Antibiotic Resistance Matcher

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Reference: Common Antibiotic Resistance Mechanisms

Type of Resistance	Example Mechanism	Example Antibiotics Affected
Increased Drug Efflux	New membrane transport system	Tetracyclines, Fluoroquinolones
Drug-Inactivating Enzyme	Beta-lactamase	Penicillins, Cephalosporins
	Acetyltransferase	Aminoglycosides
Decreased Drug Uptake	Mutated porin protein	Penicillins, Fluoroquinolones
Modified Drug Target	Altered penicillin-binding protein (PBP)	Penicillins (e.g., MRSA)
	Altered ribosomal protein	Aminoglycosides, Macrolides
	Altered DNA gyrase	Fluoroquinolones

💡 USMLE Step 1 Tips

• MRSA Context: The "Altered penicillin-binding protein" is a high-yield concept. Specifically, MRSA gains resistance to methicillin via the mecA gene, which encodes for PBP2a.
• Aminoglycosides: Note that Aminoglycosides appear twice: they can be resisted via enzymes (Acetyltransferase) or target modification (Ribosomal protein). The enzymatic modification (Transferases) is the most common mechanism of resistance for Aminoglycosides.
• Fluoroquinolones: These also appear frequently. Remember that DNA Gyrase is the same as Topoisomerase II.

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