Which of the following best describes a selective medium in microbiology?

• A. A culture medium that allows the growth of certain microorganisms while inhibiting the growth of others.
• B. A medium that contains indicators to distinguish between different types of microorganisms based on their metabolic properties.
• C. A nutrient-rich medium that supports the growth of most microorganisms without inhibition.
• D. A medium used to determine the antibiotic susceptibility of bacteria.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the purpose of different types of culture media in microbiology. Culture media are designed to support the growth of microorganisms, but they can have specific properties to serve different experimental goals.
2. Step 2: Define a selective medium. A selective medium contains substances that inhibit the growth of certain microorganisms while allowing others to grow. This helps isolate specific types of microbes from a mixed sample.
3. Step 3: Compare selective media with differential media. Differential media contain indicators that help distinguish between microorganisms based on their metabolic activities, but they do not necessarily inhibit growth.
4. Step 4: Recognize that nutrient-rich media support the growth of most microorganisms without selective inhibition, so they are not selective media.
5. Step 5: Identify that media used for antibiotic susceptibility testing are specialized for assessing bacterial resistance, not for selective growth, so they do not fit the definition of selective media.