Microbiology Fundamentals: A Clinical Approach
3rd Edition
ISBN: 9781260163698
Author: Cowan
Publisher: MCG
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Chapter 2, Problem 17Q
After performing the streak plate procedure on a bacterial specimen, the culture was incubated. When you viewed the plate there was heavy growth with no isolated colonies in the first quadrant. There was no other growth on the plate (in second quadrant and beyond). Discuss possible errors that could have led to this result.
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Students have asked these similar questions
if an unknown bacterial slide appears to be in fading color and the shape of the specimen seems to be diffused. what troubleshooting of the focusing is needed in order to see the bacteria clearly?
you are given a mix culture of S aureus, E. coli and P. aeruginosa. besides using the streak plate method what other method could you choose to separate the bacteria? the result you will be looking for and interprete the result.
A bacterial culture was grown for 12 hours. At 4-hour interval, the culture was sampled to
determine the population of the culture, by transferring 25 ml of the suspension to 225 ml
0.90% NaCl. Three consecutive dilutions were further made by using I ml aliquot in 9 ml of
0.90% NaCl. One ml from each dilution was plated in each of duplicate plates. The
following table shows the results of the plating method.
田
Sampling
COUNTS
1st dilution
54; 61
2nd dilution
3rd dilution
4h dilution
1st
3; 7
0; 0
0,0
2nd
TNTC
TNCT
242: 233
28: 37
3rd
TNTC
TNTC
INTC
249-246
* TNTC = Too numerous to count
i. Illustrate the dilution series used and label the final dilution of each dilution.
ii. Determine the bacterial count (CFU/ml) every 4 hours of incubation for 12 hours. Show all
computations.
Chapter 2 Solutions
Microbiology Fundamentals: A Clinical Approach
Ch. 2.1 - Explain what the Five Is are and what each step...Ch. 2.1 - Discuss three physical states of media and when...Ch. 2.1 - Compare and contrast selective and differential...Ch. 2.1 - Provide brief definitions for defined media and...Ch. 2.1 - Medical Moment The Making of the Flu Vaccine: An...Ch. 2.1 - Prob. 1NPCh. 2.1 - Prob. 2NPCh. 2.2 - Prob. 5AYPCh. 2.2 - Prob. 6AYPCh. 2.2 - Prob. 7AYP
Ch. 2.2 - Give examples of simple, differential, and special...Ch. 2.2 - Prob. 3NPCh. 2.2 - Medical Moment Gram-Positive Versus Gram-Negative...Ch. 2 - The identities of microorganisms on our planet a....Ch. 2 - Prob. 2QCh. 2 - Often bacteria that are freshly isolated from a...Ch. 2 - Which of these types of organisms is least likely...Ch. 2 - Prob. 5QCh. 2 - Some bacteria can produce a structure called an...Ch. 2 - A fastidious organism must be grown on what type...Ch. 2 - Write a short paragraph to differentiate among the...Ch. 2 - Prob. 9QCh. 2 - Viruses are commonly grown in/on a. animal cells...Ch. 2 - Can you devise a growth medium with ingredients...Ch. 2 - There is a type of differential medium that can...Ch. 2 - Prob. 13QCh. 2 - Several bacteria live naturally in a material on...Ch. 2 - Archaea often grow naturally in extreme...Ch. 2 - Prob. 16QCh. 2 - After performing the streak plate procedure on a...Ch. 2 - You are a scientist studying a marsh area...Ch. 2 - Prob. 19QCh. 2 - Prob. 20QCh. 2 - You perform the special stain for bacterial...Ch. 2 - Prob. 1VC
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- You are given a bacterial culture which has a concentration of approximately 5.0 x 10^8 cells/mL. List a series of dilutions and platings that you could carry out in order to determine the exact concentration of the culture. Note that you must plate four plates from a minimum of two dilution tubes. The volumes plated should be in the range of 0.1 mL – 1.0 mL. Duplicate volumes may not be plated from any one dilution tube. Each plating should aim for a count between 30 and 300 CFUs. You can select any value from 30-300 for CFU and any volume from 0.1-1.0 to find out dilution schemearrow_forwardUsing your fingers, you are asked to aseptically touch the surface of a sterile agar plate. Illustrate the possible result from this step if your fingers are (a) unwashed – touched various things prior to placing on agar surface, and (b) washed with soap or disinfected with 70% alcohol. Describe the relative abundance of microbial growth observed on the plates. List and draw the possible characteristics of an isolated bacterial colony that can be observed based on type of (a) margin, (b) elevation, (c) texture, and (d) optical property.arrow_forwardIn the preparation of a bacterial smear, why is there a need to fix the bacteria to the slide? Aside from passing the slide over a flame, what are the other ways of fixing the bacteria to the slide?arrow_forward
- during inoculation, the bacterial culture tube is always held at an angle and the lid of the Petri dish is slightly open. Explain the purpose of these steps briefly.arrow_forwardAfter performing a Gram stain on a Gram negative bacteria, the specimen does not show pink or purple bacteria. Which of the following could notexplain why this occurred? Decolorizer was used after safranin Safranin was not used Crystal violet was not used The specimen was not heat-fixedarrow_forwardHow do we reconcile the number of colonies in the plates to the actual number of bacteria in the original sample? Count Plate Methodarrow_forward
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