Interpretive criteria for temocillin disk diffusion susceptibility testing

Abstract

The susceptibility of 677 clinical bacterial isolates to temocillin was determined by broth microdilution and disk diffusion methods for the purpose of evaluating disks with three different temocillin concentrations and determining the temocillin disk diffusion interpretive criteria. The 60μg temocillin disk provided the highest interpretive accuracy (96.2 %), although the 30μg disk differed by having only three (1.2 %) additional minor interpretive errors. Based on available temocillin pharmacokinetics and recommended dosage schedules, the minimum inhibitory concentration breakpoints chosen were: ⩾ 32μg/ml = resistant and ⩽ 16μg/ml = susceptible. The corresponding disk diffusion zone diameter breakpoints for the 60μg disk were ⩽ 17 mm and ⩾ 21 mm; zone diameters of 18–20 mm were considered intermediate. For the 30μg disk these were ⩽ 15 mm, ⩾ 19 mm and 16–18 mm respectively.