In the cystitis subset, a significant difference between hemolysin positive and negative strains was observed, however (P = 0.01, Mann Whitney unpaired test), suggesting that hemolytic cell lysis may contribute to the IL-1β activating virulent phenotype of the acute cystitis strains, for example by assisting the release of IL-1β from cells infected with hemolysin-producing strains. This evidence concerns the gene IL1B and cystitis.