Fig. 1.

Immunoflorescence staining to visualize expression of the z66 and d S. Typhi flagellar antigens. A. Confocal microscopy image of 404ty-fliC(d) (pre-phase change) expressing the z66 flagellar antigen. The bacterial cell post incubation with anti-z66 antibody is stained blue (DAPI nuclear stain) and the z66 flagellar antigen is stained green. Scale is estimated by magnification. B. Image of 404ty-fliC(d) (pre-phase change) post incubation with an anti-d flagellar antibody (red) and nuclear stained with DAPI (blue). C. Confocal microscopy image of 404tya-fliC(d) (post-phase change). Bacterial cell is stained as A. The magnification has been decreased with respect to A to demonstrate that S. Typhi cells expressing the z66 antigen could not be detected after undergoing phase change. D. Image of 404tya-fliC(d) (post-phase change), the bacterial cell is stained as in C.