title: The relationship of disc position to zone-of-inhibition size in the disc-agar diffusion test.
abstract: One hundred sixteen clinical isolates of Enterobacter sp., Escherichia coli, Klebsiella sp., Proteus mirabilis, Staphylococcus aureus and S. epidermidis were tested against cefoperazone, cefoxitin, cefamandole and piperacillin by disc-agar diffusion. Zones-of-inhibition of discs dropped near the center of the plate were compared with those dropped near the periphery. In 28% of the comparisons the inner and outer zones differed by 2 mm or more. Of those, the inner zone was larger 2.5 times more often than the outer zone. Results suggest that the chances of obtaining a susceptible result are greater when discs are placed near the center as opposed to the periphery of the plate.
mesh_terms: D000362:Agar; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000254:growth & development; D004058:Diffusion; D008826:Microbial Sensitivity Tests
chemical_list: D000900:Anti-Bacterial Agents; D000362:Agar