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CRA troubleshooting
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James Christopher Bohnhoff
Jul 13, 2010, 2:50:49 PM7/13/10
to biof...@magpie.bio.indiana.edu
Dear all,
Many of the questions on this list relate to Congo Red Agar, so I am hopeful that someone will relate to my experience with it. I plan on using CRA to demonstrate biofilm formation in staph grown under different conditions on agar. As mentioned in Freeman and other sources, colonies should be somewhere between pink and black, depending on biofilm formation. However, in my experience, colonies are reliably red, while agar fades and begins do show dark spots of pigment collection. The link below shows a plate in which I have removed a section of membrane on which S. aureus were growing, revealing black spots within the agar. This happens in the presence and absence of membranes. Has anyone had an experience like this? Is it to be expected, or should it affect my interpretation of staph colony morphology?
Best,
James Bohnhoff
Stanford University
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