[1] Univ Tartu, Inst Microbiol, EE-50411 Tartu, Estonia
[2] Univ Padua, Dept Pediat, Neonatal Intens Care Unit, I-35128 Padua, Italy
[3] Univ London, Div Clin Sci, Londo SW17 0RE, England
[4] Univ Clin Tartu, Clin Anaesthesiol & Intens Care, EE-50411 Tartu, Estonia
[5] UCL, Infect Dis & Microbiol Unit, Inst Child Hlth, London WC1N 1EH, England
[6] Univ Milan, Dept Maternal & Pediat Sci, Fdn IRCCS Ca Granda Osped Maggiore Policlin, I-20122 Milan, Italy
[7] INSERM SC10, F-94807 Villejuif, France