Microbiology Case Study

4.Questions

1. Define coliforms.

- Of or relating to the bacilli that commonly inhabit the intestines of humans and other vertebrates, especially the colon bacillus.

2. Why do we test for coliforms instead of individual pathogens to determine if water is safe to drink?

- Coliform testing is cheaper and faster than testing for individual pathogens and allows them to decide whether or not water is safe in a more efficient time.

3. In this problem, what would be the likely result of the Confirmed test if the health care workers omitted the Presumptive test and performed the Confirmed test first?

- The Presumptive test, test for lactose and the Confirmed test then proceeds to test the found lactose to see if it is safe or not to drink. Without the Presumptive test you would not have the lactose to perform the second test.

4. A student observed gas formation in all 5 of the lactose broth tubes in the Presumptive test but the EMB plates in the Confirmed test showed no growth. What could the student conclude about the organisms present in the original water sample?

- The student should conclude that the water sample is safe to drink.

5. What was the source of contamination of the pond (spring, pipe, ditch, stream or pond)?

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6. Why isn't a Presumptive test sufficient to determine if water is safe to drink?

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7. List five waterborne diseases and their etiologic agents.

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8. A student obtained the following results in the Completed test from a sample of water taken from his family's well. Should he drink the water? Why or why not?

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