TABLE 1.

Differentiation of Cronobacter spp. using phenotypic and genotypic tests

SpeciesNo. of isolates% Positive strains by assay% Strains identified as a match by biochemical galleryc
α-Glucosidase substrateaChromogenic agarbgluA PCRdnaG reverse transcriptase PCR
4-NP-α-Glc4-MU-α-GlcX-α-GlcAMGESIADFIAESPMFullShortAPI20EID32E v3.0
C. sakazakii18510010010099959699.51001001006689
C. turicensis8100100100100100100100100100100100100
C. muytjensii71001001000100100100100100100100100
Cronobacter dublinensis810010010010010087.5100100100100100100
Cronobacter” genomospecies 12100100100100100100100100100100100100
All “Cronobacter” spp.2101001001009695.796.299.51001001007090
Other Enterobacteriaceae (after ESSP)1023546323724.5 (7)d32.4 (8)d38.2 (11)d00070
  • a Substrate assays were for yellow pigment (4-NP-α-Glc), fluorescence (4-MU-α-Glc), blue-green pigment (X-α-Glc), and acid production (AMG).

  • b Chromogenic agar assays were for blue-green colonies (ESIA and DFIA), blue-black or blue-gray colonies (ESPM), and fermentation of sucrose and melibiose (ESSP).

  • c Percent strains identified as a good to excellent match with E. sakazakii.

  • d Value in parentheses is the new percent positive after screening for sucrose and melibiose fermentation; values for Cronobacter isolates remain unchanged.