Microbiology: An Introduction (13th Edition)
13th Edition
ISBN: 9780134605180
Author: Gerard J. Tortora, Berdell R. Funke, Christine L. Case, Derek Weber, Warner Bair
Publisher: PEARSON
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Chapter 20, Problem 4A
The following data were obtained from a disk-diffusion test.
| Antibiotic | Zone of Inhibition |
| A | 15 mm |
| B | 0 mm |
| c | 7 mm |
| D | 15 mm |
- a. Which antibiotic was most effective against the bacteria being tested?
- b. Which antibiotic would you recommend for treating a disease caused by this bacterium?
- c. Was antibiotic A bactericidal or bacteriostatic? How can you tell?
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A pure bacterial culture of unknown concentration was diluted to determine the
concentration of viable bacteria in the original culture. Serial dilutions were performed as
1.
diagrammed below. Each dilution tube contained 400 ul of diluent and 100 ul was transferred
into each tube. TSA plates were inoculated with 100 µul from the last three dilution tubes.
a. What is the dilution between each tube shown in the diagram below? Express your
answer as a ratio.
b. What is the total dilution of tube number 5? Express your answer as a ratio.
c. What is the concentration of viable bacteria in the original culture? Express your
answer using scientific notation and the units CFU/ml.
d. What is the concentration of viable bacteria in tube number 2? Express your answer
using the units CFU/ml.
e. If you inoculated a TSA plate with 250 µl from tube number 5, how many colonies would
you expect to see after the plate was incubated?
1
2
3
5
423
80
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Number of colonies
A pure bacterial culture of unknown concentration was diluted to determine the
concentration of viable bacteria in the original culture. Serial dilutions were performed as
2.
diagrammed below. A volume of 500 µl was transferred into each tube. TSA plates were
inoculated with 100 µl from the last three dilution tubes.
a. If the dilution between each tube is 102, what is the volume of diluent in each of the 5
dilution tubes? Provide the volume using ml as the units.
b. What is the total dilution of tube number 4? Express the total dilution using scientific
notation.
c. What is the concentration of viable bacteria in the original culture? Express the
concentration using scientific notation and CFU/ml as the units.
d. If you inoculated a TSA plate with 1.0 ml from dilution tube 4, how many colonies would
you expect to form on the plate after incubation?
e. If the original culture had a volume of 50ml, what was the total number of viable
bacteria in the 50 ml of the original culture?
1 2
3…
What is the purpose of diluting a culture by making "quadrant streaks" (or "streak plating") bacteria, and what can we use them for? Check all that apply
A.
To observe colony morphology/color
B.
To isolate viral plaques
C.
testing growth conditions or treatments (such as media, antibiotics, incubation temperature etc.,)
D.
To isolate a clonal population of bacteria from the rest of the culture
E.
For subculturing (transferring to new media so we can grow more bacteria, storing the plate in a fridge for repeated use so the bacteria don't die quickly)
F.
Accurate quantification (to calculate CFU/mL)
G.
To know what strain of bacteria you're working with, since you can tell based on how it looks on the plate.
H.
To lower risk of contamination/identify contamination
Chapter 20 Solutions
Microbiology: An Introduction (13th Edition)
Ch. 20 - DRAW IT Show where the following antibiotics work:...Ch. 20 - List and explain five criteria used to identify an...Ch. 20 - What similar problems are encountered with...Ch. 20 - Define drug resistance. How is it produced? What...Ch. 20 - List the advantages of using two chemotherapeutic...Ch. 20 - Why does a cell die from the following...Ch. 20 - How does each of the following inhibit...Ch. 20 - The OH is missing from carbon 39 in ddI. How does...Ch. 20 - Compare the method of action of the following...Ch. 20 - NAME IT This microorganism is not susceptible to...
Ch. 20 - Which of the following pairs is mismatched? a....Ch. 20 - Prob. 2MCQCh. 20 - Prob. 3MCQCh. 20 - An antimicrobial agent should meet all of the...Ch. 20 - The most selective antimicrobial activity would be...Ch. 20 - Prob. 6MCQCh. 20 - Which of the following will not affect eukaryotic...Ch. 20 - Cell membrane damage causes death because a. the...Ch. 20 - A drug that intercalates into DNA has the...Ch. 20 - Chloramphenicol binds to the 50S portion of a...Ch. 20 - Prob. 1ACh. 20 - Why is idoxuridine effective if host cells also...Ch. 20 - Some bacteria become resistant to tetracycline...Ch. 20 - The following data were obtained from a...Ch. 20 - Prob. 5ACh. 20 - The following results were obtained from a broth...Ch. 20 - Vancomycin-resistant Enterococcus faecalis was...Ch. 20 - Prob. 2CAECh. 20 - Prob. 3CAE
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