Question

multiple select question
select all that apply
which of the following are selective agents used in microbiological media? more than one answer may be correct.

• chocolate
• nutrient agar
• antibiotics
• bile salts

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Explanation:

1. Chocolate (media component): Chocolate agar is an enriched medium (not selective) as it provides nutrients for fastidious organisms. So it's not a selective agent.
2. Nutrient agar: It's a general - purpose medium that supports the growth of a wide range of bacteria, so it's not a selective agent.
3. Antibiotics: Antibiotics can be used as selective agents in microbiological media. For example, if we add an antibiotic that inhibits the growth of gram - positive bacteria to a medium, it will select for gram - negative bacteria to grow.
4. Bile salts: Bile salts are selective agents. They inhibit the growth of many gram - positive bacteria and are used in media (like MacConkey agar) to select for gram - negative enteric bacteria.

Answer:

C. antibiotics, D. bile salts