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Case: |
And
what's hiding in your sponge? |
Part 1.
Jane had a long series of irritating skin
rashes. She had been to several doctors, but none
of them came up with a diagnosis -- all the samples they
sent to the lab came back as negative for pathogenic bacteria.
Finally, one nurse suggested she bring in her shower sponge
and washcloth. When the loofa sponge was squeezed,
a green slime, the same color as her shower gel, came out.
Samples of the sponge and wash cloth were sent to the lab
for culture. The lab routinely uses enriched media,
to be sure to find all organisms present.
Part 2.
Results from the lab:
Sample 1 (wash cloth): no growth after 48 hours
Sample 2 (loofa sponge): Pseudomonas
aeruginosa
Explain these results.
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Case Author: Julie Harless
Montgomery College, jharless@nhmccd.edu
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Case Analysis
Possible issues:
Nutritional requirements of bacteria.
Physical conditions for bacterial growth.
Opportunistic infections.
Methods of sanitation.
Option: Include a know / need to know chart
like the one below:
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What do you know?
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What do you need
to know?
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Learning Goals
- Identifiy basic
growth requirements for bacteria
- Understand that
different organisms have different nutritional requirements
- Be able to distinguish
between minimal and enriched medium
- Have experience
with experimental design
- Practice collaboration
skills
- Gain confidence
in applying information to a new situation.
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Investigations and Activities
Laboratory exercises:
1. Directed type of laboratory: students
test different standard media for their ability to support growth
of different bacteria (Pseudomonas, Staphylococcus, E. coli).
Results of this exercise can then be used as background information
and a starting place for group experiment.
2. In groups, students will be asked to design a growth medium
that will support growth of Pseudomonas aeruginosa, but will
not allow E. coli growth.
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Resources
Text book
General information web sites:
http://commtechlab.mus.edu/sites/dlc-me/zoo/zdhmain.html
http://www.sciencenet.com.au/bacteriiologyhome.htm
http://star.tau.ac.il/~inon/publications/multicellular_abs.html
Medical Microbiology
http://www.emedicine.com/PED/topic2701.htm
Web sites of Microbiology courses:
http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/101syllabus97.html#lecschedule
http://www.bact.wisc.edu/Bact303/NutrutionandGrowth
http://fhis.gcal.ac.uk/BIO/micro/drjrattray/nutmicro/growth.html
Lab Manual Appendix, media recipes
Difco Manual, media recipes
Modeling software for microbial growth
simulations:
- Micro GCK (BioQUEST)
- Biota (BioQUEST)
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Handouts
Directions for one page analysis
Lab protocol for standard media tests
Analysis chart for selective media experiment.
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Student Products
Group: List of issues to be investigated.
Individuals: Short (one page) analysis
of case.
Entries in lab notebook of results and interpretation of standard
media tests.
Group: Outline of experiment to
design a selective medium.
Report with background, experimental results, and conclusions.
Recommendations for types of sponges that will not support
microbial growth.
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Assessment and Evaluation Plan
5% Initial analysis of case in group discussion.
List should include some of the topics in learning goals. (Grade
in class, give feedback before they start writing individual analyses.)
25% One page individual analysis of case.
Looking for understanding of the different growth conditions in
a sponge and a cloth, the basic requirements for living organisms.
20% Flow chart for standard media assay,
results and interpretation of results.
20% Design of experiment for selective
medium
a.
components that are necessary for all organisms
b.
which components will be varied, which constant
30% Results of experiment: group
lab report with background, results and conclusions. Report
form included with explicit outline of nutritional requirements.
Recommendation of types of sponges that will not support bacterial
growth.
Terminology and application questions included
on exam.
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Implementation
Identify the specifics for using the cases in
your classes.
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Course name:
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Microbiology |
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Likely sequence in
syllabus:
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Time during term:
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Week 3-4
in the semester |
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Duration:
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1.5 weeks |
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Setting:
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Classroom
discussion, laboratory |
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Students in course:
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Sophomore,
allied health, some biology majors |
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Collaborative elements:
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Group discussions
in class to define the problem, identify resources.
Groups in lab to perform first experiment, design
and perform second experiment, written group report
for experiment 2. |
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Credits
Photographs: Neal Chamberlain, Kenneth
Todar, Bernard A. Cohen, Chrisoph U. Lehmann
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