[1] JOHN RADCLIFFE HOSP,DEPT GASTROENTEROL,OXFORD OX3 9DU,ENGLAND
[2] JOHN RADCLIFFE HOSP,DEPT IMMUNOL,OXFORD OX3 9DU,ENGLAND
[3] UNIV OXFORD,NUFFIELD DEPT PATHOL & BACTERIOL,OXFORD,ENGLAND
[4] UNIV EDINBURGH,DEPT MED MICROBIOL,EDINBURGH EH8 9YL,MIDLOTHIAN,SCOTLAND