Enterobacter sakazakii is an opportunistic pathogen that can cause meningitis, necrotising enterocolitis, bacteraemia and sepsis in infants (Mullane et al., 2007). It was first designated as a novel species in 1980 by Farmer et al. and several outbreaks in neonatal intensive care units have been linked to contamination of powdered infant formula (Lai, 2001; van Acker et al., 2001; Himelright et al., 2002). The organism is therefore of concern to infant food manufacturers as well as clinical microbiologists and food safety regulators (Anon., 2004, 2006a).

In 2007 the taxonomy of E. sakazakii was updated using a polyphasic approach based on extensive geno- and phenotypic evaluations (Iversen et al., 2007a). This resulted in the description of five novel species and the proposal that these be incorporated into a new genus, Cronobacter (Iversen et al., 2008a). The novel genus is contaxic with E. sakazakii and comprises Cronobacter sakazakii, C. malonaticus, C. turicensis, C. dublinensis, C. muytjensii and the unnamed genomospecies 1. Multi-locus sequence analysis (MLSA) of the family Enterobacteriaceae also supports the classification of these organisms as a distinct genus (Kuhnert et al., 2009). All the named species of Cronobacter contain clinical isolates and should be considered pathogenic.