FIG 3 .

Infection with S-CDT-encoding serotypes is associated with activation of the DNA damage response. HeLa cells grown on glass coverslips were infected with Salmonella strains at a multiplicity of infection of approximately 5. Cells were fixed at 48 hpi and were stained with antibodies recognizing 53BP1, γH2AX, and Salmonella cells. DAPI was included as a nucleic acid stain. (A) Representative images for strains FSL S5-0642 (serotype Oranienburg; S-CDT positive) and FSL S5-0415 (serotype Enteritidis; S-CDT negative); data for other strains are shown in Fig. S1 in the supplemental material. Scale bars, 25 μm. (B) A mixed-effects linear model was used to determine whether the proportions of HeLa cells that were positive for 53BP1 and γH2AX foci at 48 hpi differed between S-CDT-positive and -negative serotypes and uninfected controls. Data represent 2 technical replicates from 2 independent experiments for each serotype. The S-CDT-negative bar represents the average of all data for HeLa cells infected with serotypes Typhimurium, Newport, and Enteritidis; the S-CDT-positive bar represents the average for all data for HeLa cells infected with serotypes Javiana, Montevideo, Mississippi, and Oranienburg. ***, P < 0.001; **, P < 0.01. Although the data were transformed for statistical analyses, nontransformed data are shown. Bars represent standard deviations.