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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 ...
Human microbiota are microorganisms (bacteria, viruses, fungi and archaea) found in a specific environment. They can be found in the stomach, intestines, skin, genitals and other parts of the body. [1] Various body parts have diverse microorganisms. Some microbes are specific to certain body parts and others are associated with many microbiomes.
However, both Streptococcus dysgalactiae and the Streptococcus anginosus group can possess group A antigen as well. Group A streptococci, when grown on blood agar, typically produce small (2–3 mm) zones of beta-hemolysis, a complete destruction of red blood cells. The name group A (beta-hemolytic) Streptococcus is thus also used. [1]
Enterococcus faecalis – formerly classified as part of the group D Streptococcus system – is a Gram-positive, commensal bacterium inhabiting the gastrointestinal tracts of humans. [ 1 ] [ 2 ] Like other species in the genus Enterococcus , E. faecalis is found in healthy humans and can be used as a probiotic.
Graphic depicting the human skin microbiota, with relative prevalences of various classes of bacteria. The human microbiome is the aggregate of all microbiota that reside on or within human tissues and biofluids along with the corresponding anatomical sites in which they reside, [1] [2] including the gastrointestinal tract, skin, mammary glands, seminal fluid, uterus, ovarian follicles, lung ...
Similarly, group B streptococcus typically denotes Streptococcus agalactiae, although minor beta-hemolytic group B streptococci like S. troglodytidis exist. [15] While most streptococcal illnesses in humans originate from species adapted to humans, such as S. pneumoniae or S. pyogenes, there are zoonotic species capable of causing infections. [15]
Though there are many groups of streptococci, the principal organisms that are known to cause human disease belong to group A (Streptococcus pyogenes), group B (Streptococcus agalactiae), group C/G (Streptococcus dysgalactiae) both members of group D (Streptococcus gallolyticus and Streptococcus infantarius, both members of the Streptococcus ...
The genus Streptococcus has around 129 species and 23 subspecies [16] that benefit many microbiomes on the human body. There are many species that show non-pathogenic characteristics; however, there are some, like S. pneumoniae, that exhibit pathogenic characteristics in the human body. [17] [11]