Cefixime disk susceptibility test criteria

A total of 583 bacterial isolates was tested for susceptibility to cefixime by broth microdilution and by disk agar diffusion with 5-, 10-, and 30-microgram disks. At MIC breakpoints of less than or equal to 1.0 and greater than or equal to 4 micrograms/ml for susceptible and resistant, respectively, the 5-microgram disk showed slightly better discrimination. The 5-microgram cefixime disk is recommended with proposed interpretive breakpoint criteria of: less than or equal to 17 mm, resistant; 18 to 20 mm, intermediate; and greater than or equal to 21 mm, susceptible.