To do so, we infected non-transformed human IMR-90 fibroblasts, classically used to study of cellular senescence, with a pks+ or pks- E. coli strain at various multiplicity of infection (MOI) and followed the presence of DSB detected as nuclear foci positive for the phosphorylated form of the histone H2AX (γH2AX) [25]. Here, H2AX is linked to infection.