A narrow spectrum antibiotic is active against

Options

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

Explanation

### Step-by-Step Solution:

1. **Understanding Antibiotics**: Antibiotics are chemical substances that can kill or inhibit the growth of microorganisms, specifically bacteria. They work by interfering with the metabolic processes of these organisms.

**Hint**: Remember that antibiotics target bacteria and can either kill them or stop their growth.

2. **Defining Spectrum**: The range of bacteria that an antibiotic can affect is known as its "spectrum." This can be classified into two main categories: broad spectrum and narrow spectrum.

**Hint**: Think of "spectrum" as the variety of bacteria that an antibiotic can act upon.

3. **Broad Spectrum vs. Narrow Spectrum**:
- **Broad Spectrum Antibiotics**: Effective against a wide variety of bacteria, including both gram-positive and gram-negative bacteria.
- **Narrow Spectrum Antibiotics**: Effective against a limited range of bacteria, typically either gram-positive or gram-negative, but not both.

**Hint**: Narrow spectrum means limited action against certain types of bacteria, while broad spectrum means a wider range.

4. **Identifying Narrow Spectrum Antibiotics**: An example of a narrow spectrum antibiotic is penicillin G, which is primarily effective against gram-positive bacteria.

**Hint**: Recall that narrow spectrum antibiotics target specific types of bacteria.

5. **Evaluating the Options**: The question provides four options regarding the activity of narrow spectrum antibiotics:
- 1. Gram positive or gram negative bacteria
- 2. Gram negative bacteria only
- 3. Single organism or one disease
- 4. Both gram positive and gram negative bacteria

6. **Choosing the Correct Answer**: Based on the definitions:
- Option 1 (Gram positive or gram negative bacteria) is correct because narrow spectrum antibiotics can target either type.
- Option 2 (Gram negative bacteria only) is too restrictive.
- Option 3 (Single organism or one disease) describes a limited spectrum antibiotic.
- Option 4 (Both gram positive and gram negative bacteria) describes a broad spectrum antibiotic.

**Hint**: Analyze each option based on the definitions of narrow and broad spectrum antibiotics.

7. **Final Answer**: Therefore, the correct answer is **Option 1: Gram positive or gram negative bacteria**.