TABLE 2.

Characteristics of KPC-producing Klebsiella pneumoniae isolates with low-, intermediate-, and high-level carbapenem resistance

Carbapenem resistance category and isolateaMIC (μg/ml) ofi:KPC variantWestern blot resultdGene dosagefTn4401 variable region
IPMMEMETP
Low
    ART2008226b<1<0.25<0.53+NAgNA
    ART2008142b<1483+0.62 ± 0.07No deletion
    AIS0810581422+0.05 ± 0.07No deletion
    AIS070654b4123+0.27 ± 0.02No deletion
    AIS081072b2283+0.35 ± 0.03No deletion
    AIS0808842483++0.49 ± 0.05No deletion
    ART2008140b4283++0.51 ± 0.01No deletion
    AIS070446b4443++0.64 ± 0.11No deletion
    HIP109244443++0.45 ± 0.01No deletion
    ART20080284883++0.52 ± 0.09No deletion
    ART2008137b48163+0.57 ± 0.04No deletion
Intermediate
    HIP14474b88163+0.48 ± 0.02No deletion
    ART2008136b88162+0.05h100-bp deletion
High
    ART2008022b816323++0.64 ± 0.01No deletion
    ART2008139b3216163+++++0.37 ± 0.1468-bp deletion
    ART2008143b816643++++0.38 ± 0.0268-bp deletion
    AIS080949b3216643++++2.03 ± 0.01No deletion
    HIP14358b3216642+++++0.12 ± 0.05100-bp deletion
    AIS080792b3232642+++++++0.55 ± 0.18100-bp deletion
    ART2008138b32321283++++0.28 ± 0.1968-bp deletion
    ART200802432641282+++++++0.18 ± 0.06255-bp deletion
    ART2008026b64642563++0.56 ± 0.29No deletion
    AIS081042b641282563+++++0.25 ± 0.09100-bp deletion
    AIS080571b1281282563++0.59 ± 0.13No deletion
    ART2008141b,c2562562563++0.47 ± 0.08No deletion
    ART2008135b,c5122561,0243++++1.81 ± 0.46No deletion
    ART2008027b,c5125121,0243++++e3.03 ± 0.29No deletion
  • a Isolates are arranged in order of increasing carbapenem resistance. Classification of isolates as having low-, intermediate-, and high-level carbapenem resistance was as defined in this study.

  • b Isolate that potentially lacks a functional OmpK35 porin (Table 3).

  • c Isolate that potentially lacks a functional OmpK36 porin (Table 3).

  • d KPC production is interpreted with plus signs to represent relative intensity of bands from the Western blot analysis (Fig. 2).

  • e The only result that varied between repeated Western blots as seen in Fig. 2.

  • f Gene dosage results are shown as a ratio of quantity of blaKPC (ng/μl) to that of rpoB (ng/μl).

  • g NA, not applicable because the isolate lost its blaKPC-carrying plasmid upon passage in vitro.

  • h blaKPCgene dosage result from only the first experimental repetition due to loss of the blaKPC-carrying plasmid prior to subsequent repetitions.

  • i IPM, imipenem; MEM, meropenem; ETP, ertapenem.