26/08/2025
🎯ESBL (Extended-Spectrum β-lactamase)
If the organism is E. coli that produces ESBL (Extended-Spectrum β-lactamase), then amoxicillin–clavulanic acid should NOT be reported as sensitive, even if the disk diffusion test shows a zone of inhibition. why ????
Because :
ESBL-producing organisms hydrolyze penicillins, cephalosporins, and aztreonam.
Amoxicillin–clavulanic acid may appear active in vitro because clavulanic acid inhibits some β-lactamase activity, leading to a false “sensitive” result.
However, in vivo (inside the patient), treatment failures are very common, since the ESBL enzymes can still overcome the antibiotic.
