[1] Guys Hosp, Ctr Cardiothorac, London SE1 9RT, England
[2] St Thomas Hosp, Ctr Cardiothorac, London SE1 7EH, England
[3] Taunton & Somerset NHS Trust, Dept Cardiac, Taunton, Somerset, England
[4] John Radcliffe Hosp, Dept Cardiol, Oxford OX3 9DU, England
[5] St James Univ Hosp, Dept Microbiol, Leeds LS9 7TF, W Yorkshire, England
[6] John Radcliffe Hosp, Oxford OX3 9DU, England
[7] Univ Sheffield, Sch Dent, Sheffield, S Yorkshire, England