. 2019 Aug 7;34(1):114. doi: 10.4102/sajid.v34i1.114

TABLE 1-A1.

Analysis of discrepant results for extended-spectrum beta-lactamase detection.

Organism	Isolate	Resistance phenotype and susceptibility profile^† according to Vitek 2	ESBL detection by disc diffusion	ESBL detection by Sensititre MIC	Dual phenotypic methods	CTX-M detected by PCR	CTX-M plus either phenotypic method	ESBL detection by composite reference standard
E. coli	8	Acquired penicillinase Non-susceptible to ampicillin, co-amoxiclav, cefuroxime Susceptible to cefotaxime, ceftazidime, cefepime, cefoxitin	- Susceptible to cefotaxime and ceftazidime	+^§ Susceptible to cefotaxime and ceftazidime	-	+	+	+
E. coli	9	Acquired penicillinase Non-susceptible to ampicillin, co-amoxiclav, cefuroxime Susceptible to cefotaxime, ceftazidime, cefepime, cefoxitin	- Susceptible to cefotaxime and ceftazidime	+^¶ Susceptible to cefotaxime Non-susceptible to ceftazidime	-	+	+	+
E. coli	10	Acquired penicillinase Non-susceptible to ampicillin, co-amoxiclav, cefuroxime Susceptible to cefotaxime, ceftazidime, cefepime, cefoxitin	+^‡ Non-susceptible to cefotaxime Susceptible to ceftazidime	+^†† Susceptible to cefotaxime and ceftazidime	+	+	+	+
Klebsiella pneumoniae	67	ESBL or SHV hyper-producer	-	+	-	-	-	-

^†

, According to CLSI criteria.

^‡

, Cefotaxime zone diameter (mm): cefotaxime + clavulanic acid zone diameter (mm) = 22:32, that is, ESBL-positive; ceftazidime zone diameter (mm): ceftazidime + clavulanic acid zone diameter (mm) = 26:27, that is, ESBL negative.

^§

, Cefotaxime MIC (µg/mL): cefotaxime + clavulanic acid MIC (µg/mL) = 1: ≤ 0.12/4, that is, ESBL-positive; ceftazidime MIC (µg/mL): ceftazidime + clavulanic acid MIC (µg/mL) = 0.5: ≤ 0.12/4, that is, indeterminate.

^¶

, Cefotaxime MIC (µg/mL): cefotaxime + clavulanic acid MIC (µg/mL) = 0.5: ≤ 0.12/4, that is, indeterminate; ceftazidime MIC (µg/mL): ceftazidime + clavulanic acid MIC (µg/mL) = 16: 0.5/4, that is, ESBL-positive.

^††