<prompt> A 65-year-old male from bihar with a pneumonia has a sputum culture that is positive for a staphylococcal strain that is b-lactamase- positive. Which is the best choice of penicillin therapy in this patient?AmpicillinOxacillinTicarcillinPenicillin G  <response>: Oxacillin is classified as a penicillinase-resistant penicillin that is relatively acid-stable and, therefore, is useful for oral administration. Major adverse reactions include penicillin hypersensitivity and interstitial nephritis. With the exception of methicillin, which is 35 bound to serum proteins, all penicillinase-resistant penicillins are highly bound to plasma proteins. Oxacillin has a very narrow spectrum and is used primarily as an antistaphylococcal agent. 