|SALEHI, SANAZ - Mississippi State University|
|HOWE, KEVIN - Mississippi State University|
|LAWRENCE, MARK - Mississippi State University|
|BAILEY, HARTFORD - Mississippi State University|
|KARSI, ATTILA - Mississippi State University|
Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2016
Publication Date: 1/1/2017
Publication URL: https://handle.nal.usda.gov/10113/5729160
Citation: Salehi, S., Howe, K., Lawrence, M.L., Brooks, J.P., Bailey, H.R., Karsi, A. 2017. Salmonella enterica Serovar Kentucky Flagella are Required for Broiler Skin Adhesion and Caco-2 Cell Invasion. Applied and Environmental Microbiology. 83(2):e02115-16.
Interpretive Summary: Determining the mechanism(s) involved in bacterial pathogen contamination on food still requires more investigation. For instance, the presence of Salmonella on chicken skin is difficult to understand, as the presence of one strain on the surface of chicken is not representative of the typical strain causing human disease. This suggests that chickens have a “preference” for Salmonella attachment and not all strains are alike. The purpose of this study was to determine the mechanism(s) involved in chicken skin attachment and determine the effect of “knocking” out the genes responsible for these mechanisms. Altered Salmonella were placed in a chicken skin attachment assay to determine if the knocked out gene was responsible for skin attachment. One specific gene was found to be responsible for much of the attachment to chicken skin and invasion of simulated human tissue surface. This work helps us understand the importance of specific mechanisms in facilitating pathogen transfer from farm to fork and possibly shed light on potential targets.
Technical Abstract: Non-typhoidal Salmonella are the main source of pathogenic bacterial contamination in the poultry industry. Recently, Salmonella enterica serovar Kentucky has been recognized as the most prominent serovar on carcasses in poultry processing plants. Previous studies showed that flagella are one of the main factors that contribute to bacterial attachment to broiler skin. However, the precise role of flagella and mechanism of attachment is unknown. There are two different flagella sub-units (fliC and fljB) expressed alternatively in Salmonella enterica serovars and allow bacterial phase variation. Here, by making several deletions in flagella structural sub-units flgK, fliC and fljB, and flagella motor force (motA), we were able to differentiate the role of flagella and its motility in colonization of broiler skin and cell culture. Utilizing a broiler skin assay, we demonstrated that the presence of the sub-unit fliC is necessary for bacterial attachment to the broiler skin. Although, the expression of the alternative flagella sub-unit fljB leaves the Salmonella motile, it is unable to make a tight attachment. Also, deletion of the flgK gene prevents proper flagella assembly, making Salmonella significantly less adherent to broiler skin compared to wild type. In addition, unflagellated strain of S. Kentucky with deletion in both fliC and fljB genes and flgK, as well as a flagellated but paralyzed mutant (motA) exhibited less adhesion and invasion characteristics to Caco-2 cells while the fljB mutant was as adherent and invasive as the wild type strain.