Search results
Results from the WOW.Com Content Network
Streptococcus mutans is a facultatively anaerobic, gram-positive coccus (round bacterium) commonly found in the human oral cavity and is a significant contributor to tooth decay. [ 1 ] [ 2 ] The microbe was first described by James Kilian Clarke in 1924.
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]
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.
Streptolysin O is an oxygen-sensitive cytotoxin, secreted by most group A Streptococcus (GAS), and interacts with cholesterol in the membrane of eukaryotic cells (mainly red and white blood cells, macrophages, and platelets), and usually results in beta-hemolysis under the surface of blood agar. Streptolysin S is an oxygen-stable cytotoxin also ...
Main Streptococcus groups are included as "Strep." at bottom left. Diagnosis is by a swab of the affected area for laboratory testing. A Gram stain is performed to show Gram-positive cocci in chains. Then, the organism is cultured on blood agar. The rapid pyrrolidonyl arylamidase (PYR) test is commonly used, wherein a positive reaction confers ...
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 system, created by Rebecca Lancefield, was historically used to organize the various members of the family Streptococcaceae, which includes the genera Lactococcus and Streptococcus, but now is largely superfluous due to explosive growth in the number of streptococcal species identified since the 1970s. [2]
Streptococcus sanguinis White and Niven 1946 S. sanguinis is a normal inhabitant of the healthy human mouth where it is particularly found in dental plaque , where it modifies the environment to make it less hospitable for other strains of Streptococcus that cause cavities , such as Streptococcus mutans .