[1] Sahlgrens Univ Hosp, Dept Paediat, S-41685 Gothenburg, Sweden
[2] Sahlgrenska Hosp, Dept Otorhinolaryngol, Gothenburg, Sweden
[3] Karolinska Hosp, S-10401 Stockholm, Sweden
[4] Karolinska Inst, Huddinge Hosp, S-10401 Stockholm, Sweden
[5] Skovde Hosp, Skovde, Sweden
[6] Lund Hosp, Lund, Sweden
[7] Boras Hosp, Boras, Sweden
[8] Orebro Hosp, Orebro, Sweden
[9] Dept Clin Microbiol, Orebro, Sweden
[10] Gothenburg Univ, Dept Med Microbiol & Immunol, Gothenburg, Sweden
[11] Natl Publ Hlth Inst, Oulu, Finland