Group A streptococcus
Group A beta-haemolytic streptococcus is another name for Streptococcus pyogenes, a Gram-positive bacterial species responsible for not only bacterial pharyngitis, but also impetigo, scarlet fever, toxic shock syndrome, necrotising fasciitis and pneumococcal pneumonia. (8) S pyogenes is also associated with several specific noninfective sequelae: ARF and RHD, and acute glomerulonephritis associated with skin infections and scarlet fever. GAS is a major cause of puerperal sepsis, a significant cause of maternal mortality in previous centuries in the West, and still a problem in developing nations. (8)
[FIGURE 1 OMITTED]
Streptococcus is a spherical bacterial species that grows to form chains (see picture, p23). Streptococcus species are grouped as either alpha-haemolytic, beta-haemolytic or gamma-(non)haemolytic, depending on the manner in which they affect red blood cells in culture. Beta-haemolytic streptococci species are further separated into Lancefield groups (after Rebecca Lancefield, the American microbiologist who developed this classification system in the 1930s). Lancefield grouping is related to specific molecules on the surface of the bacteria, and their ability to trigger antibody formation. There are 20 Lancefield groups, but only groups A and B commonly cause disease in humans. (9)
Group A streptococcus Group A beta-haemolytic streptococcus is another name for Streptococcus pyogenes, a Gram-positive bacterial species responsible for not only bacterial pharyngitis, but also impetigo, scarlet fever, toxic shock syndrome, necrotising fasciitis and pneumococcal pneumonia. (8) S pyogenes is also associated with several specific noninfective sequelae: ARF and RHD, and acute glomerulonephritis associated with skin infections and scarlet fever. GAS is a major cause of puerperal sepsis, a significant cause of maternal mortality in previous centuries in the West, and still a problem in developing nations. (8) [FIGURE 1 OMITTED] Streptococcus is a spherical bacterial species that grows to form chains (see picture, p23). Streptococcus species are grouped as either alpha-haemolytic, beta-haemolytic or gamma-(non)haemolytic, depending on the manner in which they affect red blood cells in culture. Beta-haemolytic streptococci species are further separated into Lancefield groups (after Rebecca Lancefield, the American microbiologist who developed this classification system in the 1930s). Lancefield grouping is related to specific molecules on the surface of the bacteria, and their ability to trigger antibody formation. There are 20 Lancefield groups, but only groups A and B commonly cause disease in humans. (9)
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