Figure 2
The viability and germination inhibition of C. difficile CCUG 37780 spores by Fe3-δO4 nanoparticles were dose-dependent rather than size-dependent. (A) The spores were first treated for 20 minutes with 500 μg/mL of 22-nm Fe3-δO4 (■), 500 μg/mL of 14-nm Fe3-δO4 (▲), 50 μg/mL of 22-nm Fe3-δO4 (□), 50 μg/mL of 14-nm Fe3-δO4 (▵), or 3% sodium hypochlorite (●) and then were treated with taurocholate to induce germination. Both 14-nm and 22-nm Fe3-δO4 nanoparticles had a similar dose-dependent effect on spore germination. (B) After C. difficile spores and 500 μg/mL of 22-nm Fe3-δO4 nanoparticles or 3% sodium hypochlorite had been incubated for 20 minutes, the spores were plated on BHIS agar for a colony formation assay the next day. The level of colony-forming unit inhibition was similar for Fe3-δO4 nanoparticle- and sodium hypochlorite-treated spores. (C) The spores were treated for 20 minutes with 500 μg/mL of 22-nm Fe3-δO4 and then stimulated using 10 mM taurocholate. After 15 minutes, the phase contrast of the spores was recorded under a phase contrast microscope. (D) The DPA-release assay showed that Fe3-δO4 nanoparticles-treated spores released less DPA than did the control group. Data are mean ± SEM. (***P < 0.001; one-way analysis of variance (ANOVA) followed by Tukey’s Multiple Comparison test).
