Table 1.

MICs for bla IMP-4-positive isolates of Acinetobacter spp.

Isolate type and lab no.SampleDNA groupDate isolated (mo/yr)β-Lactamase pI(s)MIC (μg/ml)a
IMPMEMATMPIPTZPCTXSUL
Isolates from which bla IMP-4was sequenced
 116665Blood210/945.40.50.2516>12832>12816
 127091Blood29/967.6, 8.0b 161664>12864>1284
 74510Wound13TU5/955.7, 7.6, 8.0b >32>3232>12832>12816
 104680Blood38/985.7, 7.6, 8.0b 81632>12864>1281
Collection of 23 bla IMP-4 positive isolates
 MIC range0.25–160.25–162–6464–2564–6432–2561–64
 MIC50 c 4832256321282
 MIC90 d 1616642566425616
  • a ATM, aztreonam; CTX, cefotaxime; IMP, imipenem; MEM, meropenem; PIP, piperacillin; SUL, sulbactam; TZP, piperacillin-tazobactam (tazobactam at 4 μg/ml).

  • b Enzymes with pIs of 8.0 ceased to be detectable if the gel was overlaid with 3 mM EDTA for 10 min before addition of nitrocefin.

  • c MIC50, MIC at which 50% of isolates are inhibited.

  • d MIC90, MIC at which 90% of isolates are inhibited.