Differentiate the microscopic morphology of streptococci and pneumococci
as seen by Gram stain.

2. What type of hemolysis is produced by S. pneumoniae?

Question

Differentiate the microscopic morphology of streptococci and pneumococci
as seen by Gram stain.

2. What type of hemolysis is produced by S. pneumoniae?

thomaster · Answer

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Streptococcus pneumoniae is alpha hemolytic.
Do you know what that means?

anonymous · Answer

v The minimum criteria for identification and distinction of pneumococci from other streptococci are bile or optochin sensitivity, Gram-positive staining, and hemolytic activity. Pneumococci cause alpha hemolysis on agar containing horse, human, rabbit and sheep erythrocytes. Under anaerobic conditions they switch to beta hemolysis caused by an oxygen-labile hemolysin. Typically, pneumococci form a 16-mm zone of inhibition around a 5 mg optochin disc, and undergo lysis by bile salts (e.g. deoxycholate). Addition of a few drops of 10% deoxycholate at 37°C lyses the entire culture in minutes. The ability of deoxycholate to dissolve the cell wall, depends upon the presence of the autolytic enzyme, LytA. Virtually all clinical isolates of pneumococci harbor the autolysin and undergo deoxycholate lysis.