Lesson 1: Staph or Strep?

Identifying bacteria is one of the most basic jobs required to diagnose many common illnesses. Since bacteria respond to different treatments, being able to categorize bacteria is a critical skill needed for all clinical practitioners. Your task is to make one of the most basic identifications: is the sample staphylococcus or streptococcus? Use the catalase test to make this determination.

Doing the science

1. Open the Bac ID simulation. Select Part I

Catalase Test
2. Select and move the slide to the middle of the tabletop.
3. Select the marker and properly label the slide.
4. Select the 3% hydrogen peroxide (H₂O₂) bottle and move the bottle to the slide. Note that two drops of H₂O₂ were placed on the slide.
5. Select one of the known bacteria samples on the top shelf and move it to the tabletop.
6. Select the inoculating loop and move the loop to the flame on the burner.
7. Move the loop to the sample plate on the table.
8. Move the loop to the two drops of H₂O₂ on the slide.
9. Select the magnifier to view the slide. Record your observations in the appropriate space in Table 1.
10. When done viewing, close the magnified view.
11. Select one of the six other samples and repeat steps 2–11. Repeat until you have tested all seven known bacteria samples.
12. Select one of the unknown bacteria samples. Make sure to write the sample code in the space in Table 1. Repeat the testing procedure with the unknown sample.
13. Using the results from your known samples testing, identify and record in Table 1 the type of bacteria in your unknown sample.