Table 1.

Criteria of positivity of the phenotypic tests used to detect ESBL and AmpC enzymes.

Test	ESBL detection	AmpC detection
mDDST*	Extension of the inhibition zone towards the disk with the inhibitor and/or enlargement of the zone by more than 5 mm around the disk with the inhibitor (Figure 1)
mAmpC test**		Enlargement of the inhibition zone by more than 5 mm as compared with the disk without 3-aminophenylboronic acid (Figure 2)
mMIC***	Cefoxitin MIC ≤16 mg/L and a ratio of MIC of cefoperazone and cefoperazone/sulbactam >2:1	Cefoxitin MIC ≥16 mg/L and a ratio of MIC of cefotaxime and cefotaxime/3-aminophenylboronic acid or MIC of ceftazidime and ceftazidime/3-aminophenylboronic acid >2:1
ESBL Etest	At least 4-fold decrease of MIC of the particular third- or fourth-generation cephalosporin (cefotaxime and ceftazidime in case of E. coli and K. pneumoniae, and in addition cefepime in S. marcescens) in the presence of the inhibitor (cefotaxime/clavulanic acid and ceftazidime/clavulanic acid, and additionally cefepime/clavulanic acid in S. marcescens) (Figure 3)

^*Modified double-disk synergy test;

^**modified AmpC disk method;

^***modified microdilution method.