Mechanisms of antimicrobial resistance

At a glance

• Bacteria resist antibiotics in five ways: destroy the drug (enzymes), alter the target, keep it out (porin loss), pump it out (efflux), or bypass the target.
• Resistance is intrinsic (a property of the species) or acquired, by chromosomal mutation or by horizontal gene transfer of plasmids, transposons and integrons.
• Plasmids often carry several resistance genes at once, so one antibiotic can select for resistance to many classes.