TABLE 1.

Stability of imipenem disks with 1,000 μg of EDTA added during storage as determined by change of inhibition zone diameter

Storage (wk)Diam (mm) of:
IMPb-EDTA disk zoneIMP disk zone, P. aeruginosa ATCC 27853a
IMP resistant, MBL positiveIMP resistant, MBL negativeP. aeruginosa ATCC 27853
P. aeruginosaA. baumanniiP. aeruginosaA. baumannii
4°C−20°C4°C−20°C4°C−20°C4°C−20°C4°C−20°C
Immediate2424232315151717242427
12323222312131515222324
42122222213131416212225
82021222313121515202125
122124232311131416202222
16202323251113915192225
241823222311121213192225
Mean21.022.922.423.112.313.013.715.320.722.324.7
  • a Routine quality control results with disks stored as recommended by the National Committee for Clinical Laboratory Standards. The acceptable imipenem disk zone diameter is 20 to 28 mm.

  • b IMP, imipenem.