Quality control limits for teicoplanin susceptibility tests and confirmation of disk diffusion interpretive criteria

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Abstract
For monitoring the performance of teicoplanin susceptibility tests, the following quality control limits are recommended: Staphylococcus aureus ATCC 29213, MIC of 0.12 to 0.5 .mu.g/ml; Enterococcus faecalis ATCC 29212, MIC of 0.06 to 0.25 .mu.g/ml; and S. aureus ATCC 25923, zones 15 to 19 mm in diameter (30-.mu.g disks). However, some lots of Mueller-Hinton agar provided unusually large zones of inhibition with both vancomycin and teicoplanin disks, and these lots should be excluded before routine use. Teicoplanin and vancomycin differed only in their activity against oxacillin-resistant strains of Staphylococcus haemolyticus, which had decreased susceptibility to teicoplanin but were fully susceptible to vancomycin. For tests with 30-.mu.g teicoplanin disks, zones .ltoreq. 10 and .gtoreq. 14 mm in diameter represent resistant and susceptible breakpoints, respectively.