Enterobacter sakazakii, a gram-negative bacillus, is a rare cause of bloodstream and central nervous system infections. In 2007, following extensive study, it was proposed that the original taxonomy of Enterobacter sakazakii be revised, to consist of five new species moved to a new genus, identified as "Cronobacter". (1) A review of the what, the how, and the why the change was first proposed, and why it was eventually approved, provides an insight into the related scientific process of taxonomy at work, involving this notorious neonatal pathogen.
Initially, taxonomy is the science of classifying organisms, identifying and naming species, and organizing them into systems of classification. At least 1.7 million species of living organisms have been discovered, and the list grows longer every year. Ideally, classification should be based on homology, i.e., the shared characteristics that have been inherited from a common ancestor. Until recent decades, the study of homologies was limited to anatomical structures and pattern of embryonic development. However, since the birth of molecular biology, homologies can now also be studied at the level of proteins and DNA. (2)