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The quellung reaction, also called the Neufeld reaction, is a biochemical reaction in which antibodies bind to the bacterial capsule of Streptococcus pneumoniae, Klebsiella pneumoniae, Neisseria meningitidis, Bacillus anthracis, Haemophilus influenzae, [1] Escherichia coli, and Salmonella.
Streptococcus pneumoniae can be differentiated from the viridans streptococci, some of which are also alpha-hemolytic, using an optochin test, as S. pneumoniae is optochin-sensitive. S. pneumoniae can also be distinguished based on its sensitivity to lysis by bile, the so-called "bile solubility test".
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 ...
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]
Griffith's experiment discovering the "transforming principle" in Streptococcus pneumoniae (pneumococcal) bacteria. Griffith's experiment , [ 1 ] performed by Frederick Griffith and reported in 1928, [ 2 ] was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation .
For decades, Streptococcus pneumoniae has been considered susceptible to optochin; but some strains have been found to be resistant to optochin in laboratory testing. This is notable because the emergence of optochin-resistant strains would invalidate the distinguishing test described above.
[1] [9] The results of antimicrobial susceptibility tests performed during a given time period can be compiled, usually in the form of a table, to form an antibiogram. [31] [32] Antibiograms help the clinician to select the best empiric antimicrobial therapy based on the local resistance patterns until the laboratory test results are available ...
Viridans streptococci can be differentiated from Streptococcus pneumoniae using an optochin test, as viridans streptococci are optochin-resistant; they also lack either the polysaccharide-based capsule typical of S. pneumoniae or the Lancefield antigens of the pyogenic members of the genus. [5]