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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]
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] A modified version of this test called the reverse CAMP test, utilizing S. agalactiae instead of S. aureus, can also be used to identify Clostridium perfringens.
However, it has retained some clinical usefulness even after the taxonomic changes, [1] and as of 2018, Lancefield designations are still often used to communicate medical microbiological test results. The classification assigns a letter code to each serotype. There are 20 described serotypes assigned the letters A to V (excluding E, I and J). [3]
The anginosus group streptococci are members of the viridans streptococci group. [1] They have been implicated as etiologic agents in a variety of serious purulent infections, but because of their heterogeneous characteristics, these organisms may be unrecognized or misidentified by clinical laboratorians. [ 2 ]
Main Streptococcus groups are included as "Strep." at bottom left. In clinical practice, the most common groups of Streptococcus can be distinguished by simple bench tests, such as the PYR test for group A streptococcus. There are also latex agglutination kits which can distinguish each of the main groups seen in clinical practice.
Further identification can be done serologically to test for the presence of capsular antigen, which is the dominant structure on the surface of S. pneumoniae. [2] [5] Bile solubility can be used to further distinguish S. pneumoniae from viridans streptococci as S. pneumoniae are bile soluble and viridans streptococci are not. [6]
Streptococci. It is usually caused by a form of Viridans group streptococcus bacteria that normally live in the mouth [3] (Streptococcus mutans, mitis, sanguis or milleri). [2] Other strains of streptococci can cause subacute endocarditis as well.
Streptococcus oralis is a Gram positive viridans streptococcus of the Streptococcus mitis group. [2] [3] S. oralis is one of the pioneer species associated with eubiotic dental pellicle biofilms, and can be found in high numbers on most oral surfaces. [4] [5] It has been, however, found to be an opportunistic pathogen as well. [2]