An 86 yr old male complains of cough and blood in his sputum for the past two days. On admission, his temperature is 103deg F. physical examination reveals rales in his right lung, and x- ray examination shows increased density in the right middle lobe. A sputum smear shows many Gram positive coci, confirmed by sputum culture as penicillinase producing staphylococcus aureus. Which of the following agents should be given?
High-Yield Explanation
Unlike the other listed drugs, oxacillin is resistant to penicillinase. The other four agents are broad-spectrum penicillins, while oxacillin is generally specific for Gram-positive microorganisms. Use of penicillinase resistant penicillins should be reserved for infections caused by penicillinase producing staphylococci.