Lab method
Bile solubility test
Pneumococcus dissolves in bile; viridans does not
High-yield clue
Bile-soluble alpha-hemolytic colonies point to Streptococcus pneumoniae, while viridans streptococci stay insoluble.
Overview
A differentiation test that uses bile salts (sodium deoxycholate) to distinguish Streptococcus pneumoniae from other alpha-hemolytic streptococci by triggering its self-lysis.
Classification
- Differential biochemical concept
- Applied to alpha-hemolytic cocci
- Reads colony/broth clearing
Lab & identification clues
- Bile salts activate pneumococcal autolysin (LytA)
- Positive = colony dissolves/broth clears
- Pairs with optochin sensitivity for pneumococcus
- Viridans streptococci are bile-insoluble
Associations
- Separates S. pneumoniae from viridans group
- Study pairing with capsule and Quellung vocabulary
- Alpha-hemolysis identification context
Commonly confused with
- Optochin test
- Viridans streptococci
Your notes
Original concept summary for coursework. Sources checked: OpenStax Microbiology 2e and NCBI Bookshelf Medical Microbiology; reviewed 2026-06. Describes vocabulary and interpretation concepts only; not a lab protocol and not for handling specimens or identifying patient isolates.