TABLE 2

Results of the colorimetric assays applied in a routine microbiology laboratory

β-Lactamase class and identification(s) (no. of isolates)aBacterial species identificationResistance to meropenembColorimetric assay results
Pure cultureBlood culture
CNPt-DirectBlue-CarbaCNPt-DirectBlue-Carba
Class A carbapenemases
    KPC (27)Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
Klebsiella pneumoniae+++++
    GES (1)Serratia marcescens+
Class B carbapenemase
    NDM (1)Klebsiella pneumoniae+++++
Carbapenemase coproducers
    KPC + NDM (1)Escherichia coli+++
Negative for carbapenemases tested (3)Klebsiella pneumoniae+
Klebsiella pneumoniae+
Escherichia coli+
All negative (281)
  • a Carbapenemases genes were investigated by real-time polymerase chain reaction-high resolution melting (RT-PCR-HRM) for the following genes: blaNDM-1, blaKPC, blaOXA-48-like, blaGES, and blaIMP.

  • b Resistance to meropenem was evaluated in the antibiogram of the conventional protocol.