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?
**Core Concept**
The patient has a beta-lactamase-positive staphylococcal strain, which implies resistance to penicillin due to the production of beta-lactamase enzymes that hydrolyze the beta-lactam ring of penicillin, rendering it ineffective. Therefore, an alternative antibiotic that is not susceptible to beta-lactamase degradation is required.
**Why the Correct Answer is Right**
Oxacillin is a beta-lactamase-resistant penicillin, which means it can still be effective against beta-lactamase-producing bacteria like the staphylococcal strain in this patient. Oxacillin works by inhibiting cell wall synthesis in bacteria, ultimately leading to cell lysis and death. Its resistance to beta-lactamase degradation makes it an ideal choice for treating infections caused by beta-lactamase-producing bacteria.
**Why Each Wrong Option is Incorrect**
**Option A:** Ampicillin is a beta-lactam antibiotic that is susceptible to beta-lactamase degradation, making it ineffective against beta-lactamase-positive bacteria.
**Option C:** Ticarcillin is a carboxypenicillin that is also susceptible to beta-lactamase degradation, although to a lesser extent than ampicillin.
**Option D:** Penicillin G is a narrow-spectrum beta-lactam antibiotic that is susceptible to beta-lactamase degradation, making it ineffective against beta-lactamase-positive bacteria.
**Clinical Pearl / High-Yield Fact**
When treating infections caused by beta-lactamase-producing bacteria, it's essential to choose an antibiotic that is resistant to beta-lactamase degradation, such as oxacillin, nafcillin, or methicillin. This is critical to prevent treatment failure and the emergence of resistant bacterial strains.
**✓ Correct Answer: B. Oxacillin**