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The hemolysis of some weakly beta-hemolytic organisms is enhanced when streaked close to certain beta hemolytic strains of Staphylococcus aureus. This phenomenon is the mechanism behind the CAMP test , [ 2 ] a test that was historically used for the identification of Streptococcus agalactiae and Listeria monocytogenes . [ 3 ]
The level of alpha-toxin expressed by a particular strain of S. aureus directly correlates with the virulence of the strain. [2] Recent research has shown that immunization with a mutant form of alpha-toxin that is no longer able to form pores protects against S. aureus pneumonia in mice. Also, introduction of alpha-toxin specific antibodies ...
Alpha-hemolysin from uropathogenic E. coli produces extra-intestinal infections and can cause cystitis, pyelonephritis, and sepsis. Alpha-hemolysin from Staphylococcus aureus can cause severe diseases, such as pneumonia. Aerolysin from Aeromonas sobria infects the intestinal tract, but it might also cause sepsis and meningitis.
Streptococcus mitis is a species of Gram-positive, mesophilic, alpha-hemolytic bacteria in the genus Streptococcus.These bacteria are facultative anaerobes, and made up of non-motile and non-sporing cocci (round cells) that are catalase negative.
In colonial morphology, hemolysis is classified into three types: alpha-, beta-, and gamma-hemolysis. In alpha-hemolysis, the blood is partially digested, causing the area around the colony to turn green. In beta-hemolysis, the organism digests the blood completely, leaving a clear area around each colony.
Enterococci exhibit variable hemolysis on blood agar. Differences occur between species, and between strains of species. More virulent organisms are more likely to exhibit alpha (partial) or beta (complete) hemolysis than less virulent specimens of Enterococcus, which frequently exhibit gamma (absent) hemolysis. [5]
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] However, of isolates examined in one study, 56% were non-hemolytic, 25% were beta-hemolytic, and only 19% were alpha-hemolytic. [4]
Alpha toxin or alpha-toxin refers to several different protein toxins produced by bacteria, including: Staphylococcus aureus alpha toxin , a membrane-disrupting toxin that creates pores causing hemolysis and tissue damage