Finally, immunocompromised C. elegans pmk-1 and sek-1 mutants are very sensitive to PIA-deficient S. epidermidis, and in sek-1 mutants, in contrast to wild-type nematodes, there is no difference in bacterial titer following infection with PIA-producing and PIA-deficient S. epidermidis strains. Here, MAP2K4 is linked to infection.