Fig. 5.

Coculture of various S. Typhi strains with A. castellanii for 21 days and pH of the cultures. (A) Growth of A. castellanii alone and in the presence of S. Typhi strain ISP1820, its isogenic phoP mutant (ISP1820 ΔphoP; involved in intracellular survival), and S. Typhi strain Ty2. (B) Growth of S. Typhi strain ISP1820 (squares), its isogenic mutant ISP1820 ΔphoP (triangles), and S. Typhi strain Ty2 (circles) with (solid lines) and without (dashed lines) A. castellanii. (C) pH value of culture medium containing only amoebae (square), only bacteria (triangle), or both microorganisms (circle). Values are the means ± standard errors of the means of at least two independent experiments. Asterisks indicate a significant difference (P < 0.05).