THE ROLE OF THE TYPHOID COLONIZATION FACTOR (TCF) IN THE VIRULENCE OF NON TYPHOIDIAL SEROVARS

Salmonella enterica serovar Typhi is a human-restricted pathogen and the causative agent of enteric fever disease. The typhoid colonization factor (Tcf) is a fimbrial apparatus, which is secreted via the chaperone-usher pathway and was suggested to play a role in S.Typhi host-specificity. The tcf operon includes four genes: tcfABCD followed by two additional ORFs with unknown function (tinR and tioA). Although Tcf is considered to be a typhoid virulence factor, pervious work in our lab demonstrated that the tcf operon is present in clinical isolates of non-typhoidal Salmonella (NTS) from serovars Schwarzengrund, 9,12:l,v:- , Choleraesuis, Heidelberg, Montevideo and Virchow. This entire region also found to be horizontally transferred and integrated between the genes sinR and pagN in genome of these pathogens.
To characterize the role of the tcf operon in the virulence of NTS, we created an in-frame deletion of the tcf region in S. Schwarzengwound and S. Infantis and studied its role in host cells adhesion and invasion.
We showed that the absence of the Tcf region from S. Schwarzengwound significantly reduces host cells invasion, but does not affect adhesion. Interestingly, a deletion of the tcf operon in S. Infantis resulted in an increase of adhesion and invasion relative to the wild type background.
Furthermore, the expression of the tcf operon under different growth conditions, intracellular replication, biofilm formation and motility were also studied. Collectively, our results showed the presence of the tcf in several NTS serovarsand established that this factor is playing a role in their virulence.