boulevard des Prairies, Laval, Qué bec H7V 1B7, Canada tcf (Typhi colonization factor) is one of the 12 putative chaperone/usher fimbrial clusters present in the Salmonella enterica serovar Typhi genome. We investigated the production, expression and regulation of tcf as well as its role during interaction with human cells. The tcf gene cluster was cloned and induced in Escherichia coli and S. Typhi, and the production of intertwined fibres similar to the Cbl (cable) pili of Burkholderia cepacia was observed on the bacterial surface by electron microscopy. In S. Typhi, tcf was expressed more after growth in M63 minimal medium than in standard Luria-Bertani medium. Analysis of the promoter region identified putative binding sites for the global regulators RcsB, ArgR and Fur. The expression of tcf was measured in isogenic strains lacking these global regulators. Under the conditions tested, the results showed that tcf expression was higher in the fur mutant and was regulated by iron concentration. Fur may regulate these fimbriae indirectly via the small RNAs RyhB1 and RyhB2. An isogenic mutant harbouring a deletion of the tcf cluster did not demonstrate any defect in adhesion or invasion of human epithelial cells, or in phagocytosis or survival in macrophages, when compared to the WT serovar Typhi strain. However, the tcf cluster contributed to adherence to human epithelial cells when introduced into E. coli. Thus, tcf genes encode functional fimbriae that can act as an adhesin and may contribute to colonization during typhoid fever.

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Immunization of cattle with the bacillus Calmette-Guérin (BCG) vaccine, especially neonates, induces protection against Mycobacterium bovis (M. bovis) and has been proposed as a strategy for bovine tuberculosis (bTB) control. Therefore, the aim of this study was to evaluate the immune response induced under field conditions in neonatal calves vaccinated with BCG Phipps, a strain that has rarely been evaluated in the bovine population, using interferon (IFN)-γ and tuberculin tests, flow cytometry and enzyme-linked immunosorbent assay. Two groups (vaccinated and control) of 5 calves were monitored for 12 weeks, and increases in the in vitro IFN-γ production, the percentage of cluster of differentiation (CD)8 + T cells and the activation levels of CD4 + and CD8 + T cells were observed 3 to 4 weeks post-vaccination. Bovine purified protein derivative-specific IFN-γ production was increased about 4.8-and 5.5-fold in vaccinated animals compared to non-vaccinated animals 3 and 4 weeks post-vaccination respectively. CD8 + T cells of the vaccinated group were increased 1.6-, 1.5-and 1.6-fold at weeks 2, 3 and 4 respectively. Levels of activation were 1.7-and 1.9-fold higher for CD4 + T cells and 2.3-and 1.8-fold higher for CD8 + T cells in the vaccinated group at weeks 3 and 4 respectively in response to M. bovis antigens. However, no animals (vaccinated or control) showed positive results for the single intradermal comparative tuberculin test (SICTT). Therefore, our results indicate that vaccination with M.bovis BCG Phipps strain stimulated peripheral blood T cell activity and induced a cell-mediated immune response. In addition, vaccination did not interfere with the SICTT, as previously reported, which indicates that this vaccine could be successfully applied in bTB control campaigns.