Which of the following antibiotics is not effective against infections casued by gram negative bacteria.

Options

A. Penicillin
B. Amoxillin
C. Ampicllin
D. All the three

Answer

To determine which antibiotic is not effective against infections caused by gram-negative bacteria, we need to analyze the types of antibiotics mentioned and their effectiveness against different types of bacteria.

### Step-by-Step Solution:

1. **Understand Antibiotics**: Antibiotics are medications used to treat infections caused by bacteria. They can be classified into two main categories: narrow-spectrum antibiotics and broad-spectrum antibiotics.

- **Narrow-Spectrum Antibiotics**: These antibiotics are effective against specific types of bacteria. They are not effective against all bacteria.
- **Broad-Spectrum Antibiotics**: These antibiotics can target a wide range of bacteria, including both gram-positive and gram-negative bacteria.

2. **Identify the Antibiotics**: The antibiotics mentioned in the question are:
- Penicillin
- Amoxicillin
- Ampicillin

3. **Analyze Each Antibiotic**:
- **Penicillin**: This is a narrow-spectrum antibiotic primarily effective against gram-positive bacteria. It is not very effective against gram-negative bacteria.
- **Amoxicillin**: This is also a narrow-spectrum antibiotic. It is mainly used to treat urinary tract infections and is not effective against gram-negative bacteria.
- **Ampicillin**: Similar to the others, ampicillin is a narrow-spectrum antibiotic that is effective against specific bacteria, particularly those causing respiratory tract infections, but it is not effective against gram-negative bacteria.

4. **Conclusion**: Since all three antibiotics (Penicillin, Amoxicillin, and Ampicillin) are narrow-spectrum antibiotics and are not effective against gram-negative bacteria, the answer to the question is that all of them are not effective against infections caused by gram-negative bacteria.

5. **Final Answer**: The correct option is **D) All of the above**.