FimH, localized at the distal tips of type 1 pili, bind and cluster unspecified host receptors, possibly concentrated within lipid raft domains (green regions). This triggers a signaling cascade leading to localized rearrangements of F-actin (red), which in turn results in the envelopment and uptake of adherent UPEC. Once internalized, UPEC is trafficked into membrane-bound compartments. From here, undefined signals derived from the host environment (and possibly associated with the host cell differentiation state) trigger UPEC replication, resulting in the formation of intracellular bacterial communities (IBCs) and the eventual efflux of UPEC. Alternatively, UPEC enters a nonreplicating or viable but nonculturable (VBNC) state that can persist for days or weeks, possibly serving as a reservoir for subsequent recurrent acute infections. PIPs phosphoinositides.