The investigators will recruit from the population of adult users of CISC. The setting is NHS hospitals and community sites throughout the UK where CISC use is taught and/or monitored. The investigators expect to randomise at least 372 participants over a 24 month period. For primary outcome purposes, follow up will continue for 12 months after intervention. Participants will be consented separately to submit an additional urine sample and perianal swab six months after trial completion (18-month timepoint) to assess return to baseline of E. coli ecology. Separate consent will also be asked for permission to access clinical records for extended follow up for a further nine years (ten years in total) and for life-long linkage to central NHS databases. Allowing for a four-month analysis phase, the total planned trial duration is 42 months.