Which of the following is a characteristic feature on culture of Streptococcus pneumoniae organism?
These findings are used to identify Streptococcus pneumoniae. Optochin sensitivity is used to differentiate the viridans streptococci (resistant) from S. pneumoniae (sensitive). Another test used to identify S. pneumoniae is the Quellung reaction. The only medically impoant optochin-sensitive organism that gives a positive Quellung reaction is S. pneumoniae. Beta-hemolytic colonies that are bacitracin-resistant on blood agar is seen with Streptococcus agalactiae. Beta-hemolytic colonies that are inhibited by bacitracin on blood agar is seen with Streptococcus pyogenes. Catalase-negative organisms that hydrolyze esculin in 40% bile and 6.5% NaCI is seen with Enterococcus faecalis. Also Know: Pneumococci possess polysaccharide capsules of more than 85 antigenically distinct types. With type-specific antiserum, capsules swell (quellung reaction), and this can be used to identify the type. Another impoant surface component of Str. pneumoniae is a teichoic acid in the cell wall called C-substance (also known as C-polysaccharide). It is medically impoant not for itself, but because it reacts with a normal serum protein made by the liver called C-reactive protein (CRP). CRP is an "acute-phase" protein that is elevated as much as 1000-fold in acute inflammation Ref: Levinson W. (2012). Chapter 15. Gram-Positive Cocci. In W. Levinson (Ed),Review of Medical Microbiology & Immunology, 12e.
Alpha-hemolytic colonies inhibited by optochin on blood agar and lysed by bile
Beta-hemolytic colonies that are bacitracin-resistant on blood agar
Beta-hemolytic colonies that are inhibited by bacitracin on blood agar
Catalase-negative organisms that hydrolyze esculin in 40% bile and 6.5% NaCI