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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".
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.
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.
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.
Identifying and diagnosing alpha-hemolytic Streptococcus is done with a sputum gram stain and culture test. [5] 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.
Breakpoints for the same organism and antibiotic may differ based on the site of infection: [29] for example, the CLSI generally defines Streptococcus pneumoniae as sensitive to intravenous penicillin if MICs are ≤0.06 μg/ml, intermediate if MICs are 0.12 to 1 μg/ml, and resistant if MICs are ≥2 μg/ml, but for cases of meningitis, the ...
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]
Pneumococcal infection is an infection caused by the bacterium Streptococcus pneumoniae. [1]S. pneumoniae is a common member of the bacterial flora colonizing the nose and throat of 5–10% of healthy adults and 20–40% of healthy children. [2]