Enzymatic resistance mechanisms — drug modification/degradation: Resistance to antibiotics can arise via enzymes that chemically modify or hydrolyze the active drug. Which listed drug classes have well-known enzyme-mediated resistance pathways?

Introduction / Context:
Antibiotic resistance frequently involves enzymes that neutralize drug activity. Understanding these mechanisms informs antibiotic selection, β-lactamase inhibitor use, and stewardship strategies.

Given Data / Assumptions:

• We are comparing three classic enzyme-based resistance patterns.
• Bacteria can acquire chromosomal or plasmid genes encoding these enzymes.
• Selection pressure from antibiotic use promotes their spread.

Concept / Approach:
Penicillins are hydrolyzed by β-lactamases that open the β-lactam ring. Chloramphenicol is inactivated by chloramphenicol acetyltransferase (CAT), which acetylates the drug and prevents ribosomal binding. Aminoglycosides are modified by aminoglycoside-modifying enzymes (acetyltransferases, nucleotidyltransferases, phosphotransferases), reducing affinity for the 30S ribosome.

Step-by-Step Solution:
Match each class to its prototypical enzyme: β-lactamase → penicillins; CAT → chloramphenicol; AAT/ANT/APH → aminoglycosides.Recognize that all three are validated resistance pathways.Select the inclusive answer ‘‘All of these’’.

Verification / Alternative check:
Clinical use of β-lactamase inhibitors (clavulanate, tazobactam) and enzyme-stable agents (oxacillin, carbapenems) corroborates these mechanisms. Laboratory detection includes phenotypic tests and gene assays (e.g., bla, cat, aac/ant/aph).

Why Other Options Are Wrong:
Trimethoprim only is incorrect; resistance to trimethoprim commonly involves altered dihydrofolate reductase, not drug-modifying enzymes.

Common Pitfalls:
Assuming a single resistance route per class; multiple mechanisms may coexist (e.g., efflux, target changes, permeability defects).

Final Answer:
All of these.