A narrow spectrum antibiotic is active against ............

Options

A. gram positive or gram negative bacteria
B. gram negative bacteria only
C. single organism or one desease
D. both gram positive and gram negative bacteria

Answer

### Step-by-Step Solution:

1. **Understanding Antibiotics**:
- Antibiotics are substances that kill or inhibit the growth of bacteria. They can be classified into two main categories: broad-spectrum antibiotics and narrow-spectrum antibiotics.

2. **Definition of Narrow Spectrum Antibiotics**:
- Narrow-spectrum antibiotics are effective against a limited range of bacteria. They target specific types of bacteria rather than a wide variety.

3. **Comparison with Broad Spectrum Antibiotics**:
- Broad-spectrum antibiotics can act on a wide range of both gram-positive and gram-negative bacteria, making them useful for treating various infections. In contrast, narrow-spectrum antibiotics are designed to target either gram-positive or gram-negative bacteria specifically.

4. **Specificity of Narrow Spectrum Antibiotics**:
- Narrow-spectrum antibiotics can be active against either gram-positive bacteria or gram-negative bacteria, but not both at the same time. They are often used when the specific type of bacteria causing an infection is known.

5. **Conclusion**:
- Therefore, a narrow-spectrum antibiotic is active against either gram-positive bacteria or gram-negative bacteria, depending on its specific action.

### Final Answer:
A narrow spectrum antibiotic is active against **gram-positive or gram-negative bacteria**.

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