DSSSB 12 August 2024
Pharmacology
Easy
What is the drug of choice for Methicillin Staphylococcus aureus (MRSA)?
Appeared in: DSSSB 12 August 2024
Explanation
- Vancomycin is a glycopeptide antibiotic and is the established drug of choice for treating serious or invasive infections caused by MRSA.
- MRSA is resistant to all beta-lactam antibiotics (like penicillins and cephalosporins) because it possesses the mecA gene, which produces an altered penicillin-binding protein (PBP2a).
- Vancomycin bypasses this resistance mechanism by inhibiting bacterial cell wall synthesis at a different target site, making it effective where beta-lactams fail.
Why Other Options Were Wrong
- Option A: Augmentin is a combination of amoxicillin (a penicillin) and clavulanic acid (a beta-lactamase inhibitor). MRSA's resistance is not due to beta-lactamase enzymes but an altered target site (PBP2a), making Augmentin ineffective.
- Option C: Azithromycin is a macrolide antibiotic. It is not a first-line treatment for MRSA due to high rates of resistance and because it is generally bacteriostatic, whereas a bactericidal agent is preferred for serious infections.
- Option D: Amoxicillin is a penicillin-class antibiotic. The 'M' in MRSA stands for Methicillin-resistant, which confers resistance to virtually all penicillin and cephalosporin antibiotics, including amoxicillin.
Related Visual
Clinical Relevance
- Nursing practice connection: Knowing Pharmacological management of Methicillin-Resistant Staphylococcus aureus (MRSA) helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
- Recognizing that Vancomycin is the drug of choice for MRSA is critical for patient safety, as using an ineffective antibiotic like a penicillin can lead to treatment failure, sepsis, and death.
- Nurses must administer Vancomycin via slow IV infusion (over at least 60-90 minutes) to prevent Red Man Syndrome, a common and distressing infusion-related reaction.
- Therapeutic drug monitoring of vancomycin trough levels is a key nursing responsibility to ensure efficacy while preventing dose-related toxicities like kidney damage (nephrotoxicity) and hearing loss (ototoxicity).
How to Approach the Question
- First, identify the key pathogen in the question: 'Methicillin-Resistant Staphylococcus aureus (MRSA)'.
- Recall the meaning of 'Methicillin-Resistant'. This signifies that the bacterium is resistant to all beta-lactam antibiotics, which includes the entire penicillin and cephalosporin families.
- Examine the options and eliminate any beta-lactam antibiotics. 'Augmentin' (amoxicillin/clavulanate) and 'Amoxycillin' are both penicillin-based drugs and are therefore ineffective.
- Consider the remaining options. 'Azithromycin' is a macrolide, which has high rates of MRSA resistance and is not a primary choice.
- This leaves 'Vancomycin', a glycopeptide antibiotic, which is the well-established gold standard for treating serious MRSA infections. Select this as the correct answer.
Concept Tested & Keywords
- Concept Tested: Pharmacological management of Methicillin-Resistant Staphylococcus aureus (MRSA).
- Stem keywords: Methicillin Staphylococcus aureus, MRSA, drug of choice
- Lead-in keywords: What is
- Negative lead-in flag: false
Question ID
QdjojCQf0WUTqNCzoA6i0S
Reference Book
E6 Microbiology Essentials Sastry 4e Part 2 p. 70-72
E6 Medicine Harrison 22e Part 1 p. 1245-1247
Practise the full DSSSB 12 August 2024
Attempt every question from this paper in a timed mock, then review the full solution for each one.
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