Species identification of Cronobacter spp.based on recN gene

Objective To establish a method for species identification of Cronobacter spp.based on recombination and repair protein gene(recN),and to identify Cronobacter strains isolated from different sources at species level by the method established.Methods The whole recN genes of 8 Cronobacter reference strains were amplified and sequenced.Different fragments of recN gene were selected according to their length and location.After comparison and analysis of the phylogenetic tree with MEGA 4.0,a credible and shorter renN gene sequence was chosen for species identification,and then 44 Cronobacter isolates and 8 reference strains were identified at species level and the results were proved by bioochemical reactions.Results Cronobacter strains can be identified at species level based on 640 bp gene sequence of recN.The location of 8 reference strains in the dendrogram was used as a reference according to the genetic distance.All the 44 Cronobacter isolates were identified at species level,including 37 strains of Cronobacter sakazakii,3 strains of Cronobacter malonaticus,3 strains of Cronobacter turicensis,and 1 strain of Cronobacter universalis.The results were coincident with biochemical reaction results.Conclusion The established method could be adopted to identify Cronobacter spp. species by one sequencing after PCR amplification,and it is simple and rapid compared with biochemical identification and the method based on the whole recN gene.