is a species of beta-hemolytic Gram-positive bacteria that is responsible for a wide range of infections that are mostly common and fairly mild.
Bacteria of the genus Enterococcus, formerly known as group D streptococci, were classified as members of the genus Streptococcus until 1984 and are included in the original Lancefield grouping. [4] Many—but not all—species of streptococcus are beta-hemolytic .