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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]
(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. This is particularly useful in classifying streptococcal species. A substance that causes hemolysis is called a hemolysin.
The bacterial species involved in a streptococcosis infection is typically identified through microscopy of the bacteria to observe their morphology, biochemical tests (e.g., hemolysis ability), and tests on which antibodies are produced by the infected organism. [2]
The viridans streptococci are a large group of commensal streptococcal Gram-positive bacteria species that are α-hemolytic, producing a green coloration on blood agar plates (hence the name "viridans", from Latin "vĭrĭdis", green), although some species in this group are actually γ-hemolytic, meaning they produce no change on blood agar. [1]
Streptococcus bovis is a group of strains of Gram-positive bacteria, originally described as a species, [5] [6] that in humans is associated with urinary tract infections, endocarditis, sepsis, [7] and colorectal cancer. [8] S. bovis is commonly found in the alimentary tract of cattle, sheep, and other ruminants, [9] and may cause ruminal acidosis.
Nevertheless, GBS can cause severe invasive infections especially in newborns, the elderly, and people with compromised immune systems. [6] β-hemolytic colonies of Streptococcus agalactiae, blood agar 18h at 36°C. S. agalactiae is also a common veterinary pathogen, because it can cause bovine mastitis (inflammation of the udder) in dairy cows.
Across the country, infections of streptococcus bacteria of the throat are being diagnosed at quadruple the pace of the past five years, according to a health ministry report earlier this month ...
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 ...