9.2: MSA Media Procedure
MSA Media Procedure
Name: _____________________________________________________
Course Section: ______________________________________________
The following activity will teach students how to inoculate an MSA plate. Post-inoculation, students will use their colony growth to determine if the bacteria are halophilic and verify mannitol utilization.
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Step 1:
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Step 2:
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Step 3:
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Step 4:
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Results
In the table below, record your observations for colonies grown in MSA media.
| Species | Growth (+/-) | Salt resistance (+/-) | Medium color surrounding growth | Mannitol fermentation (+/-) |
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| Staphylococcus saprophyticus |
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| Staphylococcus epidermidis |
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| Escherichia coli |
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General Questions
1. Define selective medium.
2. Explain how MSA is a selective medium.
3. Define differential medium.
4. Explain how MSA is a differential medium.
5. Explain how phenol red, a component of MSA, detects if a species conducts mannitol fermentation.
6. Explain the role of MSA in differentiating between commensal skin flora and potentially pathogenic bacteria present in clinical samples obtained from skin infections.
Health-Related Questions
1. Mannitol salt agar plates are used to differentiate between bacteria that belong to what genus?
2. What bacteria causes MRSA?
3. Why is MRSA a significant concern for healthcare workers?
4. How do we use mannitol salt agar to determine if a patient is infected with S. epidermidis or S. aureus?