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Beta-hemolysis (β-hemolysis), sometimes called complete hemolysis, is a complete lysis of red cells in the media around and under the colonies: the area appears lightened (yellow) and transparent. [1] Streptolysin, an exotoxin, is the enzyme produced by the bacteria which causes the complete lysis of red blood cells. There are two types of ...
A red blood cell in a hypotonic solution, causing water to move into the cell A red blood cell in a hypertonic solution, causing water to move out of the cell. Hemolysis or haemolysis (/ h iː ˈ m ɒ l ɪ s ɪ s /), [1] also known by several other names, is the rupturing of red blood cells (erythrocytes) and the release of their contents into surrounding fluid (e.g. blood plasma).
Alpha-hemolytic species cause oxidization of iron in hemoglobin molecules within red blood cells, giving it a greenish color on blood agar. Beta-hemolytic species cause complete rupture of red blood cells. On blood agar, this appears as wide areas clear of blood cells surrounding bacterial colonies. Gamma-hemolytic species cause no hemolysis. [11]
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.
As mentioned, S. agalactiae is a Gram-positive coccus with a tendency to form chains, beta-haemolytic, catalase-negative, and facultative anaerobe (anaerobic organism).GBS grows readily on blood agar plates as microbial colonies surrounded by a narrow zone of β-haemolysis.
The name group A (beta-hemolytic) Streptococcus is thus also used. [ 1 ] The species name is derived from Greek words meaning 'a chain' ( streptos ) of berries ( coccus [Latinized from kokkos ]) and pus ( pyo )-forming ( genes ), since a number of infections caused by the bacterium produce pus.
Streptococcus anginosus may be beta-hemolytic or nonhemolytic. The small colonies often give off a distinct odor of butterscotch or caramel. Among the nonhemolytic strains, certain ones produced the alpha reaction on blood agar. [3]
It is a beta-hemolytic, catalase-negative, and facultative anaerobe. [1] [2] 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).