Article Figures & Data
Figures
- Fig. 1.
Comparison of the amino acid sequences of IMP-1, IMP-2, IMP-3, and IMP-4 β-lactamases. The 18 residues that comprise the IMP-1 signal peptide (21) are shaded.
Tables
- Table 1.
MICs for bla IMP-4-positive isolates of Acinetobacter spp.
Isolate type and lab no. Sample DNA group Date isolated (mo/yr) β-Lactamase pI(s) MIC (μg/ml)a IMP MEM ATM PIP TZP CTX SUL Isolates from which bla IMP-4was sequenced 116665 Blood 2 10/94 5.4 0.5 0.25 16 >128 32 >128 16 127091 Blood 2 9/96 7.6, 8.0b 16 16 64 >128 64 >128 4 74510 Wound 13TU 5/95 5.7, 7.6, 8.0b >32 >32 32 >128 32 >128 16 104680 Blood 3 8/98 5.7, 7.6, 8.0b 8 16 32 >128 64 >128 1 Collection of 23 bla IMP-4 positive isolates MIC range 0.25–16 0.25–16 2–64 64–256 4–64 32–256 1–64 MIC50 c 4 8 32 256 32 128 2 MIC90 d 16 16 64 256 64 256 16 ↵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.
- Table 2.
Kinetic properties of IMP-4 β-lactamase from isolate 74510
Substrate Relative Vmax(%)a Km (μM) Benzylpenicillin 100 365 Ampicillin 52 575 Piperacillin 8 144 Carbenicillin 62 1,000 Oxacillin 307 420 Cephaloridine 81 32 Cephalothin 111 71 Cefuroxime 46 52 Cefotaxime 9 18 Ceftazidime 7 28 Imipenem 53 42 Meropenem 8 12 Aztreonam 0.001 Not measured ↵a Based on a predicted molecular mass of 27,087 and a purity of 80%; based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, ak cat of 27.5 s−1 was estimated for IMP-4 against benzylpenicillin.
