Streptococcus pneumoniae undergoes autolysis in the presence of bile salts.
Bile salts: sodium deoxycholate, sodium taurocholate
Mechanism: activation of autolysins (autolytic enzymes)
Use: To distinguish Streptococcus pneumoniae from other streptococci
Media
Positive Result on Exposure to Bile Salt Solution
Incubation at 35°C
broth culture
clearing (reduced turbidity)
3 hours
agar plate
colony disappears
30 minutes
False negative:
(1) pH <= 6.5
(2) pneumococcal strains with no or low autolytic enzyme activity
(3) failure to incubate for a long enough period
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Specialty: Clinical Laboratory, Infectious Diseases
