Educational resource · Not a medical device · Infectious diseases review in progress · Does not replace clinical judgement

Diagram — The four resistance mechanisms — SeptiMap

name the four antibiotic resistance mechanisms, one example of each, and their genetic basis. Educational resource, not a medical device.

Diagrams: mechanisms and principles

17 sourced diagrams · for medical students and practice

Each diagram reads step by step: an objective, the steps, three key points, a classic pitfall, its sources and the related atlas pages. Revision mode hides the labels to test yourself.

Clinical years · residency

The four resistance mechanisms

Objective: name the four antibiotic resistance mechanisms, one example of each, and their genetic basis.

Step 5 / 5
The four resistance mechanisms1. Enzymatic inactivation — Enzymes destroy or modify the antibiotic: β-lactamases (including ESBLs and carbapenemases), aminoglycoside-modifying enzymes. 2. Altered target — PBP2a encoded by mecA in MRSA; van genes (D-Ala-D-Lac) in vancomycin-resistant enterococci; topoisomerase mutations (fluoroquinolones). 3. Reduced permeability — In Gram-negatives, loss or alteration of porins limits antibiotic entry. 4. Active efflux — Pumps (for example RND in P. aeruginosa) expel the antibiotic, often several classes at once. 5. Genetic basis — Chromosomal mutation, or gene acquisition by horizontal transfer (plasmids, transposons, integrons); the KPC carbapenemase is plasmid-borne.11Enzymatic inactivationβ-lactamases, ESBLs, carbapenemases22Altered targetPBP2a (mecA), van, topoisomerases33Reduced permeabilityporin loss (Gram-negatives)44Active effluxpumps, often multidrug55Genetic basismutation; plasmids, transposons
  • Pathogen
  • Antibiotic
  • Toxin, damage
  • Immunity

Key points

  • Four mechanisms: enzyme, altered target, reduced permeability, efflux.
  • MRSA: PBP2a (mecA); VRE: van; KPC: plasmid-borne carbapenemase.
  • Mutation, or a gene acquired by horizontal transfer.

Classic pitfall

Reducing resistance to “one enzyme”: mechanisms add up (porin, efflux, enzyme).

Related pathogen pages (9)

Sources

Educational content · Illustrative mechanisms · Not applicable to individual clinical decisions · MDR 2017/745

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