Screening for betalactam resistance* using Cefadroxil 30 µg disk

SRGA breakpoints on ISA (Oxoid), semiconfluent inoculum, 18-20 h incubation, 36 C, ambient air:
The following breakpoints valid for E.coli, Klebsiella pneumoniae, Klebsiella oxytoca and Proteus mirabilis:
ESBL-screen negative >14 mm; ESBL-screen positive zone diameter <13 mm
Breakpoints for Citrobacter spp are 10/9 mm.

*Cefadroxil indiscriminately picks up ESBL-, AmpC- and OXY-enzymes.
Further testing is needed to differentiate between the various enzymes.