Growth of the organism in the presence of bile supports identification as which organism in this scenario?

• A. Growth inhibited by bile
• B. Growth not inhibited by bile
• C. It forms spores
• D. It is Gram-positive

Answer: (B)

Bile tolerance is the giveaway trait here. Enterococcus species can grow in the presence of bile, whereas many other Gram-positive cocci—such as non-enterococcal streptococci—are inhibited by bile. So when you see that the organism continues to grow in a bile-containing medium, it strongly points to Enterococcus rather than organisms that are inhibited by bile. This trait is often used in conjunction with esculin hydrolysis on bile-esculin agar to confirm identification, since Enterococcus not only grows in bile but also hydrolyzes esculin, giving a characteristic dark reaction. While being Gram-positive is true for Enterococcus, that broad description doesn’t distinguish it from many other bacteria, so the specific ability to grow in bile is the critical identifying feature.