Phenotypic Confirmatory Test

The Phenotypic Confirmatory Test (PCT) is used to confirm the presence of an Extended-Spectrum Beta-Lactamase (ESBL) producing organism. The following antibiotics are used:


Antibiotic	Abbreviated Name	What to Report
Cefoxitin	CEF	Report diameter, and whether organism is Susceptible or Resistant depending on breakpoint (see below)
Ceftazidime	CAZ	Report diameter, and whether potentiation occurs between CAZ and CCA. > 5 mm difference is potentiation ≤ 5 mm difference is no potentiation
Ceftazidime + Clavulanic Acid	CCA
Cefotaxime	CTX	Report diameter, and whether potentiation occurs between CTX and CCT. > 5 mm difference is potentiation ≤ 5 mm difference is no potentiation
Cefotaxime + Clavulanic Acid	CCT

Cefoxitin Breakpoints:

≥ 18 mm Susceptible
15-17 mm Intermediate
≤ 14 mm Resistant