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Metaproteomics analyses as diagnostic tool for differentiation of Escherichia coli strains in outbreaks

The secreted proteins of the enterohemorrhagic and enteropathogenic E. coli (EHEC and EPEC) are the most common cause of hemorrhagic colitis, a bloody diarrhea with EHEC infection, which often can lead to life threatening hemolytic-uremic syndrome (HUS).We are employing a metaproteomic approach as an effective and complimentary technique to the current genomic based approaches. This metaproteomic approach will evaluate the secreted proteins associated with pathogenicity and utilize their signatures as differentiation biomarkers between EHEC and EPEC strains. The result showed that the identified tryptic peptides of the secreted proteins extracted from different EHEC and EPEC growths have difference in their amino acids sequences and could potentially utilized as biomarkers for the studied E. coli strains. Analysis of extract from EHEC O104:H4 resulted in identification of a multidrug efflux protein, which belongs to the family of fusion proteins that are responsible of cell transportation. Experimental peptides identified lies in the region of the HlyD haemolysin secretion protein-D that is responsible for transporting the haemolysin A toxin. Moreover, the taxonomic classification of EHEC O104:H4 showed closest match with E. coli E55989, which is in agreement with genomic sequencing studies that were done extensively on the mentioned strain. The taxonomic results showed strain level classification for the studied strains and distinctive separation among the strains. Comparative proteomic calculations showed separation between EHEC O157:H7 and O104:H4 in replicate samples using cluster analysis. There are no reported studies addressing the characterization of secreted proteins in various enhanced growth media and utilizing them as biomarkers for strain differentiation. The results of FY-2012 are promising to pursue further experimentation to statistically validate the results and to further explore the impact of environmental conditions on the nature of the secreted biomarkers in various E. coli strains that are of public health concerns in various sectors.