Comparative Outer Membrane Protein Analysis of High and Low-Invasive Strains of Cronobacter malonaticus.

Maha A Aldubyan,Fatiha M Benslimane,Stephen J Forsythe,Abdlrhman M Alsonosi,Ibtesam S Almami

doi:10.3389/fmicb.2017.02268

Maha A Aldubyan, Fatiha M Benslimane + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2017.02268

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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.

Highlights

Cronobacter species are Gram-negative, facultative anaerobic rod-shaped bacteria and are members of the Enterobacteriaceae family (Iversen et al, 2008)
In order to identify any differences in the outer membrane proteins (OMPs) profiles between the eight C. malonaticus strains, their OMPs were extracted and separated using 10% SDS-PAGE (Figure 1)
Most reported studies on Cronobacter have focused on C. sakazakii as it is well known with respect to outbreaks of severe infant infections in neonatal intensive care units

Summary

Introduction

Cronobacter species are Gram-negative, facultative anaerobic rod-shaped bacteria and are members of the Enterobacteriaceae family (Iversen et al, 2008). Cronobacter universalis, Cronobacter muytjensii, Cronobacter dublinensis, and Cronobacter condimenti (Cetinkaya et al, 2013). They occur in the environment, plant material and subsequently the ingredients of various foods (Forsythe et al, 2014). Cronobacter species have been isolated from a wide range of sources including food, rats, flies, and asymptomatic human carriage has been reported (Kandhai et al, 2004; Friedemann, 2007; Miled-Bennour et al, 2010). The organism has been isolated from the hospital environment and clinical samples, including cerebrospinal fluid, blood, bone marrow, sputum, urine, inflamed appendix, neonatal enteral feeding tubes, and conjunctivae (Iversen and Forsythe, 2003; Hurrell et al, 2009; Holy and Forsythe, 2014)

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