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Streptococcus salivarius is a species of spherical, gram-positive, facultative anaerobic lactic acid bacteria [1] that is both catalase and oxidase negative. S. salivarius colonizes (usually in chains) the oral cavity and upper respiratory tract of humans just a few hours after birth, making further exposure to the bacteria harmless in most circumstances.
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.
Streptococcus salivarius; Streptococcus saliviloxodontae [1] ... beta-hemolytic. Streptococcus dysgalactiae subsp. canis [20] is the predominant subspecies ...
This group is referred to as alpha-hemolysis because the cell membrane of red blood cells is left intact. [2] When cultured, alpha-hemolysis can be deemed present when the agar gel appears greenish. [2] Identifying and diagnosing alpha-hemolytic Streptococcus is done with a sputum gram stain and culture test. [5]
Bacteria of the genus Enterococcus, formerly known as group D streptococci, were classified as members of the genus Streptococcus until 1984 and are included in the original Lancefield grouping. [4] Many—but not all—species of streptococcus are beta-hemolytic .
Streptococcus thermophilus formerly known as Streptococcus salivarius subsp. thermophilus [2] [1] is a gram-positive bacterium, and a fermentative facultative anaerobe, of the viridans group. [3] It tests negative for cytochrome, oxidase, and catalase, and positive for alpha-hemolytic activity. [3] It is non-motile and does not form endospores. [3]
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]
In addition to strict anaerobic bacteria, microaerophilic streptococci and Streptococcus salivarius can also be present. Fusobacterium spp. and anaerobic spirochetes are often the cause of acute necrotizing ulcerative gingivitis (or Vincent's angina) which is a distinct form of ulcerative gingivitis.