[1] Royal Gwent Hosp, Gastroenterol Unit, Newport NP20 2UB, Gwent, Wales
[2] Leeds Teaching Hosp NHS Trust, Microbiol Unit, Leeds, W Yorkshire, England
[3] Norwich & Norfolk Univ Hosp, Gastroenterol Unit, Norwich, Norfolk, England
[4] Southampton Univ Hosp NHS Trust, Wessex Cardiothorac Ctr, Southampton, Hants, England
[5] Norwich & Norfolk Univ Hosp, Dept Cardiol, Norwich, Norfolk, England
[6] Univ Hosp Birmingham NHS Fdn Trust, Birmingham, W Midlands, England