http://sciencecases.lib.buffalo.edu/cs/files/mrsa.pdf 1. Measure the zones of in
ID: 179470 • Letter: H
Question
http://sciencecases.lib.buffalo.edu/cs/files/mrsa.pdf
1. Measure the zones of inhibition for each antibiotic on the plates shown in Figure 1 and note the measurements in the spaces in Table 1 below. (Note: Th e Kirby-Bauer method is standardized so that no zone of inhibition is scored as a 0, and all others include the disk as part of the zone.)
Key: PE = penicillin, ME = methicillin, CE = cephalothin, and VA = vancomycin Plate S. aureus MRSA 1 PE ME CE VA 2 PE ME CE VA 3 PE ME CE VA
2. Exercise 2 In Table 2 below calculate and record the averages and standard errors for each antibiotic in S. aureus and MRSA. S. aureus MRSA Average SE Average SE PE ME CE VA
1. What do you think the experimental question is?
2. What hypotheses can you come up with to answer the experimental question?
3. If your hypothesis is correct, what would the plates look like (i.e., what predictions would you make for each hypothesis)?
4. Is the experiment you just collected data for an appropriate test of the experimental question you came up with in your answer to Question 1?
5. Which antibiotics where most eff ective against S. aureus? Against MRSA?
6. When comparing the antibiotics eff ective against both, were there diff erences in eff ectiveness?
7. What other questions do the data shown in Figure 1 make you think of?
1. Describe what is happening in Figures 7 and 8 in a complete sentence of your own words.
2. What are the diff erences in how -lactam antibiotics and vancomycin work?
3. What other mechanisms might arise to allow resistance to the -lactam antibiotics?
4. Could resistance arise to vancomycin? Why or why not?
1. What do you think the experimental question is?
2. What hypotheses can you come up with to answer the experimental question?
3. What predictions would you make for each hypothesis?
4. Looking at the data in Table 1, what do these numbers mean? (Keep in mind a log value means each integer increase is actually a ten-fold increase in the number of cells.)
5. What do you think FtsZ inhibitor and imipenem are?
6. Does Table 2 change your interpretation of the experimental data from Question 4? Why or why not?
7. How eff ective was the FtsZ inhibitor alone? Imipenem alone?
8. How eff ective was the combination of the inhibitor and the -lactam antibiotic?
9. How would you explain these results?
10. What questions would you pursue next?
Explanation / Answer
1.measure the zones in mm.
2.after measuring zones of inhibition calculate the values as shown by the formulas.
1. The Experiment is testing of Antimicrobial properties of Antibiotics using Kirby-Bauer disk diffusion technique.
2.If the Zone of Inhibition is high then we can consider the Antibiotic is killing the pathogen.
3.if the Antibiotic has a higher mm of the zone of inhibition than the Antibiotic is powerful and killing the bacteria,and if the zone of inhibition is small or Absent then the bacteria has a Resistance over that Antibiotic.
4.yes.
5.PE is most Effective against S.aurus. (because it has a larger mm of zone of inhibition).
6.Yes, the difference is clear in the size of the zone of inhibition (in mm).
7.CE is also effective against S.Aurus.
1.Th e PBP takes amino acid residues attached to peptidoglycan layers and forms bridges between them within the active site groove. Th is cross-linking, or cross-bridging stabilizes and strengthens the cell wall. -lactam antibiotics interfere with the PBP enzyme by binding to the active site, blocking the site from the amino acids
2. Vanomycin bind directly to the cell wall components,whereas others form crossbridges.
3.Mutations bring Resistance to bacteria against antibiotics.
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