Microbiology: An Introduction
12th Edition
ISBN: 9780321929150
Author: Gerard J. Tortora, Berdell R. Funke, Christine L. Case
Publisher: PEARSON
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Chapter 7, Problem 1A
Summary Introduction
Introduction:
The disk-diffusion method tests the effectiveness of antibiotics on a specific microorganism.
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You spread 0.1 mL volume of a 10^(-6) dilution onto a nutrient agar plate. After 24 hours of incubation at 37°C, there were 280 colonies of bacteria on the plate. A.) What is the original concentration (OCD) of bacteria in the stock sample this dilution came from? B.) Using the OCD value from part A, determine the number of colonies that would be expected to grow on a plate that is inoculated with 0.1 mL volume of 10^(-8) dilution from this same stock of bacteria. Show your work for both.
You spread 0.1 mL volume of a 10^(-6) dilution onto a nutrient agar plate. After 24 hours of incubation at 37°C, there were 280 colonies of bacteria on the plate. A.) What is the original concentration (OCD) of bacteria in the stock sample this dilution came from? B.) Using the OCD value from part A, determine the number of colonies that would be expected to grow on a plate that is inoculated with 0.1 mL volume of 10^(-8) dilution from this same stock of bacteria.
Based on the following image, which concentration of antibiotic would be considered the minimum bactericidal concentration (MBC)?
a. 8 ug/mlb. 16 ug/mlc. 25 ug/ml
Chapter 7 Solutions
Microbiology: An Introduction
Ch. 7 - The thermal death time for a suspension of...Ch. 7 - If pasteurization does not achieve sterilization,...Ch. 7 - Thermal death point is not considered an accurate...Ch. 7 - Prob. 4RCh. 7 - DRAW IT A bacterial culture was in log phase in...Ch. 7 - How do autoclaving, hot air, and pasteurization...Ch. 7 - How do salts and sugars preserve foods? Why are...Ch. 7 - Prob. 8RCh. 7 - A large hospital washes burn patients in a...Ch. 7 - Prob. 10R
Ch. 7 - Which of the following does not kill endospores?...Ch. 7 - Which of the following is most effective for...Ch. 7 - Prob. 3MCQCh. 7 - Which of the following cannot be used to sterilize...Ch. 7 - Prob. 5MCQCh. 7 - The data were obtained from a use-dilution test...Ch. 7 - The data were obtained from a use-dilution test...Ch. 7 - Prob. 8MCQCh. 7 - A classmate is trying to determine how a...Ch. 7 - Which of the following is most likely to be...Ch. 7 - Prob. 1ACh. 7 - For each of the following bacteria, explain why it...Ch. 7 - A use-dilution test was used to evaluate two...Ch. 7 - To determine the lethal action of microwave...Ch. 7 - Entamoeba histolytica and Giardia lamblia were...Ch. 7 - Between March 9 and April 12five chronic...Ch. 7 - Prob. 3CAE
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- In the Kirby-Bauer test, which of the following must be consistent? a. concentration of bacteria placed on the plate b. type of medium in the plate c. concentration of antimicrobial drug in the disk d. all of thesearrow_forwardUse the photo below to measure the diameter of each antibiotic (all 3) and record the name and measure the diameter of the zone of inhibition. AFTER, answer these questions: 1.What antiblotic is most effective against the bacteria? 2. What antibiotic is least effective against the bacteria? 3. What causes the zone of inhibition to form? 4. If you get no zone of inhibition what can you concludearrow_forwardA relatively large zone of inhibition surrounding an antimicrobial disk on a Kirby-Bauer test plate would most likely be interpreted as: a. sensitive reaction b. intermediate reaction c. resistant reactionarrow_forward
- Design a serial dilution procedure to achieve a 56-colony count, from a sample with 8.75x105 CFU/mL bacterial concentration. show solutionarrow_forwardNeutralization of residual disinfectant could be made by: a. Dilution if the concentration exponent is high b. Dilution if the concentration exponent is low c. Adding specific agent e.g. 3% Tween 80 d. Either a or c e. Either b or carrow_forwardA pure culture was inoculated onto a Mueller-Hinton agar plate. The Kirby-Bauer procedure was performed. One of the drugs tested showed a large zone of inhibition but also had small colonies growing within this zone. Further testing showed that these colonies were not the results of contamination. Why would these colonies be present within this zone of inhibition?arrow_forward
- Andrew has to prepare 30 plates (use maximum volume), 15 slants (small test tube), and 15 stabs (big test tube) of Luria Bertani Agar. a. What is the total volume of the medium needed? b. What is the amount of each component needed, given the following media composition per liter of distilled water:arrow_forwardA microbiology student was given a mixed culture of two different gram positive bacteria species to grow into a culture medium using correct aseptic techniques. After two days,one gram positive bacterial species grew on the media and the growth appeared red on the surface of the medium. Tthe second gram positive bacterial species grew and the growth appeared yellow on the surface of the medium. What is the possible explanation for the differences in the color of the bacterial growth? A. the culture was contaminated B. the microbiologist put too much inoculum on the culture medium C. the medium was a selective medium D. the medium was differentialarrow_forwardThis agar plate was obtained by spreading 0.1 ml of a 1:1,000 dilution of a bacterial sample taken from cole slaw, and then incubating at 37oC for 24h. This plate indicates that: a. there are 42 bacteria/ml on the cole slaw b. there are at least 4 different types of bacteria in the cole slaw c. there are approximately 42,000 bacteria/ml in the cole slaw sample d. there are approximately 420,000 bacteria/ml in the cole slaw e. these bacteria cannot cause illness because they came from the person’s skin who made the cole slawarrow_forward
- a) explain in your own words how to do a nitrate reduction test to identify unknown bacteria b) explain in your own words how to perform a phenol red broth (prb) test to help identify unknown bacteriaarrow_forwardYou are given a 1 gram soil sample of unknown bacterial load. After doing 10-fold serial dilutions of the soil in sterile water, 100 uL volumes are taken from each dilution for preparation of pour plates. Following incubation, each half of the 10-8 plate has 46 colonies.a) What was the dilution factor?b) How many bacteria were present in the soil?2. Staphylococcus aureus divides every 20 minutes. A culture begins with 10 bacterial cells.a) After 5 hours, how many generations have occurredb) After 5 hours, how many bacteria are present?3. How many milliliters would you need to prepare a 10-2 dilution from a 10ml starting culture?arrow_forwardThe following data were obtained from a disk-diffusion test. Antibiotic Zone of Inhibition 15 mm 0 mm 7 mm 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?arrow_forward
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