Reduction of ESBL/AmpC producing E. coli differed between slaughterhouses.
Chilled carcasses carried 102–105 CFU/carcass of ESBL/AmpC producing E. coli.
Both primary production and processing influenced levels after chilling.
E. coli can be used as surrogate for ESBL/AmpC producing E. coli through processing.
Improvements in processing hygiene can have a similar effect on multiple hazards.