Diffusion of teicoplanin and vancomycin in agar.

Teicoplanin, although more active than vancomycin [by minimum inhibitory concentration (MIC)], produces smaller inhibition zones in sensitivity testing with 30-microgram disks. Our data support the hypothesis that this is due to lower diffusion of teicoplanin in agar media. After 6 hr of incubation, approximately 70% of vancomycin, but only 20% of teicoplanin entered the agar from a paper disk charged with 30 micrograms of antibiotic.