Which organism is identified using a bile solubility test in routine clinical microbiology?

Which organism is identified using a bile solubility test in routine clinical microbiology?

• A. Streptococcus pneumoniae
• B. Streptococcus pyogenes
• C. Staphylococcus aureus
• D. Enterococcus faecalis

Answer: (A)

Bile solubility testing hinges on the fact that Streptococcus pneumoniae colonies dissolve in the presence of bile salts due to activation of their autolytic enzymes. This gives a clear, lysed appearance for pneumococcus, while other organisms do not dissolve and remain visible. In routine practice, this test identifies Streptococcus pneumoniae because it is bile soluble, whereas the other listed organisms—Streptococcus pyogenes, Staphylococcus aureus, and Enterococcus faecalis—are not lysed by bile salts and stay intact.

Bile solubility testing hinges on the fact that Streptococcus pneumoniae colonies dissolve in the presence of bile salts due to activation of their autolytic enzymes. This gives a clear, lysed appearance for pneumococcus, while other organisms do not dissolve and remain visible. In routine practice, this test identifies Streptococcus pneumoniae because it is bile soluble, whereas the other listed organisms—Streptococcus pyogenes, Staphylococcus aureus, and Enterococcus faecalis—are not lysed by bile salts and stay intact.