The taxonomy of Enterobacter sakazakii: proposal of a new genus Cronobacter gen. nov. and descriptions of Cronobacter sakazakii comb. nov. Cronobacter sakazakii subsp. sakazakii, comb. nov., Cronobacter sakazakii subsp. malonaticus subsp. nov., Cronobacter turicensis sp. nov., Cronobacter muytjensii sp. nov., Cronobacter dublinensis sp. nov. and Cronobacter genomospecies 1

Abstract

Background: Enterobacter sakazakii is an opportunistic pathogen that can cause infections such as necrotizing enterocolitis, bacteraemia, meningitis and brain abscess/lesions. When the species was defined in 1980, 15 biogroups were described and it was suggested that these could represent multiple species. In this study the taxonomic relationship of strains described as E. sakazakii was further investigated.

Results: Strains identified as E. sakazakii were divided into separate groups on the basis of f-AFLP fingerprints, ribopatterns and full-length 16S rRNA gene sequences. DNA-DNA hybridizations revealed five genomospecies. The phenotypic profiles of the genomospecies were determined and biochemical markers identified.

Conclusion: This study clarifies the taxonomy of E. sakazakii and proposes a reclassification of these organisms.

Figure 1

16S rRNA gene phylogenetic tree of Cronobacter and related species. A Neighbor-Joining analysis was used with Felsenstein correction (1000 bootstrap replicates). The bar indicates 10% estimated sequence divergence.

Figure 2

f-AFLP dendogram of Cronobacter and related species. A DICE coefficient and UPGMA algorithm were used with an optimization of 0% and position tolerance of 0.2%. The scale bar represents the percentage of similarity.

Figure 3

Ribotype dendogram of Cronobacter and related species. A DICE coefficient and UPGMA algorithm were used with an optimization of 1% and position tolerance of 1.5%. The scale bar represents the percentage of similarity.