Lesson 6: The BEA Test: Which Type of Strep?

Bile esculin agar (BEA) is a selective differential medium used to identify Enterococcus and group D Streptococci. Only bacteria capable of hydrolyzing esculin to glucose and esculetin produce a dark black color in the medium. The medium remains a beige color for all other bacteria. Can you complete your bacteria identification for the specific species of Streptococcus using the results from the bile esculin agar slant tube test?

Doing the science

1. Open the Bac ID simulation. Select Part II.

Sample Preparation
2. Select one of the known streptococcus bacteria samples from the top shelf and move it to the tabletop. Do not choose a staphylococcus bacteria sample.
3. Select the 0.85% saline tube from the shelf and move it to the tabletop.
4. Select the inoculating loop and move the loop to the burner flame.
5. To collect a sample, move the sterilized loop to the plate containing the known streptococcus bacteria sample on the table.
6. Move the loop from the sample plate to the 0.85% saline test tube

Bile Esculin Agar Slant Tube Test
7. Select the bile esculin agar (BEA) slant tube from the shelf and move it to the tabletop.
8. Select the marker and label the BEA tube with the name of the bacteria.
9. Select the inoculating loop and move the loop to the burner flame.
10. Move the loop to the 0.85% saline tube
11. Move the loop to the BEA slant tube.
12. Move the BEA slant tube to the incubator.
13. When the incubation period is complete, select the magnifier.
14. Carefully observe the sample. Note and record your observations in the appropriate space on Table 1. Close the magnified view.
15. Repeat steps 2–14 for the remaining Streptococcus bacteria samples only. Do not choose a Staphylococcus bacteria sample. Make sure to record your results in Table 1.
16. Repeat steps 2–14 for one of the unknown bacteria samples on the top shelf.
17. Make sure to enter the code for the unknown sample in Table 1.
18. Using the results from your analysis, identify the bacteria type in your unknown sample. Record the name of your unknown bacteria type in Table 1.