This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Amoxicillin + clavulanic acid is active against the following organisms EXCEPT : 
Select and explain. 
A. Methicillin resistant Staph. aureus, B. Penicillinase producing Staph. aureus, C. Penicillinase producing N. gonorrhoeae, D. β-lactamase producing E. coli
A: Methicillin resistant Staph. aureus
Answer: A: Methicillin resistant Staph. aureus 
Explanation: Staphylococcus aureus develops resistance to methicillin by acquiring altered penicillin-binding proteins that have low affinity. No Beta-lactam antibiotic is effective against MRSA.
Clavulanic acid is an inhibitor of β-lactamase. It can restore the sensitivity of penicillins against the organisms who have developed penicillinases.