To test whether P. aeruginosa induces Egr-1 expression in macrophages, wild-type bone marrow-derived macrophages (BMMs) were infected with P. aeruginosa 8821 at a multiplicity of infection (MOI) of 10 for 30 min, 1 h, 2 h, or 4 h or were left untreated. Here, EGR1 is linked to infection.