Table 1.

MICs and characteristics of β-lactamases produced byE. aerogenes

No. of strainsβ-Lactamase group (enzyme type)bEnzyme characteristicMIC (μg/ml) ofa:
pICTX hydrolysiscInhibited byd:InducibleeFOXCTXCAZATMFEPIMIGM
CLOXCLAV
118.3NoYesNoYes>256   1   4  1  0.12  0.5    8
2be (SHV-3)6.9YesNoYesNo
2918.3NoYesNoYes>256   1–2   8–32 32–64  0.12–1  0.5    1–16
2be (SHV-4)7.8YesNoYesNo
118.3NoYesNoYes>256   1–2  32 64  1  1>128
2be (SHV-5)8.0YesNoYesNo
41f (wild type)8.3–8.8NoYesNoYes ≥64 ≤1.0 ≤1.0≤0.5≤0.12≤0.5  ≤1.0
51f(derepressed)8.3–8.9YesYesNoNo>256≥32≥64 16–64≤1.0≤1.0    1–128
  • a FOX, cefoxitin; CTX, cefotaxime; CAZ, ceftazidime; ATM, aztreonam; FEP, cefepime; IMI, imipenem; GM, gentamicin.

  • b Based on Bush-Jacoby-Medeiros classification (5). The β-lactamase listed in parentheses is the one most similar to the group 2be enzyme produced by the Enterobacterstrains.

  • c Hydrolysis of 0.75 μg of cefotaxime (CTX) per ml used in substrate-based IEF overlay technique (1).

  • d Inhibitors used in IEF overlay technique were clavulanic acid (CLAV; 1,000 μM) and cloxacillin (CLOX; 1,000 μM) (28).

  • e Inducible by cefoxitin.

  • f Unpublished data from the Center for Research in Anti-Infectives and Biotechnology.