Table 2.

Abilities of antimicrobial susceptibility testing methods to detect decreased susceptibility to extended-spectrum cephalosporins and aztreonam

MethodNo. of laboratories using the methodNo. (%) of laboratories that reported at least one nonsusceptible result with an extended-spectrum cephalosporin or aztreonama for:
CT-6CT-7CT-8CT-9CT-10
MicroScan15b91111111c
Vitek13d9910100
Disk diffusion8e66560
Sensititre or in-house broth microdilution222220
 All methods3826 (68.4)28 (73.7)28 (73.7)29 (76.3)1 (2.6)
  • a Includes results of intermediate or resistant obtained with traditional (nonscreening) NCCLS breakpoints for ceftazidime, cefotaxime, ceftriaxone, or aztreonam.

  • b Includes four laboratories that did not test any extended-spectrum cephalosporins or aztreonam.

  • c One laboratory reported this organism as ceftazidime resistant.

  • d Includes two laboratories that tested ceftizoxime as the only extended-spectrum cephalosporin and did not test aztreonam.

  • e Includes two laboratories that did not test any extended-spectrum cephalosporins or aztreonam.