TABLE 3.

Summary of diagnostic criteria^a

β-Lactamase	Porin lossb	CAZ or CTXc	Clavulanic acid response	FOXd	APB response	IPMd	EDTA response
ESBL	−	P	Yese	S	No	S	No
	+	P	Yes	R	No	S	No
AmpC	−	P	No	R	Yes	S	No
	+	P	No	R	Nof	R/↓S	No
Carbapenemase class A	−	P	Yes	S	No	↓S	No
	+	P	Yes	R	No	↓S	No
Carbapenemase class B	−	P	No	R	No	↓S	Yes
	+	P	No	R	No	R	Yes

^aCAZ, ceftazidime; CTX, cefotaxime; FOX, cefoxitin; IPM, imipenem.

^bLoss of porins OmpK35 and OmpK36 in K. pneumoniae.

^cP, positive CLSI screening test result.

^dR, resistant; S, susceptible; ↓S, decreased susceptibility by CLSI disk interpretive criteria.

^eThe enhancement of the zone of inhibition was ≥5 mm.

^fFor AmpC, an APB response was seen with CAZ or CTX but not FOX.