Bile solubility test

The bile solubility test is used to determine the ability of bacterial cells to lyse in the presence of bile salts, within a specified time and temperature.

S. pneumoniae possesses an autolytic enzyme, an amidase, which lyses the cell’s own wall during division. The addition of bile salts (sodium deoxycholate) activates the autolytic enzyme and the organisms rapidly autolyse. Other α-haemolytic streptococci do not possess such an active system and therefore do not dissolve in bile. The bile solubility test may be performed in two different ways:

• using a cell suspension or
• by applying the Bile solubility Reagent directly to the colony.

Public Health England has opened a consultation on the standard test method. For details see: UK Government Gateway: https://www.gov.uk/government/consultations/uk-smi-tp-5-bile-solubility-test

Posted by Dr. Tim Sandle