Figure 3
Assessment of Ped-2E9 cell cytotoxicity induced by pathogenic Listeria or Bacillus toxin. (a) Quantitative values of the cytotoxicity were calculated by alkaline phosphatase (ALP) released from damaged Ped-2E9 cells resulted from exposure to bacteria cells or toxin preparations (tox). The x axis legends are: LmSA, L. monocytogenes Scott A; LmV7, L. monocytogenes V7; Lin, L. innocua F4247; LmSA (tox), L. monocytogenes Scott A toxin; Lin (tox), L. innocua F4247 toxin preparation; Bc1, B. cereus A926; Bc2, B. cereus MS1-9; Bc3, B. cereus F4810 and Bs, B. subtilis. The percent cytotoxicity was reported based on ALP release which was calculated using formula:
Values are average of two separate experiments carried out in duplicate; values are presented as mean±standard error of mean (s.e.m.). (b) Comparisons of Ped-2E9 cell cytotoxicity induced by Listeria whole cells infected at different multiplicity of infections (MOIs). Cytotoxicity assessment of three different MOIs, 10:1, 50:1 and 100:1 at two different postinfection time points (3 and 6 h). The percent cytotoxicity values (ALP assay) were calculated by the above mentioned formula. Columns, mean; bars, s.e.m. *P<0.05; **P<0.01. (c) Quantitative comparisons of pathogen or toxin induced Ped-2E9 cell cytotoxicity by three methods, laser scanning cytometry (LSC), Typan blue dye exclusion (TB) and ALP release cytotoxicity assay. On y axis, percentage values of gel-entrapped PI-positive Ped-2E9 cells obtained from LSC analysis, reported as LSC (PI+); percent values of Trypan blue-positive Ped-2E9 cell, designated as TB (+); and percent cytotoxicity values (ALP assay) as calculated by the above mentioned formula and designated as Cyt (%). The x axis legends are: uninfected, Ped-2E9 cells which are not infected with pathogens or toxin; Lm V7, L. monocytogenes V7; and Bc toxin, crude toxin preparation from B. cereus MS1-9. The measurements were carried out and reported at 1, 3 and 6 h postinfection. Values are presented as mean±standard error of mean (s.e.m.) of three experiments carried out in duplicate.
