Gram negative organisms historically referred to as "SPICEM" organisms:
Serratia spp.
Providencia spp.
Citrobacter freundii (not applicable to other Citrobacter)
Enterobacter spp.
Morganella morganii
Primary therapeutic concern with AmpC is induction/de-repression of beta-lactamase enzyme with exposure to beta-lactams.
This can confer resistance to third generation cephalosporins and some beta-lactam/beta-lactamase inhibitors, leading to treatment failure with these antimicrobials.
Most AmpC organisms are healthcare-associated. They are Enterobacteriaceae that are part of the GI flora.
ESBLs vs. ampC: Most ESBLs are plasmid-encoded beta-lactamases, whereas ampCs are usually inducible and chromosomal beta-lactamases.
