[en] Objective: To study the relationship between S. typhi R plasmid (pR_ST98) and macrophage apoptosis. Methods: pR_ST98 was transferred into a less virulent strain of S. typhimurium for creating a transconjugant pR_ST98/RIA, the standard S. typhimurium virulence strain SR-11 was used as the positive control, and RIA as the negative one. Infection with murine macrophage J_774A.1 occurred separately under the same conditions. J_774A.1 apoptosis was detected by flow cytometry and TUNEL at 0, 2, 4, 6, 12, 24 hours respectively. Mitochondria membrane potential was detected by JC-1 staining method. Viable bacteria was detected by serial dilution at the same time and viable cells stained with Trypan blue were counted. Results: SR-11 results in a higher apoptosis in J_774A.1 than pR_ST98/RIA, and a combined pR_ST98/RIA higher than RIA (P<0.05 or 0.01). Viable bacteria and cells were RIA>pR_ST98/RIA>SR-11 (P<0.05 or 0.01). Conclusions: The bacteria carried plasmid pR_ST98 could increase the macrophage apoptosis. (authors)