Differential Protein Expression between Poor and Robust Colonizing Campylobacter jejuni Isolates

Introduction: Campylobacter jejuni is a leading cause of bacterial gastroenteritis in humans. Poultry is considered a major source of C. jejuni but colonization mechanisms in the chicken remain unclear.

Purpose: The purpose of this study was to determine colonization-associated factors of C. jejuni at the proteome level.

Methods: The proteomes of C. jejuni were quantitatively analyzed using trypsin catalyzed ¹⁶O/¹⁸O labeling in conjunction with two-dimensional liquid chromatography separation and tandem mass spectrometry analysis (2DLC-MS/MS).

Results: After oral challenge with 10⁵ CFU/ml of C. jejuni per chick, a poor colonizing isolate (A74/O) showed a 3 log reduction in the chick ceca relative to a robust colonizer (A74/C). C. jejuni recovered from birds were determined to be the same flaA SVR genotype as the original isolates. A total of 776 proteins were identified; 72 proteins (approximately 9.28% of the total proteins identified), were significantly changed (over 1.4-fold, P < 0.05) in the good colonizer. Surprisingly, only 4 of these proteins (RplL, CjaA, GlyS, and putative oxidoreductase subunit) were up-regulated, whereas the majority (68 proteins) were down-regulated. The differentially expressed proteins are primarily involved in cell motility, amino acid and lipid transport, post-translational modification, protein turnover, and chaperones. In addition, the robust colonizing isolate (A74/C) attached and invaded Caco-2 cells at significantly higher numbers than the poor colonizer (A74/O). Similarly, A74/C isolate rapidly translocated through differentiated Caco-2 monolayers compared to A74/O.

Significance: The present study clearly demonstrates the usefulness of proteomic profiles in the investigation of mechanisms that C. jejuni uses to occupy the poultry intestine and it could potentially be used for the vaccine development to reduce the threat of Campylobacter infection in chickens.