Performance should include plating on media that enables differentiation between gram-negative and gram-positive organisms. It should also include an explanation of the media types, examples of each, and their purposes:
- CNA (colistin naladixic acid) agar isolates gram-positive bacteria.
- EMB (eosin methylene blue) agar isolates gram-negative bacteria.
- MacConkey agar isolates gram-negative bacteria.
- Selective vs. differential media
Process/Skill Questions:
- How does CNA agar isolate gram-positive bacteria?
- Which media would be useful in isolating E. coli? What components of the agar make this possible?
- What is the difference between nutritive, enrichment, selective, and differential media?