FIG 2.

Recommended scheme for determination of heteroresistance and interpretation criteria. Disc diffusion assays should be performed according to standardized procedures for antimicrobial susceptibility testing as recommended by agencies such as CLSI and BSAC. These procedures may be applied to Etest assays while taking into consideration the manufacturer's guidelines. PAP by CFU counts should be performed by plating aliquots of 10-fold serially diluted bacterial cultures on antibiotic-containing agar plates. Agar plate preparation should follow standardized guidelines for MIC determination by agar dilution assays. Turbidimetric PAP should follow standard guidelines for MIC determination by the broth dilution technique, with the exception of turbidimetric quantification of bacterial growth at each antibiotic concentration.