Lab #61 – Bacteriological Examination of Water: Qualitative Tests
Help!
|
|
||||
|---|---|---|---|---|---|
| Does a positive-presumptive test mean that the water is absolutely unsafe to drink? Explain. No, a positive presumptive test indicates that the water might be unsafe to drink but further testing is warranted. | No, a positive presumptive test indicates that the water might be unsafe to drink but further testing is warranted.
🗑
|
||||
| What might cause a false positive presumptive test? | A false positive presumptive test may be due to two or more non-coliform bacteria working synergistically to produce sufficient gas in the tube.
🗑
|
||||
| List three characteristics required of a good sewage indicator. | Easy to identify. Present only in sewage, not in soil. Lives slightly longer than pathogens in water.
🗑
|
||||
| What enteric bacterial diseases are transmitted in polluted water? | Typhoid fever, bacillary dysentery, and cholera
🗑
|
||||
| Name one or more protozoan diseases transmitted by polluted water. | Amoebiasis caused by E. histolytica, cryptosporidiosis caused by C. parvum, and giardiasis caused by G. lamblia.
🗑
|
||||
| Why don’t health departments routinely test for pathogens instead of using a sewage indicator? |
🗑
|
||||
| List five characteristics of coliform bacteria. | Coliform bacteria are gram-negative, facultative anaerobic, non-endospore forming bacilli that ferment lactose to produce acid and gas.
🗑
|
||||
| How is Lactose broth with Durham tube used for the detection of coliforms? | Detect gas production from lactose fermentation.
🗑
|
||||
| How is Levine EMB agar used for the detection of coliforms? | a. of gram-positive growth and lactose fermentors will produce “nucleated” colonies (black centers) and may have a metallic sheen.
🗑
|
||||
| How is Nutrient agar slant used for the detection of coliforms? | To make a slide for Gram staining to confirm morphology (gram-negative bacilli).
🗑
|
||||
| Once the completed test establishes the presence of coliforms in the water sample, why might you perform the IMViC tests on these isolates? | The IMViC tests (indole, methyl red, Voges-Proskauer, citrate) are used to confirm the identity of the isolates as coliforms. These tests will differentiate E. coli, which is associated w/ sewage, from E. aerogenes, which isn't always assoc. w/ sewage.
🗑
|
Review the information in the table. When you are ready to quiz yourself you can hide individual columns or the entire table. Then you can click on the empty cells to reveal the answer. Try to recall what will be displayed before clicking the empty cell.
To hide a column, click on the column name.
To hide the entire table, click on the "Hide All" button.
You may also shuffle the rows of the table by clicking on the "Shuffle" button.
Or sort by any of the columns using the down arrow next to any column heading.
If you know all the data on any row, you can temporarily remove it by tapping the trash can to the right of the row.
To hide a column, click on the column name.
To hide the entire table, click on the "Hide All" button.
You may also shuffle the rows of the table by clicking on the "Shuffle" button.
Or sort by any of the columns using the down arrow next to any column heading.
If you know all the data on any row, you can temporarily remove it by tapping the trash can to the right of the row.
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Created by:
michellevu