Abstract
Cronobacter
are an important group of foodborne pathogens that has been linked to life-threatening infections in both infants and adults. The major infections associated with
Cronobacter
species are neonatal meningitis, necrotizing enterocolitis, and septicaemia. There are seven species in the
Cronobacter
genus, of which only three are of clinical importance;
Cronobacter sakazakii, Cronobacter malonaticus
, and
Cronobacter turicensis
. To date most studies have focussed on
C. sakazakii
as it is the major species associated with neonatal infections. However, recently
C. malonaticus
, in particular sequence type 7 (ST7), has been noted as being prevalent in adult infections and therefore warranting further investigation. In this study, eight strains of
C. malonaticus
ST7, that had been isolated from a wide range of sources and varied in their
in vitro
virulence, were chosen for proteomic analysis of their outer membrane proteins (OMPs). One-dimensional gel analysis revealed a ~29 kDa size band that was only present in the highly invasive strains. Subsequent mass spectrometric analysis identified several peptides that matched the flagellin protein. The presence of flagellin protein was confirmed in 2D gel spot. Mass spectrometry analysis of total OMPs revealed that the four highly invasive
C. malonaticus
strains expressed the main flagellum proteins that were absent from the four low invasive strains. These were the flagellar hook protein FlgE, flagellar hook-associated protein 1, flagellar hook-associated protein, flagellin, and flagellar hook-filament junction protein FlgL. This data indicates that
C. malonaticus
flagellar proteins may have an important role in the organism's invasion properties.