Amoxicillin+clavulanic acid is active against the following organisms EXCEPT:: (A) Methicillin resistant Staph. aureus, (B) Penicillinase producing Staph. aureus, (C) Penicillinase producingN. gonorrhoea, (D) b-lactamase producing E.coli
Answer is A. (Ref: KDT 6/e p702, 703) Staphylococcus aureus develops resistance to methicillin by acquiring altered penicillin binding proteins that have low affinity. No b-lactam antibiotic is effective against MRSA. Clavulanic acid is n inhibitor of b-lactamase. It can restore the sensitivity of penicillins against the organisms who have developed penicillinases.