Gram negative organisms with beta-lactamase enzymes that confer resistance to 3rd generation cephalosporins in addition to lower order beta-lactams (eg, ampicillin).
Generally, ESBL refers to certain strains of E. coli, Klebsiella, and Proteus.
ESBL-producing organisms may be normal part of GI flora.
Elevated risk of ESBL if known prior colonization/infection, broad-spectrum antibiotic exposure within last 30 days, travel to endemic areas within last 30 days.
Asymptomatic colonization, or any syndrome caused by the organism carrying it (see the organism for list)
ESBLs vs. ampC: Most ESBLs are plasmid-encoded beta-lactamases, whereas ampCs are usually inducible and chromosomal beta-lactamases.