ARS | Publication request: Cell invasion of poultry-associated Salmonella Enteritidis isolates is associated with pathogenicity, motility and secretion of type-three secretion system secreted proteins

Submitted to: Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2011
Publication Date: February 2, 2011
Citation: Shah, D.H., Zhao, X., Addwebi, T., Davis, M., Orfe, L., Call, D., Guard, J.Y., Besser, T.E. 2011. Cell invasion of poultry-associated Salmonella Enteritidis isolates is associated with pathogenicity, motility and secretion of type-three secretion system secreted proteins. Microbiology. 157(5):1428-1445.

Interpretive Summary: Salmonella enterica serovar Enteritidis (S. Enteritidis) is a major cause of food-borne gastroenteritis in humans throughout the world. Poultry and poultry products are considered the major vehicles of transmission to humans. Using cell invasiveness as a surrogate marker for pathogenicity, we tested the invasiveness of fifty-three poultry-associated isolates of S. Enteritidis in well-differentiated intestinal epithelial cell model (Caco-2). The method allowed classification of isolates into low (n=7), medium (n=18) and high (n=30) invasiveness categories. The cell invasiveness of the isolates did not correlate with the presence of virulence associated gene, spvB, or their ability to form biofilms. Testing of representative isolates with high and low invasiveness in a mouse model revealed that former were also more invasive in vivo and caused more and earlier mortalities whereas latter were significantly less invasive in vivo, causing few or no mortalities. Further characterization of representative isolates with low and high invasiveness showed that most of the isolates with low invasiveness had impaired motility and impaired secretion of either flagella associated proteins (FlgK, FljB and FlgL) or type three secretion system (TTSS) secreted proteins (SipA and SipD) encoded on Salmonella pathogenicity island-1 (SPI-1). In addition, isolates with low invasiveness had impaired ability to invade and/or survive within chicken macrophages. These data suggest that not all isolates of S. Enteritidis recovered from poultry may be equally pathogenic, and that the pathogenicity of S. Enteritidis isolates is associated, in part, with both motility and secretion of TTSS effector proteins.

Technical Abstract: Salmonella Enteritidis is the world’s leading cause of human salmonellosis. It is primarily transmitted to people who consume eggs or egg products that are contaminated. The bacterium is unusual in that strains have little genetic variability, but nonetheless any one strain may have a high or low ability to cause egg contamination. It is important to have assays that can distinguish between strains that vary in their ability to cause disease so that genetic factors can be identified. Increased knowledge about how Salmonella Enteritidis evolves to associate with eggs helps to improve detection and prevention.